# EDGAR Filing Document

**Accession Number:** 0001321741
**File Stem:** 0001193125-25-269767
**Filing Date:** 2025-11
**Character Count:** 327278
**Document Hash:** 099fc3772918e2c8c551fbc33f8dd8f3
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-25-269767.hdr.sgml**: 20251106

**ACCESSION NUMBER**: 0001193125-25-269767

**CONFORMED SUBMISSION TYPE**: 424B2

**PUBLIC DOCUMENT COUNT**: 12

**FILED AS OF DATE**: 20251106

**DATE AS OF CHANGE**: 20251106

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** GLADSTONE INVESTMENT CORPORATION\DE
- **CENTRAL INDEX KEY:** 0001321741

**ORGANIZATION NAME:**
- **EIN:** 830423116
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 0331

**FILING VALUES:**
- **FORM TYPE:** 424B2
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-277452
- **FILM NUMBER:** 251459032

**BUSINESS ADDRESS:**
- **STREET 1:** 1521 WESTBRANCH DRIVE
- **STREET 2:** SUITE 100
- **CITY:** MCLEAN
- **STATE:** VA
- **ZIP:** 22102
- **BUSINESS PHONE:** 7032875800

**MAIL ADDRESS:**
- **STREET 1:** 1521 WESTBRANCH DRIVE
- **STREET 2:** SUITE 100
- **CITY:** MCLEAN
- **STATE:** VA
- **ZIP:** 22102

?xml version='1.0' encoding='ASCII'? 424B2

##### [**Table of Contents**](#toc)

#### **Table of Contents**

#### Filed Pursuant to Rule 424(b)(2) Registration Statement No. 333-277452

#### PROSPECTUS SUPPLEMENT

#### (To Prospectus dated April 18, 2024)
![](g18863g98x33.jpg)

#### $60,000,000

#### 6.875% Notes due 2028
We are an externally managed, closed-end, non-diversified management investment company that has elected to be regulated as a business development company ("BDC") under the Investment Company Act of 1940, as amended (the "1940 Act"). For federal income tax purposes, we have elected to be treated as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). Our investment objectives are to: (i) achieve and grow current income by investing in debt securities of established businesses that we believe will provide stable earnings and cash flow to pay expenses, make principal and interest payments on our outstanding indebtedness and make distributions to stockholders that grow over time; and (ii) provide our stockholders with long-term capital appreciation in the value of our assets by investing in equity securities of established businesses, generally in combination with the aforementioned debt securities, that we believe can grow over time to permit us to sell our equity investments for capital gains.

We are offering $60.0 million in aggregate principal amount of 6.875% notes due 2028 (the "Notes") in a registered direct offering. The Notes will mature on November 1, 2028. We will pay interest on the Notes on May 1 and November 1 of each year, beginning May 1, 2026. We may redeem the Notes in whole or in part at any time or from time to time, at the redemption price set forth under the section titled "Description of the Notes—Optional Redemption" in this prospectus supplement. In addition, holders of the Notes can require us to repurchase some or all of the Notes at a purchase price equal to 100% of their principal amount, plus accrued and unpaid interest to, but not including, the repurchase date, upon the occurrence of a Change of Control Repurchase Event (as defined herein). The Notes will be issued in minimum denominations of $1,000 and integral multiples of $1,000 in excess thereof.

The Notes will be our direct unsecured obligations and rank equal in right of payment with all outstanding and future unsecured, unsubordinated indebtedness issued by us (including our 5.00% Notes due 2026, our 4.875% Notes due 2028, our 8.00% Notes due 2028 and our 7.875% Notes due 2030 (collectively, the "Existing Notes")). Because the Notes will not be secured by any of our assets, they will be effectively subordinated to any future secured indebtedness of Gladstone Investment Corporation (or any indebtedness that is initially unsecured as to which we subsequently grant a security interest) to the extent of the value of the assets securing such indebtedness. The Notes will be structurally subordinated to all existing and future indebtedness and other obligations of any of our subsidiaries (including borrowings under our revolving credit facility with KeyBank National Association), since the Notes will be obligations exclusively of Gladstone Investment Corporation and not of any of our subsidiaries. The Notes will be senior in right of payment to our common stock and any future outstanding series of our preferred stock. None of our subsidiaries is a guarantor of the Notes and the Notes will not be required to be guaranteed by any subsidiary we may acquire or create in the future.

We do not intend to list the Notes on any securities exchange or automated dealer quotation system.

Investing in the Notes involves a high degree of risk, including the risk of leverage. Before buying any Notes, you should read the material risks described in the "[Supplementary Risk Factors](#supptx18863_4)" section beginning on page S-9 of this prospectus supplement and in the "[Risk Factors](#toc18863_5)" section beginning on page 5 of the accompanying prospectus and under similar headings in the other documents that we file from time to time with the Securities and Exchange Commission (the "SEC"), which are incorporated by reference into this prospectus supplement and the accompanying prospectus.

**THE NOTES ARE NOT DEPOSITS OR OTHER OBLIGATIONS OF A BANK AND ARE NOT INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORATION OR ANY OTHER GOVERNMENT AGENCY.** 

This prospectus supplement, the accompanying prospectus, any free writing prospectus, and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus contain important information you should know before investing in the Notes, including information about risks. Please read these documents before you invest and retain them for future reference. Additional information about us, including our annual, quarterly and current reports, has been filed with the Securities and Exchange Commission (the "SEC") and can be accessed free of charge at its website at www.sec.gov. This information is also available free of charge by calling us collect at (703) 287-5893 or on the Investors section of our corporate website located at www.gladstoneinvestment.com, which, except for the documents incorporated by reference into this prospectus supplement and the accompanying prospectus, is not part of this prospectus supplement nor the accompanying prospectus. You may also call us collect at this number to request other information or to make an investor inquiry. See "Where You Can Find More Information" on page S-39 of this prospectus supplement.

The SEC has not approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

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| | | |
|:---|:---|:---|
|  | Per Note | Total |
| Public offering price | 100.000% | $60000000 |
| Sales load (underwriting discounts and commissions) | 1.500% | $900000 |
| Proceeds, before expenses, to us<sup>(1)</sup> | 98.500% | $59100000 |

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(1) Total expenses of the offering payable by us, excluding underwriting discounts and commissions, are estimated to be $0.4 million. See " Underwriting " on page S-31 of this prospectus supplement.

Delivery of the Notes in book-entry form only through The Depository Trust Company ("DTC") will be made on or about November 10, 2025.

#### Sole Book-Running Manager
B. Riley Securities

#### The date of this prospectus supplement is November 6, 2025

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#### **Table of Contents**

#### **TABLE OF CONTENTS**

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| | |
|:---|:---|
|  | **Page** |
| **Prospectus Supplement** |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[About this Prospectus Supplement](#supptx18863_1) | S-ii |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Prospectus Supplement Summary](#supptx18863_2) | S-1 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[The Offering](#supptx18863_3) | S-4 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Supplementary Risk Factors](#supptx18863_4) | S-9 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Special Note Regarding Forward-Looking Statements](#supptx18863_5) | S-13 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Use of Proceeds](#supptx18863_6) | S-14 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Capitalization](#supptx18863_7) | S-15 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Description of the Notes](#supptx18863_8) | S-16 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Underwriting](#supptx18863_9) | S-31 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Certain United States Federal Income Tax Consequences](#supptx18863_10) | S-34 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Custodian, Transfer Agent, Dividend Disbursing Agent and Paying Agent](#supptx18863_11) | S-39 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Legal Matters](#supptx18863_12) | S-39 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Experts](#supptx18863_13) | S-39 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Where You Can Find More Information](#supptx18863_14) | S-39 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Incorporation by Reference](#supptx18863_15) | S-40 |
| **Prospectus** |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Prospectus Summary](#toc18863_1) | 1 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Fees and Expenses](#toc18863_2) | 5 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Financial Highlights](#toc18863_3) | 5 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Senior Securities](#toc18863_4) | 5 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Risk Factors](#toc18863_5) | 5 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Special Note Regarding Forward-Looking Statements](#toc18863_6) | 6 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Use of Proceeds](#toc18863_7) | 7 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Business](#toc18863_8) | 7 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Management's Discussion and Analysis of Financial Condition and Results of Operations](#toc18863_9) | 7 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Price Range of Common Stock](#toc18863_10) | 7 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Portfolio Companies](#toc18863_11) | 8 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Management](#toc18863_12) | 17 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Portfolio Management](#toc18863_13) | 17 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Control Persons and Principal Stockholders](#toc18863_14) | 20 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Dividend Reinvestment Plan](#toc18863_15) | 21 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Material U.S. Federal Income Tax Considerations](#toc18863_16) | 23 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Description of Our Securities](#toc18863_17) | 30 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Certain Provisions of Delaware Law and of Our Certificate of Incorporation and Bylaws](#toc18863_18) | 34 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Share Repurchases](#toc18863_19) | 38 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Proxy Voting Policies and Procedures](#toc18863_20) | 39 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Plan of Distribution](#toc18863_21) | 40 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Brokerage Allocation and Other Practices](#toc18863_22) | 42 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Custodian, Transfer and Dividend Paying Agent and Registrar](#toc18863_23) | 43 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Legal Matters](#toc18863_24) | 43 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Experts](#toc18863_25) | 43 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Available Information](#toc18863_26) | 43 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Incorporation of Certain Documents by Reference](#toc18863_27) | 44 |

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S-i

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#### **Table of Contents**

#### ABOUT THIS PROSPECTUS SUPPLEMENT
This prospectus supplement, the accompanying prospectus, any free writing prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus set forth the information that you should know before investing in the Notes. You should read these documents, which contain important information, before deciding whether to invest in the Notes.

This prospectus supplement is part of a registration statement on Form N-2 (Registration No. 333-277452) that we have filed with the SEC relating to the securities offered hereby. This prospectus supplement does not contain all of the information that we have included or incorporated by reference in the registration statement and the accompanying exhibits and schedules thereto in accordance with the rules and regulations of the SEC, and we refer you to such omitted information. It is important for you to read and consider all of the information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus before making your investment decision. See "Where You Can Find More Information" in this prospectus supplement.

The distribution of this prospectus supplement and the accompanying prospectus and this offering of the securities may be restricted by law in certain jurisdictions. This prospectus supplement and the accompanying prospectus are not an offer to sell or a solicitation of an offer to buy our Notes in any jurisdiction where such offer or any sale would be unlawful. Persons who come into possession of this prospectus supplement and the accompanying prospectus should inform themselves of and observe any such restrictions.

**We are responsible for the information contained in this prospectus supplement and the accompanying prospectus and the documents incorporated by reference in this prospectus supplement and accompanying prospectus. Neither we nor the underwriter have authorized any other person to provide you with different or inconsistent information, and we take no responsibility for any other information others may give you. The information appearing in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus is accurate only as of the respective dates of such information regardless of the time of delivery or any sale of the Notes. Our business, financial condition, results of operations and prospects may have changed since those dates.** 

S-ii

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#### **Table of Contents**

#### PROSPECTUS SUPPLEMENT SUMMARY
The following summary highlights some of the information contained elsewhere in or incorporated by reference into this prospectus supplement and the accompanying prospectus. It is not complete and may not contain all the information that you may want to consider. You should review the more detailed information contained elsewhere in this prospectus supplement, the accompanying prospectus, any free writing prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying prospectus prior to making an investment in the Notes, and especially the information set forth under the heading "Supplementary Risk Factors" in this prospectus supplement, under the heading "Risk Factors" in the accompanying prospectus and under similar headings in any document incorporated by reference into this prospectus supplement or the accompanying prospectus.

Except where the context suggests otherwise, "Company," "we," "us" or "our" refer to Gladstone Investment Corporation; "Adviser" refers to Gladstone Management Corporation; and "Administrator" refers to Gladstone Administration, LLC.

#### Gladstone Investment Corporation
We were incorporated under the General Corporation Law of the State of Delaware on February 18, 2005. We operate as an externally managed, closed-end, non-diversified management investment company and have elected to be treated as a BDC under the 1940 Act. For U.S. federal income tax purposes, we have elected to be treated as a RIC under Subchapter M of the Code. To continue to qualify as a RIC for U.S. federal income tax purposes and obtain favorable RIC tax treatment, we must meet certain requirements, including certain minimum distribution requirements.

Shares of our common stock, our 5.00% Notes due 2026, our 4.875% Notes due 2028, our 8.00% Notes due 2028 and our 7.875% Notes due 2030 are traded on Nasdaq Global Select Market under the trading symbols "GAIN," "GAINN," "GAINZ," "GAINL" and "GAINI," respectively.

#### Investment Objectives and Strategy
We were established for the purpose of investing in debt and equity securities of established private businesses operating in the United States ("U.S."). Our investment objectives are to: (i) achieve and grow current income by investing in debt securities of established businesses that we believe will provide stable earnings and cash flow to pay expenses, make principal and interest payments on our outstanding indebtedness and make distributions to stockholders that grow over time; and (ii) provide our stockholders with long-term capital appreciation in the value of our assets by investing in equity securities of established businesses, generally in combination with the aforementioned debt securities, that we believe can grow over time to permit us to sell our equity investments for capital gains. To achieve our investment objectives, our investment strategy is to invest in several categories of debt and equity securities, with individual investments generally totaling up to $75 million, although investment size may vary, depending upon our total assets or available capital at the time of investment. We expect that our investment portfolio over time will consist of approximately 75% in debt investments and 25% in equity investments, at cost. As of September 30, 2025, our investment portfolio was comprised of 71.1% in debt investments and 28.9% in equity investments, at cost.

We focus on investing in lower middle market private businesses (which we generally define as private companies with annual earnings before interest, taxes, depreciation and amortization of $4 million to $15 million) in the U.S. that meet certain criteria, including the following: the sustainability of the business' free cash flow and its ability to grow it over time, adequate assets for loan collateral, experienced management teams with a significant ownership interest in the portfolio company, reasonable capitalization of the portfolio company, including an ample equity contribution or cushion based on prevailing enterprise valuation multiples, and the potential to realize appreciation and gain liquidity in our equity position, if any. We anticipate that liquidity in

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#### **Table of Contents**
our equity position will be achieved through a merger, acquisition, or recapitalization of the portfolio company, a public offering of the portfolio company's stock or, to a lesser extent, by exercising our right to require the portfolio company to repurchase our warrants, as applicable, though there can be no assurance that we will always have these rights. We invest in portfolio companies that seek funds for management buyouts and/or growth capital to finance acquisitions, recapitalize or, to a lesser extent, refinance their existing debt facilities. We seek to avoid investing in high-risk, early-stage enterprises.

We invest by ourselves or jointly with other funds and/or management of the portfolio company, depending on the opportunity. In July 2012, the SEC granted us an exemptive order (the "Co-Investment Order") that expanded our ability to co-invest, under certain circumstances, with certain of our affiliates, including Gladstone Capital Corporation, Gladstone Alternative Income Fund and any future BDC or closed-end management investment company that is advised (or sub-advised if it controls the fund) by the Adviser, or any combination of the foregoing, subject to the conditions in the Co-Investment Order. In September 2025, the SEC granted us a new Co-Investment Order that contains a more flexible requirement that allocations be "fair and equitable" to us and that the Adviser consider the interests of us in allocations and which minimizes certain board approval requirements from the prior Co-Investment Order. We believe the Co-Investment Order has enhanced and will continue to enhance our ability to further our investment objectives and strategies. If we are participating in an investment with one or more co-investors, whether or not an affiliate of ours, our investment is likely to be smaller than if we were investing alone.

In general, our investments in debt securities have a term of five years, accrue interest at variable rates based on the 30-day Secured Overnight Financing Rate ("SOFR") and, to a lesser extent, at fixed rates. As of September 30, 2025, our loan portfolio consisted of 100.0% variable rate loans with floors, based on the total principal balance of all outstanding debt investments.

We seek debt instruments that pay interest monthly or, at a minimum, quarterly, and which may include a yield enhancement such as a success fee or, to a lesser extent, deferred interest provision and are primarily interest only, with all principal and any accrued but unpaid interest due at maturity. Generally, success fees accrue at a set rate and are contractually due upon a change of control of the portfolio company. Some debt securities may have deferred interest whereby some portion of the interest payment is added to the principal balance so that the interest is paid, together with the principal, at maturity. This form of deferred interest is often called "paid-in-kind" ("PIK") interest. As of September 30, 2025, we did not have any securities with a PIK feature.

Typically, our investments in equity securities take the form of common stock, preferred stock, limited liability company interests, or warrants or options to purchase any of the foregoing. Often, these equity investments occur in connection with our original investment, buyouts and recapitalizations of a business, or refinancing existing debt. From our initial public offering in 2005 through September 30, 2025, we invested in 65 companies, excluding investments in syndicated loans.

We expect that our investment portfolio will continue to primarily include the following three categories of investments in private companies in the U.S.:

• Secured First Lien Debt Securities: We seek to invest a portion of our assets in secured first lien debt securities also known as senior loans, senior term loans, lines of credit and senior notes. Using its assets as collateral, the borrower typically uses secured first lien debt to cover a substantial portion of the funding needs of the business. These debt securities usually take the form of first priority liens on all, or substantially all, of the assets of the business.

• Secured Second Lien Debt Securities: We seek to invest a portion of our assets in secured second lien debt securities, which may also be referred to as subordinated loans, subordinated notes and mezzanine loans. These secured second lien debt securities rank junior to the borrower's secured first lien debt securities and may be secured by second priority liens on all or a portion of the assets of the business. Additionally, we may receive other yield enhancements in addition to or in lieu of success fees, such as

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warrants to buy common and preferred stock or limited liability interests, in connection with these secured second lien debt securities.

• Preferred and Common Equity/Equivalents: We seek to invest a portion of our assets in equity securities, which consist of preferred and common equity, limited liability company interests, warrants or options to acquire such securities, and are generally in combination with our debt investment in a business. Additionally, we may receive equity investments derived from restructurings on some of our existing debt investments. In many cases, we will own a significant portion of the equity of the businesses in which we invest.

Under the 1940 Act, we may not acquire any asset other than assets of the type listed in Section 55(a) of the 1940 Act, which are referred to as "qualifying assets" and generally include each of the investment types listed above, unless, at the time the acquisition is made, qualifying assets (other than certain assets related to our operations) represent at least 70.0% of our total assets. See "— Regulation as a BDC — Qualifying Assets" in our most recently filed Annual Report on Form 10-K for a discussion of the types of qualifying assets in which we are permitted to invest pursuant to Section 55(a) of the 1940 Act.

We expect that most, if not all, of the debt securities we acquire will not be rated by a rating agency. Investors should assume that these loans would be rated below what is considered "investment grade" quality. Investments rated below investment grade are often referred to as high yield securities or junk bonds and may be considered higher risk as compared to investment grade debt instruments.

#### Investment Adviser and Administrator
We are externally managed by the Adviser, an affiliate of ours and an SEC-registered investment adviser, pursuant to an investment advisory and management agreement. We have also entered into an administration agreement with the Administrator, an affiliate of ours and the Adviser. Each of the Adviser and the Administrator is a privately-held company that is indirectly owned by David Gladstone, our chairman and chief executive officer. Mr. Gladstone also serves on the board of directors of the Adviser, the board of managers of the Administrator, and as an executive officer of the Adviser and the Administrator. The Administrator employs, among others, our chief financial officer and treasurer, chief valuation officer, chief compliance officer, co-general counsels and co-secretaries and their respective staffs. The Adviser and Administrator have extensive experience in our lines of business and also provide investment advisory and administrative services, respectively, to our affiliates, including: Gladstone Commercial Corporation, a publicly-traded real estate investment trust; Gladstone Capital Corporation, a publicly-traded BDC and RIC; Gladstone Land Corporation, a publicly-traded real estate investment trust; and Gladstone Alternative Income Fund, a registered, non-diversified, closed-end management investment company that operates as an interval fund. In the future, the Adviser and Administrator may provide investment advisory and administrative services, respectively, to other funds and companies, both public and private.

The Adviser was organized as a corporation under the laws of the State of Delaware on July 2, 2002 and is a registered investment adviser under the Investment Advisers Act of 1940, as amended. The Administrator was organized as a limited liability company under the laws of the State of Delaware on March 18, 2005. The Adviser and Administrator are headquartered in McLean, Virginia, a suburb of Washington, D.C. The Adviser also has offices in several other states.

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#### **Table of Contents**

#### THE OFFERING
This prospectus supplement sets forth certain terms of the Notes that we are offering pursuant to this prospectus supplement and supplements the accompanying prospectus. This section outlines the specific legal and financial terms of the Notes. You should read this section together with the section titled "Description of the Notes" and the more general description of our debt securities in the accompanying prospectus under the heading "Description of Our Securities—Debt Securities" before investing in the Notes.

Issuer Gladstone Investment Corporation

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|:---|:---|
| Title of the securities  | 6.875% Notes due 2028 |

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|:---|:---|
| Aggregate principal amount being offered  | $60000000 |

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|:---|:---|
| Public Offering Price  | 100.000% |

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|:---|:---|
| Principal payable at maturity  | 100% of the aggregate principal amount. The outstanding principal amount of the Notes will be payable on the stated maturity date at the office of the trustee, paying agent and security registrar for the Notes or at such other office as we may designate. |

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No established trading market We do not intend to list the Notes on any securities exchange or automated dealer quotation system. We cannot assure you that a liquid market for the Notes will develop or be maintained.

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|:---|:---|
| Interest rate  | 6.875% per year |

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|:---|:---|
| Yield to Maturity  | 6.875% |

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Day count basis 360-day year of twelve 30-day months

Trade date November 6, 2025

Original issue date November 10, 2025

Stated maturity date November 1, 2028

Date interest starts accruing November 10, 2025

Interest payment dates Each May 1 and November 1, beginning May 1, 2026. If an interest payment date falls on a non-business day, the applicable interest payment will be made on the next business day and no additional interest will accrue as a result of such delayed payment.

Specified currency U.S. Dollars

Ranking of Notes The Notes will be our direct unsecured obligations and will rank:

• pari passu with our existing and future unsecured, unsubordinated indebtedness, including our Existing Notes;

• senior to any series of preferred stock that we may issue in the future;

• senior to any of our future indebtedness that expressly provides it is subordinated to the Notes;

• effectively subordinated to any future secured indebtedness of Gladstone Investment Corporation (including indebtedness that is initially unsecured to which we subsequently grant security), to the extent of the value of the assets securing such indebtedness; and

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#### **Table of Contents**

• structurally subordinated to all existing and future indebtedness and other obligations of any of our subsidiaries, including the approximately $96.9 million in borrowings outstanding as of November 5, 2025 under our Fifth Amended and Restated Credit Agreement with KeyBank National Association, as amended (the "Credit Facility").

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| Denominations  | We will issue the Notes in denominations of $1,000 and integral multiples of $1,000 in excess thereof. |

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Business day Each Monday, Tuesday, Wednesday, Thursday and Friday that is not a day on which banking institutions in New York City or the place of payment are authorized or required by law or executive order to close.

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| Optional redemption  | Prior to August 1, 2028 (three months prior to the maturity date of the Notes) (the "Par Call Date"), we may redeem the Notes at our option, in whole or in part, at any time and from time to time, at a redemption price (expressed as a percentage of principal amount and rounded to three decimal places) equal to the greater of: (1) (a) the sum of the present values of the remaining scheduled payments of principal and interest thereon discounted to the redemption date (assuming the Notes matured on the Par Call Date) on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Rate plus 50 basis points less (b) interest accrued to the date of redemption, and (2) 100% of the principal amount of the Notes to be redeemed, plus, in either case, accrued and unpaid interest thereon to the redemption date. |

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On or after the Par Call Date, we may redeem the Notes, in whole or in part, at any time and from time to time, at a redemption price equal to 100% of the principal amount of the Notes being redeemed plus accrued and unpaid interest thereon to the redemption date.

You may be prevented from exchanging or transferring the Notes when they are subject to redemption. In case any Notes are to be redeemed in part only, the redemption notice will provide that, upon surrender of such Note, you will receive, without a charge, a new Note or Notes of authorized denominations representing the principal amount of your remaining unredeemed Notes. Any exercise of our option to redeem the Notes will be done in compliance with the indenture and the 1940 Act, to the extent applicable.

If we redeem only some of the Notes, the trustee or, with respect to global securities, DTC, will determine the method for selection of the particular Notes to be redeemed, in accordance with the indenture and the 1940 Act, to the extent applicable, and in accordance with the rules of any national securities exchange or quotation system on which the Notes are listed. Unless we default in payment of the redemption price, on and after the date of redemption, interest will cease to accrue on the Notes called for redemption.

Sinking fund The Notes will not be subject to any sinking fund.

Offer to repurchase upon a Change of Control Repurchase Event If a Change of Control Repurchase Event (as defined in the section titled "Description of the Notes" in this prospectus supplement)

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occurs prior to maturity, holders will have the right, at their option, to require us to repurchase for cash some or all of the Notes at a repurchase price equal to 100% of the principal amount of the Notes being repurchased, plus accrued and unpaid interest to, but not including, the repurchase date. <br>

Defeasance The Notes are subject to legal and covenant defeasance by us. See "Description of the Notes—Defeasance" in this prospectus supplement.

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|:---|:---|
| Form of Notes  | The Notes will be represented by global securities that will be deposited and registered in the name of DTC or its nominee. Except in limited circumstances, you will not receive certificates for the Notes. Beneficial interests in the Notes will be represented through book-entry accounts of financial institutions acting on behalf of beneficial owners as direct and indirect participants in DTC. Investors may elect to hold interests in the Notes through either DTC, if they are a participant, or indirectly through organizations which are participants in DTC. |

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Trustee, Paying Agent and Security Registrar UMB Bank, National Association is the trustee, security registrar and paying agent.

Other covenants In addition to standard covenants relating to payment of principal and interest, maintaining an office where payments may be made or the Notes may be surrendered for payment and related matters, the following covenants shall apply to the Notes:

• We agree that for the period of time during which the Notes are outstanding, we will not violate Section 18(a)(1)(A) as modified by Section 61(a)(2) of the 1940 Act or any successor provisions, whether or not we continue to be subject to such provisions of the 1940 Act, but giving effect, in either case, to any exemptive relief granted to us by the SEC. Currently, these provisions generally prohibit us from incurring additional indebtedness, including through the issuance of additional debt securities, unless our asset coverage, as defined in the 1940 Act, equals at least 150% after such borrowings.

• We agree that for the period of time during which Notes are outstanding, we will not declare any dividend (except a dividend payable in our stock), or declare any other distribution, upon a class of our capital stock, or purchase any such capital stock, unless, in every such case, at the time of the declaration of any such dividend or distribution, or at the time of any such purchase, we have an asset coverage, as defined in the 1940 Act, of at least the threshold specified under Section 18(a)(1)(B) as modified by Section 61(a)(2) of the 1940 Act or any successor provisions thereto of the 1940 Act, after deducting the amount of such dividend, distribution or purchase price, as the case may be, and in each case giving effect to any no-action relief granted by the SEC to another BDC and upon which we may reasonably rely (or to us if we determine to seek such similar no-action or other relief) permitting the BDC to declare any cash dividend or

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distribution notwithstanding the prohibition contained in Section 18(a)(1)(B) as modified by Section 61(a)(2) of the 1940 Act, in order to maintain such BDC's status as a RIC under Subchapter M of the Code.

• If, at any time, we are not subject to the reporting requirements of Sections 13 or 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), to file any periodic reports with the SEC, we agree to furnish to holders of the Notes and the trustee, for the period of time during which the Notes are outstanding, our audited annual consolidated financial statements, within 90 days of our fiscal year end, and unaudited interim consolidated financial statements, within 45 days of our fiscal quarter end (other than our fourth fiscal quarter). All such financial statements will be prepared, in all material respects, in accordance with applicable Generally Accepted Accounting Principles in the United States of America ("GAAP").

Events of default The term "Event of Default" in respect of the Notes means any of the following:

• We do not obtain a rating on the Notes from a nationally recognized statistical rating organization by January 9, 2026;

• We do not pay the principal of any Note when due and payable at maturity;

• We do not pay interest on any Note when due and payable, and such default is not cured within 30 days of its due date;

• We remain in breach of any other covenant in respect of the Notes for 60 days after we receive a written notice of default stating we are in breach (the notice must be sent by either the trustee or holders of at least 25% of the principal amount of the outstanding Notes);

• We file for bankruptcy or certain other events of bankruptcy, insolvency or reorganization occur and remain undischarged or unstayed for a period of 90 days; or

• On the last business day of each of twenty-four consecutive calendar months, the Notes have an asset coverage, as defined in the 1940 Act, of less than 100%.

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| | |
|:---|:---|
| Use of Proceeds  | We estimate that the net proceeds we receive from the sale of the $60.0 million aggregate principal amount of Notes in this offering will be approximately $58.7 million after deducting estimated offering expenses of approximately $0.4 million payable by us. |

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We intend to use the net proceeds from this offering to repay a portion of the amount outstanding under the Credit Facility, to fund new investment opportunities, and for other general corporate purposes. As of November 5, 2025, we had approximately $96.9 million of debt outstanding under our Credit Facility. See "Use of Proceeds" on page S-14.

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| | |
|:---|:---|
| Global Clearance and Settlement Procedures  | Interests in the Notes will trade in DTC's Same Day Funds Settlement System, and any permitted secondary market trading activity in such Notes will, therefore, be required by DTC to be settled in immediately available funds. None of us, the Trustee or the paying agent will have any responsibility for the performance by DTC or its participants or indirect participants of their respective obligations under the rules and procedures governing their operations. |

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Governing Law The Notes and the indenture will be governed by and construed in accordance with the laws of the State of New York.

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| | |
|:---|:---|
| Risk Factors  | See "Supplementary Risk Factors" on page S-9 of this prospectus supplement, "Risk Factors" beginning on page 5 of the accompanying prospectus and under similar heading in documents incorporated by reference into this prospectus supplement and the accompanying prospectus for a discussion of risks you should carefully consider before deciding to invest in the Notes. |

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#### SUPPLEMENTARY RISK FACTORS
Investing in the Notes involves a number of significant risks. You should carefully consider the risks described below and all other information contained in this prospectus supplement, the accompanying prospectus, any free writing prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus before making a decision to purchase the Notes. The risks and uncertainties described below are not the only ones facing us. Additional risks and uncertainties not presently known to us, or not presently deemed material by us, may also impair our operations and performance.

If any of the following risks actually occur, our business, financial condition or results of operations could be materially adversely affected. If that happens, our net asset value and the trading price of our securities could decline and you may lose all or part of your investment.

#### Risks Related to the Offering
The Notes will be unsecured and therefore will be effectively subordinated to any secured indebtedness we may incur in the future and will rank pari passu with, or equal to, all outstanding and future unsecured indebtedness, including the Existing Notes, issued by and us and our general liabilities (total liabilities, less debt).

The Notes will not be secured by any of our assets or any of the assets of our subsidiaries. As a result, the Notes are effectively subordinated to any secured indebtedness we may incur in the future (or any indebtedness that is initially unsecured to which we subsequently grant security) to the extent of the value of the assets securing such indebtedness. In any liquidation, dissolution, bankruptcy or other similar proceeding, the holders of any of our existing or future secured indebtedness and the secured indebtedness of our subsidiaries may assert rights against the assets pledged to secure that indebtedness in order to receive full payment of their indebtedness before the assets may be used to pay other creditors, including the holders of the Notes. In addition, the Notes will rank pari passu with, or equal to, all outstanding and future unsecured indebtedness issued by us, including the Existing Notes, and our general liabilities (total liabilities, less debt).

#### The Notes will be structurally subordinated to the indebtedness and other liabilities of our subsidiaries.
The Notes are obligations exclusively of Gladstone Investment Corporation and not of any of our subsidiaries. None of our subsidiaries will be a guarantor of the Notes and the Notes are not required to be guaranteed by any subsidiaries we may acquire or create in the future.

Except to the extent we are a creditor with recognized claims against our subsidiaries, all claims of creditors of our subsidiaries will have priority over our equity interests in such subsidiaries (and therefore the claims of our creditors, including holders of the Notes) with respect to the assets of such subsidiaries. Even if we are recognized as a creditor of one or more of our subsidiaries, our claims would still be effectively subordinated to any security interests in the assets of any such subsidiary and to any indebtedness or other liabilities of any such subsidiary senior to our claims. Consequently, the Notes will be structurally subordinated to all indebtedness and other liabilities of any of our subsidiaries and any subsidiaries that we may in the future acquire or establish. As of November 5, 2025, there was approximately $96.9 million of debt outstanding under the Credit Facility. Borrowings under the Credit Facility are the obligation of Gladstone Business Investment, LLC ("Business Investment"), a wholly-owned subsidiary of ours, and are structurally senior to the Notes. In addition, our subsidiaries may incur substantial additional indebtedness in the future, all of which would be structurally senior to the Notes.

#### The indenture under which the Notes will be issued will contain limited protection for holders of the Notes.
The indenture under which the Notes will be issued offers limited protection to holders of the Notes. The terms of the indenture and the Notes do not restrict our or any of our subsidiaries' ability to engage in, or otherwise be

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#### **Table of Contents**
a party to, a variety of corporate transactions, circumstances or events that could have an adverse impact on your investment in the Notes. In particular, the terms of the indenture and the Notes will not place any restrictions on our or our subsidiaries' ability to:

• issue securities or otherwise incur additional indebtedness or other obligations, including (1) any indebtedness or other obligations that would be equal in right of payment to the Notes, (2) any indebtedness or other obligations that would be secured and therefore rank effectively senior in right of payment to the Notes to the extent of the values of the assets securing such debt, (3) indebtedness of ours that is guaranteed by one or more of our subsidiaries and which therefore is structurally senior to the Notes and (4) securities, indebtedness or obligations issued or incurred by our subsidiaries that would be senior to our equity interests in our subsidiaries and therefore rank structurally senior to the Notes with respect to the assets of our subsidiaries, in each case other than an incurrence of indebtedness or other obligation that would cause a violation of Section 18(a)(1)(A) as modified by Section 61(a)(2) of the 1940 Act or any successor provisions, whether or not we continue to be subject to such provisions of the 1940 Act, which generally prohibit us incurring additional debt or issuing additional debt or preferred securities, unless our asset coverage, as defined in the 1940 Act, equals at least 150% after such incurrence or issuance;

• pay dividends on, or purchase or redeem or make any payments in respect of, capital stock or other securities ranking junior in right of payment to the Notes, including our preferred stock and any subordinated indebtedness, in each case other than dividends, purchases, redemptions or payments that would cause our asset coverage to fall below the threshold specified in Section 18(a)(1)(B) as modified by Section 61(a)(2) of the 1940 Act or any successor provisions thereto, whether or not we are subject to such provisions of the 1940 Act, giving effect to any no-action relief granted by the SEC to another BDC and upon which we may reasonably rely (or to us if we determine to seek such similar SEC no-action or other relief) permitting the BDC to declare any cash dividend or distribution notwithstanding the prohibition contained in Section 18(a)(1)(B) as modified by Section 61(a)(2) of the 1940 Act in order to maintain the BDC's status as a RIC under Subchapter M of the Code;

• pay dividends on, or purchase or redeem or make any payments in respect of, capital stock or other securities ranking junior in right of payment to the Notes, including our preferred stock and any subordinated indebtedness;

• sell assets (other than certain limited restrictions on our ability to consolidate, merge or sell all or substantially all of our assets);

• enter into transactions with affiliates;

• create liens (including liens on the shares of our subsidiaries) or enter into sale and leaseback transactions;

• make investments; or

• create restrictions on the payment of dividends or other amounts to us from our subsidiaries.

Furthermore, the terms of the indenture and the Notes do not protect holders of the Notes in the event that we experience changes (including significant adverse changes) in our financial condition, results of operations or credit ratings, if any, as they do not require that we or our subsidiaries adhere to any financial tests or ratios or specified levels of net worth, revenues, income, cash flow, or liquidity.

Our ability to recapitalize, incur additional debt (including additional debt that matures prior to the maturity of the Notes) and take a number of other actions that are not limited by the terms of the Notes may have important consequences for you as a holder of the Notes, including making it more difficult for us to satisfy our obligations with respect to the Notes or negatively affecting the trading value of the Notes.

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Other debt we issue or incur in the future could contain more protections for its holders than the indenture and the Notes, including additional covenants and events of default. The issuance or incurrence of any such debt with incremental protections could affect the market for, trading levels, and prices of the Notes.

**There is no active trading market for the Notes. If an active trading market does not develop for the Notes, you may not be able to sell them.** 

The Notes are a new issue of debt securities for which there currently is no trading market. We do not intend to list the Notes on any securities exchange or for quotation of the Notes on any automated dealer quotation system. If the Notes are traded after their initial issuance, they may trade at a discount to their initial offering price depending on prevailing interest rates, the market for similar securities, our credit ratings, our financial condition, performance and prospects, general economic conditions or other relevant factors. We cannot assure you that a liquid trading market will develop or be maintained for the Notes, that you will be able to sell your Notes at a particular time or that the price you receive when you sell will be favorable. To the extent an active trading market does not develop, the liquidity and trading price for the Notes may be harmed. Accordingly, you may be required to bear the financial risk of an investment in the Notes for an indefinite period of time.

#### If we default on our obligations to pay our other indebtedness, we may not be able to make payments on the Notes.
Any default under the agreements governing our indebtedness, including a default under the Credit Facility or other indebtedness to which we may be a party, that is not waived by the required lenders or holders, and the remedies sought by the holders of such indebtedness could make us unable to pay principal, premium, if any, and interest on the Notes and substantially decrease the market value of the Notes. If we are unable to generate sufficient cash flow and are otherwise unable to obtain funds necessary to meet required payments of principal, premium, if any, and interest on our indebtedness, or if we otherwise fail to comply with the various covenants, including financial and operating covenants, in the instruments governing our indebtedness, we could be in default under the terms of the agreements governing such indebtedness. In the event of such default, the holders of such indebtedness could elect to declare all the funds borrowed thereunder to be due and payable, together with accrued and unpaid interest, the lenders under the Credit Facility or other debt we may incur in the future could elect to terminate their commitments, cease making further loans and institute foreclosure proceedings against our assets, and we could be forced into bankruptcy or liquidation. If our operating performance declines, we may in the future need to refinance or restructure our debt, including the Notes, sell assets, reduce or delay capital investments, seek to raise additional capital or seek to obtain waivers from the required lenders under the Credit Facility or other debt that we may incur in the future to avoid being in default. If we are unable to implement one or more of these alternatives, we may not be able to meet our payment obligations under the Notes or our other debt. If we breach our covenants under the Credit Facility or other debt and seek a waiver, we may not be able to obtain a waiver from the required lenders or holders. If this occurs, we would be in default under the Credit Facility or other debt, the lenders or holders could exercise their rights as described above, and we could be forced into bankruptcy or liquidation. If we are unable to repay debt, lenders having secured obligations, including the lenders under the Credit Facility, could proceed against the collateral securing the debt. Because the Credit Facility has, and any future credit facilities will likely have, customary cross-default provisions, if the indebtedness under the Notes or the Credit Facility or under any future credit facility is accelerated, we may be unable to repay or finance the amounts due.

#### We may choose to redeem the Notes when prevailing interest rates are relatively low.
The Notes are redeemable in whole or in part upon certain conditions at any time or from time to time at our option. We may choose to redeem the Notes from time to time, especially if prevailing interest rates are lower than the rate borne by the Notes. If prevailing rates are lower at the time of redemption, and we redeem the Notes, you likely would not be able to reinvest the redemption proceeds in a comparable security at an effective interest rate as high as the interest rate on the Notes being redeemed.

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#### **Table of Contents**

#### We may not be able to repurchase the Notes upon a Change of Control Repurchase Event.
We may not be able to repurchase the Notes upon a Change of Control Repurchase Event because we may not have sufficient funds. We would not be able to borrow under our Credit Facility to finance such a repurchase of the Notes, and we expect that any future credit facility would have similar limitations. Upon a Change of Control Repurchase Event, holders of the Notes may require us to repurchase for cash some or all of the Notes at a repurchase price equal to 100% of the aggregate principal amount of the Notes being repurchased, plus accrued and unpaid interest to, but not including, the repurchase date. The terms of our Credit Facility also provide that certain change of control events will constitute an event of default thereunder entitling the lenders to accelerate any indebtedness outstanding under our Credit Facility at that time and to terminate our Credit Facility. Our failure to purchase such tendered Notes upon the occurrence of such Change of Control Repurchase Event would cause an event of default under the indenture governing the Notes and a cross-default under the agreements governing the Credit Facility, which may result in the acceleration of such indebtedness requiring us to repay that indebtedness immediately. If the holders of the Notes exercise their right to require us to repurchase Notes upon a Change of Control Repurchase Event, the financial effect of this repurchase could cause a default under our current and future debt instruments, and we may not have sufficient funds to repay any such accelerated indebtedness. See "Description of the Notes—Offer to Repurchase Upon a Change of Control Repurchase Event" in this prospectus supplement for more information.

**Our management will have broad discretion in the use of the net proceeds from this offering and may allocate the net proceeds from this offering in ways that you and other securityholders may not approve.** 

Our management will have broad discretion in the use of the net proceeds, including for any of the purposes described in the section entitled "Use of Proceeds," and you will not have the opportunity as part of your investment decision to assess whether the net proceeds are being used in ways with which you may not agree or may not otherwise be considered appropriate. Because of the number and variability of factors that will determine our use of the net proceeds from this offering, their ultimate use may vary substantially from their currently intended use. The failure of our management to use these funds effectively could harm our business. Pending their use, we may invest a portion of net proceeds from this offering in short-term, investment-grade, interest-bearing securities. These investments may not yield a favorable return to us or our stockholders.

**A downgrade, suspension or withdrawal of any credit rating assigned by a rating agency to us or the Notes or change in the debt markets could cause the liquidity or market value of the Notes to decline significantly.** 

Any credit rating is an assessment by rating agencies of our ability to pay our debts when due. Consequently, real or anticipated changes in any credit ratings will generally affect the market value of the Notes. These credit ratings may not reflect the potential impact of risks relating to the structure or marketing of the Notes. Credit ratings are not a recommendation to buy, sell or hold any security, and may be revised or withdrawn at any time by the issuing organization in its sole discretion. We have agreed to obtain a credit rating for the Notes by January 9, 2026. Neither we nor any underwriter otherwise undertakes any obligation to obtain or maintain any credit ratings or to advise holders of Notes of any changes in any credit ratings. There can be no assurance that any credit ratings will remain for any given period of time or that such credit ratings will not be lowered or withdrawn entirely by the rating agencies if in their judgment future circumstances relating to the basis of the credit ratings, such as adverse changes in our Company, so warrant. The conditions of the financial markets and prevailing interest rates have fluctuated in the past and are likely to fluctuate in the future, which could have an adverse effect on the market prices of the Notes.

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#### **Table of Contents**

#### SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS
All statements contained in this prospectus supplement or the accompanying prospectus, other than historical facts, may constitute "forward-looking statements." These statements may relate to, among other things, future events or our future operating results, our business prospects and the prospects of our portfolio companies, actual and potential conflicts of interest with the Adviser and its affiliates, the use of borrowed money to finance our investments, the adequacy of our financing sources and working capital, and our ability to co-invest, among other factors. In some cases, you can identify forward-looking statements by terminology such as "estimate," "may," "might," "believe," "will," "provided," "anticipate," "future," "could," "growth," "plan," "project," "intend," "expect," "should," "would," "if," "seek," "possible," "potential," "likely" or the negative or other variations of such terms or comparable terminology. These forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by such forward-looking statements. Such factors include but are not limited to:

• changes in the economy and the capital markets, including stock price volatility, inflation, elevated interest rates, tariffs and trade wars and risks of recession;

• risks associated with negotiation and consummation of pending and future transactions;

• the loss of one or more of our executive officers, in particular David Gladstone or David Dullum;

• changes in our investment objectives and strategy;

• availability, terms (including the possibility of interest rate volatility) and deployment of capital;

• changes in our industry, interest rates, exchange rates or the general economy, including inflation;

• our business prospects and the prospects of our portfolio companies;

• the degree and nature of our competition;

• changes in governmental regulations, tax rates and similar matters;

• our ability to exit investments in a timely manner;

• our ability to maintain our qualification as a RIC and as a BDC; and

• those factors described or incorporated by reference in the " Supplementary Risk Factors " section of this prospectus supplement and under the heading " Risk Factors " in the accompanying prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus.

We caution readers not to place undue reliance on any such forward-looking statements, which speak only as of the date made. Actual results could differ materially from those anticipated in our forward-looking statements and future results could differ materially from historical performance. Except as required by law, we undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, after the date of this prospectus supplement. Although we undertake no obligation to revise or update any forward-looking statements, whether as a result of new information, future events, or otherwise, you are advised to consult any additional disclosures that we may make directly to you or through reports or other documents we have filed, or in the future may file, with the SEC, including subsequent annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K. The forward-looking statements contained or incorporated by reference in this prospectus supplement and the accompanying prospectus are excluded from the safe harbor protection provided by the Private Securities Litigation Reform Act of 1995 and Section 27A of the Securities Act.

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#### **Table of Contents**

#### USE OF PROCEEDS
We estimate that net proceeds from the sale of $60.0 million aggregate principal amount of the Notes in this offering will be approximately $58.7 million after deducting estimated underwriting discounts and commissions and offering expenses of approximately $0.9 million and $0.4 million, respectively, payable by us.

We intend to use the net proceeds from this offering to repay a portion of our outstanding indebtedness under the Credit Facility, to fund new investment opportunities, and for other general corporate purposes. As of November 5, 2025, we had approximately $96.9 million of debt outstanding under the Credit Facility, which has a revolving period end date of October 30, 2026 and maturity date of October 30, 2028. Advances under the Credit Facility generally bear interest at 30-day Term SOFR, subject to a floor of 0.35%, plus 3.15% per annum until October 30, 2026, with the margin then increasing to 3.40% for the period from October 30, 2026 to October 30, 2027, and increasing further to 3.65% thereafter, in each case, with a SOFR credit spread adjustment of 10 basis points. We intend to re-borrow under our Credit Facility to make investments in portfolio companies in accordance with our investment objectives depending on the availability of appropriate investment opportunities consistent with our investment objectives and market conditions and for other general corporate purposes.

Pending such uses, we will invest a portion of the net proceeds of this offering in short-term investments, such as cash and cash equivalents, which we expect will earn yields substantially lower than the interest income that we anticipate receiving in respect of investments in accordance with our investment objectives.

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#### **Table of Contents**

#### CAPITALIZATION
The following table sets forth our capitalization as of September 30, 2025:

• on an actual basis; and

• on an as-adjusted basis to give effect to the sale of $60.0 million aggregate principal amount of the Notes and the application of the estimated net proceeds of the offering, after deducting underwriting discounts and commissions and estimated offering expenses of approximately $0.9 million and $0.4 million, respectively, payable by us. See "*Use of Proceeds*."

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| | | |
|:---|:---|:---|
|  | AS OF SEPTEMBER 30, 2025 | AS OF SEPTEMBER 30, 2025 |
|  | ACTUAL | AS<br>ADJUSTED\* |
|  | (Unaudited) | (Unaudited) |
|  | (Dollars in thousands) | (Dollars in thousands) |
| Borrowings |  |  |
| Borrowings under Credit Facility, at cost | $97700 | $39000 |
| Notes payable, net | 456978 | 456978 |
| The Notes  |  | 60000 |
| Total borrowings | 554678 | 555978 |
| Net Assets Applicable to Common Stockholders |  |  |
| Common stock, $.001 par value per share, 100,000,000 shares authorized, actual and as adjusted; 39,591,037 shares issued and outstanding, actual and as adjusted\* | $40 | $40 |
| Capital in excess of par value | 483554 | 483554 |
| Cumulative net unrealized appreciation of investments | 93659 | 93659 |
| Cumulative net unrealized appreciation of other | (353) | (353) |
| Overdistributed net investment income | (20095) | (20095) |
| Accumulated net realized loss in excess of distributions | (20962) | (20962) |
| Total Net Assets Available to Common Stockholders | 535843 | 535843 |
| Total Capitalization | 1090521 | 1091821 |

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\* None of these outstanding shares are held by us or for our account.

\*\* Assumes a total of $0.9 million of aggregate underwriting discounts and commissions and $0.4 million of estimated offering costs payable by us in connection with this offering will be capitalized and amortized over the life of the Notes. 

The following are our outstanding classes of securities as of September 30, 2025.

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| | | | |
|:---|:---|:---|:---|
| TITLE OF CLASS | AMOUNT<br> AUTHORIZED | AMOUNT HELD<br> BY US OR<br> FOR OUR<br> ACCOUNT | AMOUNT<br> OUTSTANDING<br> (EXCLUSIVE<br> OF AMOUNTS<br> HELD BY US<br> OR FOR OUR<br> ACCOUNT) |
| Common Stock | 100,000,000 shares | – | 39591037 |
| 5.00% Notes due 2026 | $127937500 | – $| 127937500 |
| 4.875% Notes due 2028 | $134550000 | – $| 134550000 |
| 8.00% Notes due 2028 | $74750000 | – $| 74750000 |
| 7.875% Notes due 2030 | $126500000 | – $| 126500000 |

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#### **Table of Contents**

#### DESCRIPTION OF THE NOTES
The Notes will be issued under a base indenture dated as of May 22, 2020 and a sixth supplemental indenture thereto to be dated November 10, 2025, between us and UMB Bank, National Association, as trustee. We refer to the indenture and the sixth supplemental indenture collectively as the "indenture" and to UMB Bank, National Association as the "trustee." The Notes are governed by the indenture, as required by federal law for all bonds and notes of companies that are publicly offered. An indenture is a contract between us and the financial institution acting as trustee on your behalf, and is subject to and governed by the Trust Indenture Act of 1939, as amended. The trustee has two main roles. First, the trustee can enforce your rights against us if we default. There are some limitations on the extent to which the trustee acts on your behalf, described in the second paragraph under "—Events of Default—Remedies if an Event of Default Occurs" below. Second, the trustee performs certain administrative duties for us with respect to the Notes.

This section includes a summary description of the material terms of the Notes and the indenture. Because this section is a summary, however, it does not describe every aspect of the Notes and the indenture. We urge you to read the indenture because it, and not this description, defines your rights as a holder of the Notes. The base indenture has been attached as an exhibit to the registration statement of which this prospectus supplement is a part and the sixth supplemental indenture will be attached as an exhibit to a Current Report on Form 8-K, which will be incorporated by reference into this prospectus supplement, in each case, as filed or as will be filed with the SEC. See "Where You Can Find More Information" in this prospectus supplement for information on how to obtain a copy of the indenture.

#### General
The Notes will mature on November 1, 2028. The principal payable at maturity will be 100% of the aggregate principal amount. The interest rate of the Notes is 6.875% per year and will be paid every May 1 and November 1, commencing May 1, 2026, and the regular record dates for interest payments will be every April 15 and October 15, commencing April 15, 2026. If an interest payment date falls on a non-business day, the applicable interest payment will be made on the next business day and no additional interest will accrue as a result of such delayed payment. The initial interest period will be the period from and including November 10, 2025, to, but excluding, the initial interest payment date, and the subsequent interest periods will be the periods from and including an interest payment date to, but excluding, the next interest payment date or the stated maturity date, as the case may be.

We will issue the Notes in denominations of $1,000 and integral multiples of $1,000 in excess thereof. The Notes will not be subject to any sinking fund.

The indenture does not limit the amount of debt (including secured debt) that may be issued by us or our subsidiaries under the indenture or otherwise, but does contain a covenant regarding our asset coverage that would have to be satisfied at the time of our incurrence of additional indebtedness. See "— Covenants" and "— Events of Default." Other than as described under "— Covenants" below, the indenture does not restrict us from paying dividends or issuing or repurchasing our other securities. Other than restrictions described under "— Merger or Consolidation" below, the indenture does not contain any covenants or other provisions designed to afford holders of the Notes protection in the event of a highly leveraged transaction involving us or if our credit rating declines as the result of a takeover, recapitalization, highly leveraged transaction or similar restructuring involving us that could adversely affect your investment in the Notes.

We may, without the consent of the holders of the Notes, issue additional notes under the indenture with the same terms (except for the issue date, public offering price, and if applicable, the initial interest payment date) and with the same CUSIP numbers as the Notes offered hereby in an unlimited aggregate principal amount; provided that such additional notes must be treated as part of the same issue as the Notes offered hereby for federal income tax purposes.

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#### Optional Redemption
Prior to the Par Call Date, we may redeem the Notes at our option, in whole or in part, at any time and from time to time, at a redemption price (expressed as a percentage of principal amount and rounded to three decimal places) equal to the greater of: (1) (a) the sum of the present values of the remaining scheduled payments of principal and interest thereon discounted to the redemption date (assuming the Notes matured on the Par Call Date) on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Rate plus 50 basis points less (b) interest accrued to the date of redemption, and (2) 100% of the principal amount of the Notes to be redeemed, plus, in either case, accrued and unpaid interest thereon to the redemption date.

On or after the Par Call Date, we may redeem the Notes, in whole or in part, at any time and from time to time, at a redemption price equal to 100% of the principal amount of the Notes being redeemed plus accrued and unpaid interest thereon to the redemption date.

"Treasury Rate" means, with respect to any redemption date, the yield determined by us in accordance with the following two paragraphs.

The Treasury Rate shall be determined by us after 4:15 p.m., New York City time (or after such time as yields on U.S. government securities are posted daily by the Board of Governors of the Federal Reserve System), on the third business day preceding the redemption date based upon the yield or yields for the most recent day that appear after such time on such day in the most recent statistical release published by the Board of Governors of the Federal Reserve System designated as "Selected Interest Rates (Daily)—H.15" (or any successor designation or publication) ("H.15") under the caption "U.S. government securities—Treasury constant maturities—Nominal" (or any successor caption or heading) ("H.15 TCM"). In determining the Treasury Rate, we shall select, as applicable: (1) the yield for the Treasury constant maturity on H.15 exactly equal to the period from the redemption date to the Par Call Date (the "Remaining Life"); or (2) if there is no such Treasury constant maturity on H.15 exactly equal to the Remaining Life, the two yields—one yield corresponding to the Treasury constant maturity on H.15 immediately shorter than and one yield corresponding to the Treasury constant maturity on H.15 immediately longer than the Remaining Life—and shall interpolate to the Par Call Date on a straight-line basis (using the actual number of days) using such yields and rounding the result to three decimal places; or (3) if there is no such Treasury constant maturity on H.15 shorter than or longer than the Remaining Life, the yield for the single Treasury constant maturity on H.15 closest to the Remaining Life. For purposes of this paragraph, the applicable Treasury constant maturity or maturities on H.15 shall be deemed to have a maturity date equal to the relevant number of months or years, as applicable, of such Treasury constant maturity from the redemption date.

If on the third business day preceding the redemption date H.15 TCM or any successor designation or publication is no longer published, we shall calculate the Treasury Rate based on the rate per annum equal to the semi-annual equivalent yield to maturity at 11:00 a.m., New York City time, on the second business day preceding such redemption date of the United States Treasury security maturing on, or with a maturity that is closest to, the Par Call Date, as applicable. If there is no United States Treasury security maturing on the Par Call Date but there are two or more United States Treasury securities with a maturity date equally distant from the Par Call Date, one with a maturity date preceding the Par Call Date and one with a maturity date following the Par Call Date, we shall select the United States Treasury security with a maturity date preceding the Par Call Date. If there are two or more United States Treasury securities maturing on the Par Call Date or two or more United States Treasury securities meeting the criteria of the preceding sentence, we shall select from among these two or more United States Treasury securities the United States Treasury security that is trading closest to par based upon the average of the bid and asked prices for such United States Treasury securities at 11:00 a.m., New York City time. In determining the Treasury Rate in accordance with the terms of this paragraph, the semi-annual yield to maturity of the applicable United States Treasury security shall be based upon the average of the bid and asked prices (expressed as a percentage of principal amount) at 11:00 a.m., New York City time, of such United States Treasury security, and rounded to three decimal places.

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Our actions and determinations in determining the redemption price shall be conclusive and binding for all purposes, absent manifest error.

Notice of any redemption will be mailed or electronically delivered (or otherwise transmitted in accordance with the depositary's procedures) at least 10 days but not more than 60 days before the redemption date to each holder of Notes to be redeemed.

In the case of a partial redemption, selection of the Notes for redemption will be made pro rata, by lot or by such other method as the trustee in its sole discretion deems appropriate and fair. No Notes of a principal amount of $1,000 or less will be redeemed in part. If any note is to be redeemed in part only, the notice of redemption that relates to the Note will state the portion of the principal amount of the Note to be redeemed. A new Note in a principal amount equal to the unredeemed portion of the Note will be issued in the name of the holder of the Note upon surrender for cancellation of the original Note. For so long as the Notes are held by DTC (or another depositary), the redemption of the Notes shall be done in accordance with the policies and procedures of the depositary.

Unless we default in payment of the redemption price, on and after the redemption date interest will cease to accrue on the Notes or portions thereof called for redemption.

#### Offer to Repurchase Upon a Change of Control Repurchase Event
If a Change of Control Repurchase Event occurs, unless we have exercised our right to redeem the Notes in full, we will make an offer to each holder of Notes to repurchase all or any part (in minimum denominations of $1,000 and integral multiples of $1,000 principal amount in excess thereof) of that holder's Notes at a repurchase price in cash equal to 100% of the aggregate principal amount of Notes repurchased plus any accrued and unpaid interest on the Notes repurchased to, but not including, the date of purchase. Within 30 days following any Change of Control Repurchase Event or, at our option, prior to any Change of Control, but after the public announcement of the Change of Control, we will mail a notice to each holder describing the transaction or transactions that constitute or may constitute the Change of Control Repurchase Event and offering to repurchase Notes on the payment date specified in the notice, which date will be no earlier than 30 days and no later than 60 days from the date such notice is mailed. The notice shall, if mailed prior to the date of consummation of the Change of Control, state that the offer to purchase is conditioned on the Change of Control Repurchase Event occurring on or prior to the payment date specified in the notice. We will comply with the requirements of Rule 14e-1 promulgated under the Exchange Act and any other securities laws and regulations thereunder to the extent those laws and regulations are applicable in connection with the repurchase of the Notes as a result of a Change of Control Repurchase Event. To the extent that the provisions of any securities laws or regulations conflict with the Change of Control Repurchase Event provisions of the Notes, we will comply with the applicable securities laws and regulations and will not be deemed to have breached our obligations under the Change of Control Repurchase Event provisions of the Notes by virtue of such conflict.

On the Change of Control Repurchase Event payment date, subject to extension if necessary to comply with the provisions of the Investment Company Act and the rules and regulations promulgated thereunder, we will, to the extent lawful:

(1) accept for payment all Notes or portions of Notes properly tendered pursuant to our offer;

(2) deposit with the paying agent an amount equal to the aggregate purchase price in respect of all Notes or portions of Notes properly tendered; and

(3) deliver or cause to be delivered to the trustee the Notes properly accepted, together with an officers' certificate stating the aggregate principal amount of Notes being purchased by us.

We will direct the paying agent in writing to promptly remit to each holder of Notes properly tendered the purchase price for the Notes, and the trustee will promptly authenticate and mail (or cause to be transferred by

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book-entry) to each holder a new Note equal in principal amount to any unpurchased portion of any Notes surrendered; provided that each new Note will be in a minimum principal amount of $1,000 or an integral multiple of $1,000 in excess thereof.

We will not be required to make an offer to repurchase the Notes upon a Change of Control Repurchase Event if a third party makes an offer in the manner, at the times and otherwise in compliance with the requirements for an offer made by us and such third party purchases all Notes properly tendered and not withdrawn under its offer.

The source of funds that will be required to repurchase Notes in the event of a Change of Control Repurchase Event will be our available cash or cash generated from our operations or other potential sources, including funds provided by a purchaser in the Change of Control transaction, borrowings, sales of assets or sales of equity. We cannot assure you that sufficient funds from such sources will be available at the time of any Change of Control Repurchase Event to make required repurchases of Notes tendered. The terms of our Credit Facility also provide that certain change of control events will constitute an event of default thereunder entitling the lenders to accelerate any indebtedness outstanding under our Credit Facility at that time and to terminate the Credit Facility. Our and our subsidiaries' future financing facilities may contain similar provisions or other restrictions. Our failure to purchase such tendered Notes upon the occurrence of such Change of Control Repurchase Event would cause an event of default under the indenture governing the Notes and a cross-default under the Credit Facility, which may result in the acceleration of such indebtedness requiring us to repay that indebtedness immediately. If the holders of the Notes exercise their right to require us to repurchase Notes upon a Change of Control Repurchase Event, the financial effect of this repurchase could cause a default under our future debt instruments, even if the Change of Control Repurchase Event itself would not cause a default. It is possible that we will not have sufficient funds at the time of the Change of Control Repurchase Event to make the required repurchase of the Notes and/or our other debt.

The definition of "Change of Control" includes a phrase relating to the direct or indirect sale, transfer, conveyance or other disposition of "all or substantially all" of our properties or assets and those of our subsidiaries taken as a whole. Although there is a limited body of case law interpreting the phrase "substantially all," there is no precise, established definition of the phrase under applicable law. Accordingly, the ability of a holder of Notes to require us to repurchase the Notes as a result of a sale, transfer, conveyance or other disposition of less than all of our assets and the assets of our subsidiaries taken as a whole to another person or group may be uncertain.

For purposes of the Notes:

"Below Investment Grade Rating Event" means the Notes are downgraded below Investment Grade by the Rating Agency on any date from the date of the public notice of an arrangement that results in a Change of Control until the end of the 60-day period following public notice of the occurrence of a Change of Control (which period shall be extended so long as the rating of the Notes is under publicly announced consideration for possible downgrade by the Rating Agency); provided that a Below Investment Grade Rating Event otherwise arising by virtue of a particular reduction in rating shall not be deemed to have occurred in respect of a particular Change of Control (and thus shall not be deemed a Below Investment Grade Rating Event for purposes of the definition of Change of Control Repurchase Event hereunder) if the Rating Agency making the reduction in rating to which this definition would otherwise apply does not announce or publicly confirm or inform us in writing that the reduction was the result, in whole or in part, of any event or circumstance comprised of or arising as a result of, or in respect of, the applicable Change of Control (whether or not the applicable Change of Control shall have occurred at the time of the Below Investment Grade Rating Event).

"Change of Control" means the occurrence of any of the following:

(1) the direct or indirect sale, lease, transfer, conveyance or other disposition (other than by way of merger or consolidation) in one or a series of related transactions, of all or substantially all of the assets of Gladstone Investment Corporation and its Controlled Subsidiaries taken as a whole to any "person" or

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"group" (as those terms are used in Section 13(d)(3) of the Exchange Act), other than to any Permitted Holders; provided that, for the avoidance of doubt, a pledge of assets pursuant to any secured debt instrument of Gladstone Investment Corporation or its Controlled Subsidiaries shall not be deemed to be any such sale, lease, transfer, conveyance or disposition;

(2) the consummation of any transaction (including, without limitation, any merger or consolidation) the result of which is that any "person" or "group" (as those terms are used in Section 13(d)(3) of the Exchange Act) (other than any Permitted Holders) becomes the "beneficial owner" (as defined in Rules 13d-3 and 13d-5 promulgated under the Exchange Act), directly or indirectly, of more than 50% of the outstanding Voting Stock of Gladstone Investment Corporation, measured by voting power rather than number of shares; or

(3) the approval by Gladstone Investment Corporation's stockholders of any plan or proposal relating to the liquidation or dissolution of Gladstone Investment Corporation.

"Change of Control Repurchase Event" means the occurrence of a Change of Control and a Below Investment Grade Rating Event.

"Controlled Subsidiary" means any subsidiary of Gladstone Investment Corporation, 50% or more of the outstanding equity interests of which are owned by Gladstone Investment Corporation and its direct or indirect subsidiaries and of which Gladstone Investment Corporation possesses, directly or indirectly, the power to direct or cause the direction of the management or policies, whether through the ownership of voting equity interests, by agreement or otherwise.

"Egan-Jones" means Egan-Jones Rating Company or any successor thereto.

"Investment Grade" means a rating of BBB- or better by Egan-Jones (or its equivalent under any successor rating categories of Egan-Jones) (or if such Rating Agency ceases to rate the Notes for reasons outside of our control, the equivalent investment grade credit rating from any Rating Agency selected by us as a replacement Rating Agency).

"Permitted Holders" means (i) us, (ii) one or more of our Controlled Subsidiaries and (iii) the Adviser, any affiliate of the Adviser or any entity that is managed or advised by the Adviser or any of its affiliates.

"Rating Agency" means:

(1) Egan-Jones; and

(2) if Egan-J ones ceases to rate the Notes or fails to make a rating of the Notes publicly available for reasons outside of our control, a "nationally recognized statistical rating organization" as defined in Section 3(a)(62) of the Exchange Act selected by us as a replacement agency for Egan-Jones.

"Voting Stock" as applied to stock of any person, means shares, interests, participations or other equivalents in the equity interest (however designated) in such person having ordinary voting power for the election of a majority of the directors (or the equivalent) of such person, other than shares, interests, participations or other equivalents having such power only by reason of the occurrence of a contingency.

#### Global Securities
Each Note will be issued in book-entry form and represented by a global security that we deposit with and register in the name of DTC or its nominee. A global security may not be transferred to or registered in the name of anyone other than the depositary or its nominee, unless special termination situations arise. As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and holder of all the Notes represented by a global security, and investors will be permitted to own only beneficial interests in a global security. For more information about these arrangements, see "—Book-Entry Procedures" below.

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#### Termination of a Global Security
If a global security is terminated for any reason, interests in it will be exchanged for certificates in non-book-entry form (certificated securities). After that exchange, the choice of whether to hold the certificated Notes directly or in street name will be up to the investor. Investors must consult their own banks or brokers to find out how to have their interests in a global security transferred on termination to their own names, so that they will be holders.

#### Conversion and Exchange
The Notes are not convertible into or exchangeable for other securities.

#### Payment and Paying Agents
We will pay interest to the person listed in the trustee's records as the owner of the Notes at the close of business on a particular day in advance of each due date for interest, even if that person no longer owns the Note on the interest due date (the "record date"). Because we will pay all the interest for an interest period to the holders on the record date, holders buying and selling the Notes must work out between themselves the appropriate purchase price. The most common manner is to adjust the sales price of the Notes to prorate interest fairly between buyer and seller based on their respective ownership periods within the particular interest period. This prorated interest amount is called "accrued interest."

#### Payments on Global Securities
We will make payments on the Notes so long as they are represented by a global security in accordance with the applicable policies of the depositary as in effect from time to time. Under those policies, we will make payments directly to the depositary, or its nominee, and not to any indirect holders who own beneficial interests in the global security. An indirect holder's right to those payments will be governed by the rules and practices of the depositary and its participants, as described under "— Book-Entry Procedures" below.

#### Payments on Certificated Securities
In the event the Notes become represented by certificated securities, we will make payments on the Notes as follows. We will pay interest that is due on an interest payment date to the holder of the Notes as shown on the trustee's records as of the close of business on the regular record date. We will make all payments of principal and premium, if any, by check at the office of the applicable trustee in Kansas City, Missouri and/or at other offices that may be specified in the indenture or a notice to holders against surrender of the Note.

Alternatively, if the holder asks us to do so, we will pay any amount that becomes due on the debt security by wire transfer of immediately available funds to an account at a bank in Kansas City, Missouri, on the due date. To request payment by wire, the holder must give the applicable trustee or other paying agent appropriate transfer instructions at least 15 business days before the requested wire payment is due. In the case of any interest payment due on an interest payment date, the instructions must be given by the person who is the holder on the relevant regular record date. Any wire instructions, once properly given, will remain in effect unless and until new instructions are given in the manner described above.

#### Payment When Offices Are Closed
If any payment is due on the Notes on a day that is not a business day, we will make the payment on the next day that is a business day. Payments made on the next business day in this situation will be treated under the indenture as if they were made on the original due date. Such payment will not result in a default under the Notes or the indenture, and no interest will accrue on the payment amount from the original due date to the next day that is a business day.

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#### Book-entry and other indirect holders should consult their banks or brokers for information on how they will receive payments on the Notes.

#### Events of Default
You will have rights if an Event of Default occurs in respect of the Notes and the Event of Default is not cured, as described later in this subsection.

The term "Event of Default" in respect of the Notes means any of the following:

• We do not obtain a rating on the Notes from a nationally recognized statistical rating organization by January 9, 2026;

• We do not pay the principal of any Note when due and payable at maturity;

• We do not pay interest on any Note when due and payable, and such default is not cured within 30 days of its due date;

• We remain in breach of any other covenant in respect of the Notes for 60 days after we receive a written notice of default stating we are in breach (the notice must be sent by either the trustee or holders of at least 25% of the principal amount of the outstanding Notes);

• We file for bankruptcy or certain other events of bankruptcy, insolvency or reorganization occur and remain undischarged or unstayed for a period of 90 days; or

• On the last business day of each of twenty-four consecutive calendar months, the Notes have an asset coverage (as such term is defined in the 1940 Act) of less than 100%.

An Event of Default for the Notes may, but does not necessarily, constitute an Event of Default for any other series of debt securities issued under the same or any other indenture. The trustee may withhold notice to the holders of the Notes of any default, except in the payment of principal or interest, if it in good faith considers the withholding of notice to be in the best interests of the holders.

Remedies if an Event of Default Occurs

If an Event of Default has occurred and is continuing, the trustee or the holders of not less than 25% in principal amount of the Notes may declare the entire principal amount of all the Notes to be due and immediately payable, but this does not entitle any holder of Notes to any redemption payout or redemption premium. This is called a declaration of acceleration of maturity. In certain circumstances, a declaration of acceleration of maturity may be canceled by the holders of a majority in principal amount of the Notes if (1) we have deposited with the trustee all amounts due and owing with respect to the Notes (other than principal or any payment that has become due solely by reason of such acceleration) and certain other amounts, and (2) any other Events of Default have been cured or waived.

Except in cases of default, where the trustee has some special duties, the trustee is not required to take any action under the indenture at the request of any holders unless the holders offer the trustee indemnity, security or both against costs, expenses and liability reasonably satisfactory to it (called an "indemnity"). If indemnity reasonably satisfactory to the trustee is provided, the holders of a majority in principal amount of the Notes may direct the time, method and place of conducting any lawsuit or other formal legal action seeking any remedy available to the trustee. The trustee may refuse to follow those directions in certain circumstances. No delay or omission in exercising any right or remedy will be treated as a waiver of that right, remedy or Event of Default.

Before you are allowed to bypass the trustee and bring your own lawsuit or other formal legal action or take other steps to enforce your rights or protect your interests relating to the Notes, the following must occur:

• You must give the trustee written notice that an Event of Default has occurred and remains uncured;

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• The holders of at least 25% in principal amount of all the Notes must make a written request that the trustee take action because of the default and must offer the trustee indemnity, security, or both reasonably satisfactory to it against the cost and other liabilities of taking that action;

• The trustee must not have taken action for 60 days after receipt of the above notice and offer of indemnity and/or security; and

• The holders of a majority in principal amount of the Notes must not have given the trustee a direction inconsistent with the above notice during that 60-day period.

However, you are entitled at any time to bring a lawsuit for the payment of money due on your Notes on or after the due date.

Book-entry and other indirect holders should consult their banks or brokers for information on how to give notice or direction to or make a request of the trustee and how to declare or cancel an acceleration of maturity.

Each year, we will furnish to the trustee a written statement of certain of our officers certifying that to their knowledge we are in compliance with the indenture and the Notes, or else specifying any default.

Waiver of Default

The holders of a majority in principal amount of the Notes may waive any past defaults other than a default:

• in the payment of principal (or premium, if any) or interest; or

• in respect of a covenant that cannot be modified or amended without the consent of each holder of the Notes.

#### Merger or Consolidation
Under the terms of the indenture, we are generally permitted to consolidate or merge with another entity. We are also permitted to sell all or substantially all of our assets to another entity. However, we may not take any of these actions unless all the following conditions are met:

• where we merge out of existence or convey or transfer our assets substantially as an entirety, the resulting entity must agree to be legally responsible for our obligations under the Notes;

• immediately after giving effect to the transaction, no default or Event of Default shall have occurred and be continuing; and

• we must deliver certain certificates and documents to the trustee.

An assumption by any person of obligations under the Notes and the indenture might be deemed for federal income tax purposes to be an exchange of the Notes for new Notes by the holders thereof, resulting in recognition of gain or loss for such purposes and possibly other adverse tax consequences to the holders. Holders are urged to consult their tax advisors regarding the tax consequences of such an assumption.

#### Modification or Waiver
There are three types of changes we can make to the indenture and the Notes issued thereunder.

Changes Requiring Your Approval

First, there are changes that we cannot make to your Notes without your specific approval. The following is a list of those types of changes:

• change the stated maturity of the principal of (or premium, if any, on) or any installment of principal of or interest on the Notes;

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• reduce any amounts due on the Notes or reduce the rate of interest on the Notes;

• reduce the amount of principal payable upon acceleration of the maturity of a Note following a default;

• change the place or currency of payment on a Note;

• impair your right to sue for payment;

• reduce the percentage of holders of Notes whose consent is needed to modify or amend the indenture; and

• reduce the percentage of holders of Notes whose consent is needed to waive compliance with certain provisions of the indenture or to waive certain defaults or reduce the percentage of holders of Notes required to satisfy quorum or voting requirements at a meeting of holders of the Notes.

Changes Not Requiring Approval

The second type of change does not require any vote by the holders of the Notes. This type is limited to clarifications and certain other changes that would not adversely affect holders of the Notes in any material respect.

Changes Requiring Majority Approval

Any other change to the indenture and the Notes would require the following approval:

• if the change affects only the Notes, it must be approved by the holders of a majority in principal amount of the Notes; and

• if the change affects more than one series of debt securities issued under the same indenture, it must be approved by the holders of a majority in principal amount of all of the series affected by the change, with all affected series voting together as one class for this purpose.

In each case, the required approval must be given by written consent. The holders of a majority in principal amount of all of the series of debt securities issued under the indenture, voting together as one class for this purpose, may waive our compliance with some of our covenants in that indenture. However, we cannot obtain a waiver of a payment default or of any of the matters covered by the bullet points included above under "— Changes Requiring Your Approval."

Further Details Concerning Voting

When taking a vote, we will use the following rules to decide how much principal to attribute to the Notes:

The Notes will not be considered outstanding, and therefore not eligible to vote, if we have deposited or set aside in trust money for their payment or redemption or if we or any affiliate of ours own any Notes. The Notes will also not be eligible to vote if they have been fully defeased as described later under "— Defeasance — Full Defeasance" below.

We will generally be entitled to set any day as a record date for the purpose of determining the holders of the Notes that are entitled to vote or take other action under the indenture. However, the record date may not be earlier than 30 days before the date of the first solicitation of holders to vote on or take such action and not later than the date such solicitation is completed. If we set a record date for a vote or other action to be taken by holders of the Notes, that vote or action may be taken only by persons who are holders of the Notes on the record date and must be taken within eleven months following the record date.

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**Book-entry and other indirect holders should consult their banks or brokers for information on how approval may be granted or denied if we seek to change the indenture or the Notes or request a waiver.** 

#### Satisfaction and Discharge
The indenture will be discharged and will cease to be of further effect with respect to the Notes when:

• Either

• all the Notes that have been authenticated have been delivered to the trustee for cancellation; or

• all the Notes that have not been delivered to the trustee for cancellation:

• have become due and payable, or

• will become due and payable at their stated maturity within one year, or

• are to be called for redemption within one year,

• and we, in the case of the first, second and third sub-bullets above, have irrevocably deposited or caused to be deposited with the trustee as trust funds in trust solely for the benefit of the holders of the Notes, in amounts as will be sufficient, to pay and discharge the entire indebtedness (including all principal, premium, if any, and interest) on such Notes not previously delivered to the trustee for cancellation (in the case of Notes that have become due and payable on or prior to the date of such deposit) or to the stated maturity or redemption date, as the case may be;

• we have paid or caused to be paid all other sums payable by us under the indenture with respect to the Notes; and

• we have delivered to the trustee an officers' certificate and legal opinion, each stating that all conditions precedent provided for in the indenture relating to the satisfaction and discharge of the indenture and the Notes have been complied with.

#### Defeasance
The following provisions will be applicable to the Notes. "Defeasance" means that, by depositing with a trustee an amount of cash and/or government securities sufficient to pay all principal and interest, if any, on the Notes when due and satisfying any additional conditions noted below, we will be deemed to have been discharged from our obligations under the Notes. In the event of a "covenant defeasance," upon depositing such funds and satisfying similar conditions discussed below we would be released from certain covenants under the indenture relating to the Notes.

#### Covenant Defeasance
Under the indenture, we can make the deposit described below and be released from some of the restrictive covenants in the indenture under which the Notes were issued. This is called "covenant defeasance." In that event, you would lose the protection of those restrictive covenants but would gain the protection of having money and government securities set aside in trust to repay your Notes. In order to achieve covenant defeasance, the following must occur:

• Since the Notes are denominated in U.S. dollars, we must deposit in trust for the benefit of all holders of the Notes a combination of cash and U.S. government or U.S. government agency notes or bonds that will generate enough cash to make interest, principal and any other payments on the Notes on their various due dates;

• We must deliver to the trustee a legal opinion of our counsel confirming that, under current U.S. federal income tax law, we may make the above deposit without causing you to be taxed on the Notes any differently than if we did not make the deposit;

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• We must deliver to the trustee a legal opinion and officers' certificate stating that all conditions precedent to covenant defeasance have been complied with;

• Defeasance must not result in a breach or violation of, or result in a default under, the indenture or any of our other material agreements or instruments; and

• No default or Event of Default with respect to the Notes shall have occurred and be continuing and no defaults or events of default related to bankruptcy, insolvency or reorganization shall occur during the next 90 days.

If we accomplish covenant defeasance, you can still look to us for repayment of the Notes if there were a shortfall in the trust deposit or the trustee is prevented from making payment. In fact, if one of the remaining Events of Default occurred (such as our bankruptcy) and the Notes became immediately due and payable, there might be a shortfall. Depending on the event causing the default, you may not be able to obtain payment of the shortfall.

Full Defeasance

The Notes are subject to full defeasance. Full defeasance means that we can legally release ourselves from all payment and other obligations on the Notes, subject to the satisfaction of certain conditions, including, but not limited to that (a) we have received from, or there has been published by, the Internal Revenue Service (the "IRS") a ruling, or (b) there is a change in U.S. federal income tax law, in either case to the effect that the holders of the Notes and any coupons appertaining thereto will not recognize income, gain or loss for U.S. federal income tax purposes as a result of such defeasance and will be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would have been the case if such defeasance had not occurred (called "full defeasance"), and that we put in place the following other arrangements for you to be repaid:

• Since the Notes are denominated in U.S. dollars, we must deposit in trust for the benefit of all holders of the Notes a combination of money and U.S. government or U.S. government agency notes or bonds that will generate enough cash to make interest, principal and any other payments on the Notes on their various due dates;

• We must deliver to the trustee a legal opinion confirming that there has been a change in current U.S. federal tax law or an IRS ruling that allows us to make the above deposit without causing you to be taxed on the Notes any differently than if we did not make the deposit;

• We must deliver to the trustee a legal opinion and officers' certificate stating that all conditions precedent to defeasance have been complied with;

• Defeasance must not result in a breach or violation of, or constitute a default under, the indenture or any of our other material agreements or instruments; and

• No default or Event of Default with respect to the Notes shall have occurred and be continuing and no defaults or events of default related to bankruptcy, insolvency or reorganization shall occur during the next 90 days.

If we ever did accomplish full defeasance, as described above, you would have to rely solely on the trust deposit for repayment of the Notes. You could not look to us for repayment in the unlikely event of any shortfall. Conversely, the trust deposit would most likely be protected from claims of our lenders and other creditors if we ever became bankrupt or insolvent.

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#### Covenants
In addition to standard covenants relating to payment of principal and interest, maintaining an office where payments may be made or securities can be surrendered for payment and related matters, the following covenants will apply to the Notes:

• We agree that for the period of time during which the Notes are outstanding, we will not violate Section 18(a)(1)(A) as modified by Section 61(a)(2) of the 1940 Act or any successor provisions, whether or not we continue to be subject to such provisions of the 1940 Act, but giving effect, in either case, to any exemptive relief granted to us by the SEC. Currently, these provisions generally prohibit us from incurring additional indebtedness, including through the issuance of additional debt securities, unless our asset coverage, as defined in the 1940 Act, equals at least 150% after such borrowings.

• We agree that for the period of time during which Notes are outstanding, we will not declare any dividend (except a dividend payable in our stock), or declare any other distribution, upon a class of our capital stock, or purchase any such capital stock, unless, in every such case, at the time of the declaration of any such dividend or distribution, or at the time of any such purchase, we have an asset coverage, as defined in the 1940 Act, of at least the threshold specified under Section 18(a)(1)(B) as modified by Section 61(a)(2) of the 1940 Act or any successor provisions thereto of the 1940 Act, after deducting the amount of such dividend, distribution or purchase price, as the case may be, and in each case giving effect to any no-action relief granted by the SEC to another BDC and upon which we may reasonably rely (or to us if we determine to seek such similar no-action or other relief) permitting the BDC to declare any cash dividend or distribution notwithstanding the prohibition contained in Section 18(a)(1)(B) as modified by Section 61(a)(2) of the 1940 Act, in order to maintain such BDC's status as a RIC under Subchapter M of the Code.

• If, at any time, we are not subject to the reporting requirements of Sections 13 or 15(d) of the Exchange Act to file any periodic reports with the SEC, we agree to furnish to holders of the Notes and the trustee, for the period of time during which the Notes are outstanding, our audited annual consolidated financial statements, within 90 days of our fiscal year end, and unaudited interim consolidated financial statements, within 45 days of our fiscal quarter end (other than our fourth fiscal quarter). All such financial statements will be prepared, in all material respects, in accordance with applicable GAAP.

#### Form, Exchange and Transfer of Certificated Registered Securities
If registered Notes cease to be issued in book-entry form, they will be issued:

• only in fully registered certificated form;

• without interest coupons; and

• unless we indicate otherwise, in denominations of $1,000 and amounts that are multiples of $1,000.

Holders may exchange their certificated securities for Notes of smaller denominations or combined into fewer Notes of larger denominations, as long as the total principal amount is not changed and as long as the denomination is equal to or greater than $1,000.

Holders may exchange or transfer their certificated securities at the office of the trustee. We have appointed the trustee to act as our agent for registering Notes in the names of holders transferring Notes. We may appoint another entity to perform these functions or perform them ourselves.

Holders will not be required to pay a service charge to transfer or exchange their certificated securities, but they may be required to pay any tax (including a withholding tax) or other governmental charge associated with the transfer or exchange. The transfer or exchange will be made only if our transfer agent is satisfied with the holder's proof of legal ownership.

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We may appoint additional transfer agents or cancel the appointment of any particular transfer agent. We may also approve a change in the office through which any transfer agent acts.

If any certificated securities of a particular series are redeemable and we redeem less than all the Notes, we may block the transfer or exchange of those Notes selected for redemption during the period beginning 15 days before the day we mail the notice of redemption and ending on the day of that mailing, in order to freeze the list of holders to prepare the mailing. We may also refuse to register transfers or exchanges of any certificated Notes selected for redemption, except that we will continue to permit transfers and exchanges of the unredeemed portion of any Note that will be partially redeemed.

If registered Notes are issued in book-entry form, only the depositary will be entitled to transfer and exchange the Notes as described in this subsection, since it will be the sole holder of the Notes.

#### Resignation of Trustee
The trustee may resign or be removed with respect to the Notes provided that a successor trustee is appointed to act with respect to the Notes. In the event that two or more persons are acting as trustee with respect to different series of indenture securities under the indenture, each of the trustees will be a trustee of a trust separate and apart from the trust administered by any other trustee.

#### Governing Law
The indenture and the Notes will be governed by and construed in accordance with the laws of the State of New York.

#### Indenture Provisions—Ranking
The Notes will be our direct unsecured obligations and will rank:

• pari passu with our existing and future unsecured, unsubordinated indebtedness, including the Existing Notes;

• senior to any series of preferred stock that we may issue in the future;

• senior to any of our future indebtedness that expressly provides it is subordinated to the Notes;

• effectively subordinated to any future secured indebtedness of Gladstone Investment Corporation (including indebtedness that is initially unsecured to which we subsequently grant security), to the extent of the value of the assets securing such indebtedness; and

• structurally subordinated to all existing and future indebtedness and other obligations of any of our subsidiaries and any other future subsidiaries of Gladstone Investment, including borrowings under the Credit Facility.

#### The Trustee under the Indenture
UMB Bank, National Association serves as the trustee, paying agent and security registrar under the indenture.

#### Book-Entry Procedures
The Notes will be represented by global securities that will be deposited and registered in the name of DTC or its nominee. This means that, except in limited circumstances, you will not receive certificates for the Notes. Beneficial interests in the Notes will be represented through book-entry accounts of financial institutions acting on behalf of beneficial owners as direct and indirect participants in DTC. Investors may elect to hold interests in the Notes through either DTC, if they are a participant, or indirectly through organizations that are participants in DTC.

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The Notes will be issued as fully registered securities registered in the name of Cede & Co. (DTC's partnership nominee) or such other name as may be requested by an authorized representative of DTC. One fully registered certificate will be issued for each issuance of the Notes, in the aggregate principal amount thereof, and will be deposited with DTC. Interests in the Notes will trade in DTC's Same Day Funds Settlement System, and any permitted secondary market trading activity in such Notes will, therefore, be required by DTC to be settled in immediately available funds. None of the Company, the trustee or the paying agent will have any responsibility for the performance by DTC or its participants or indirect participants of their respective obligations under the rules and procedures governing their operations.

DTC is a limited-purpose trust company organized under the New York Banking Law, a "banking organization" within the meaning of the New York Banking Law, a member of the Federal Reserve System, a "clearing corporation" within the meaning of the New York Uniform Commercial Code, and a "clearing agency" registered pursuant to the provisions of Section 17A of the Exchange Act. DTC holds and provides asset servicing for over 3.5 million issues of U.S. and non-U.S. equity, corporate and municipal debt issues, and money market instruments from over 100 countries that DTC's participants ("Direct Participants") deposit with DTC. DTC also facilitates the post-trade settlement among Direct Participants of sales and other securities transactions in deposited securities through electronic computerized book-entry transfers and pledges between Direct Participants' accounts. This eliminates the need for physical movement of securities certificates. Direct Participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations, and certain other organizations. DTC is a wholly owned subsidiary of The Depository Trust & Clearing Corporation ("DTCC").

DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others such as both U.S. and non-U.S. securities brokers and dealers, banks, trust companies and clearing corporations that clear through or maintain a custodial relationship with a Direct Participant, either directly or indirectly ("Indirect Participants"). DTC has a Standard & Poor's Ratings Services' rating of AA+. The DTC Rules applicable to its participants are on file with the SEC. More information about DTC can be found at www.dtcc.com.

Purchases of the Notes under the DTC system must be made by or through Direct Participants, which will receive a credit for the Notes on DTC's records. The ownership interest of each actual purchaser of each security, or the "Beneficial Owner," is in turn to be recorded on the Direct and Indirect Participants' records. Beneficial Owners will not receive written confirmation from DTC of their purchase. Beneficial Owners are, however, expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the Direct or Indirect Participant through which the Beneficial Owner entered into the transaction. Transfers of ownership interests in the Notes are to be accomplished by entries made on the books of Direct and Indirect Participants acting on behalf of Beneficial Owners. Beneficial Owners will not receive certificates representing their ownership interests in the Notes, except in the event that use of the book-entry system for the Notes is discontinued.

To facilitate subsequent transfers, all Notes deposited by Direct Participants with DTC are registered in the name of DTC's partnership nominee, Cede & Co. or such other name as may be requested by an authorized representative of DTC. The deposit of the Notes with DTC and their registration in the name of Cede & Co. or such other DTC nominee do not effect any change in beneficial ownership. DTC has no knowledge of the actual Beneficial Owners of the Notes; DTC's records reflect only the identity of the Direct Participants to whose accounts the Notes are credited, which may or may not be the Beneficial Owners. The Direct and Indirect Participants will remain responsible for keeping account of their holdings on behalf of their customers.

Conveyance of notices and other communications by DTC to Direct Participants, by Direct Participants to Indirect Participants, and by Direct Participants and Indirect Participants to Beneficial Owners will be governed by arrangements among them, subject to any statutory or regulatory requirements as may be in effect from time to time.

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Redemption notices shall be sent to DTC. If less than all of the Notes within an issue are being redeemed, DTC's practice is to determine by lot the amount of the interest of each Direct Participant in such issue to be redeemed.

Redemption proceeds, distributions, and interest payments on the Notes will be made to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC. DTC's practice is to credit Direct Participants' accounts upon DTC's receipt of funds and corresponding detail information from us or the trustee on the payment date in accordance with their respective holdings shown on DTC's records. Payments by Participants to Beneficial Owners will be governed by standing instructions and customary practices, as is the case with securities held for the accounts of customers in bearer form or registered in "street name," and will be the responsibility of such Participant and not of DTC nor its nominee, the trustee, or us, subject to any statutory or regulatory requirements as may be in effect from time to time. Payment of redemption proceeds, distributions, and interest payments to Cede & Co. (or such other nominee as may be requested by an authorized representative of DTC) is the responsibility of us or the trustee, but disbursement of such payments to Direct Participants will be the responsibility of DTC, and disbursement of such payments to the Beneficial Owners will be the responsibility of Direct and Indirect Participants.

DTC may discontinue providing its services as securities depository with respect to the Notes at any time by giving reasonable notice to us or to the trustee. Under such circumstances, in the event that a successor securities depository is not obtained, certificates are required to be printed and delivered. We may decide to discontinue use of the system of book-entry-only transfers through DTC (or a successor securities depository). In that event, certificates will be printed and delivered to DTC.

The information in this section concerning DTC and DTC's book-entry system has been obtained from sources that we believe to be reliable, but we take no responsibility for its accuracy.

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#### UNDERWRITING
Subject to the terms and conditions set forth in an underwriting agreement among us, the Adviser, the Administrator and the underwriter, we have agreed to sell to the underwriter, and the underwriter has agreed to purchase from us, the principal amount of Notes set forth opposite its name below.

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| | |
|:---|:---|
| Underwriter | Principal<br>Amount of Notes |
| B. Riley Securities, Inc. | $60000000 |
| Total | $60000000 |

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Subject to the terms and conditions set forth in the underwriting agreement, the underwriter has agreed to purchase all of the Notes sold under the underwriting agreement if any of the Notes are purchased.

We, the Adviser and the Administrator have agreed to indemnify the underwriter against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriter may be required to make in respect of those liabilities.

The underwriting agreement provides that the obligations of the underwriter to purchase the Notes are subject to approval of legal matters by counsel to the underwriter and certain other conditions, including the receipt by the underwriter of officers' certificates and legal opinions. The underwriter reserves the right to withdraw, cancel or modify offers and to reject orders in whole or in part. Investors must pay for the Notes purchased in this offering on or about November 10, 2025.

#### Commissions and Discounts
An underwriting discount of 1.500% per Note will be paid by us. The underwriter has advised us that it proposes initially to offer the Notes to the public at the public offering price on the cover of this prospectus supplement.

The following table shows the total underwriting discounts and commissions that we are to pay to the underwriter in connection with this offering.

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| | | |
|:---|:---|:---|
|  | Per Note | Total |
| Public offering price | 100.000% | $60000000 |
| Underwriting discounts and commissions | 1.500% | $900000 |
| Proceeds, before expenses | 98.500% | $59100000 |

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The expenses of the offering, not including the underwriting discounts and commissions, are estimated at $0.4 million and are payable by us.

#### No Sales of Similar Securities
We have agreed not to directly or indirectly offer, sell, short sell or otherwise dispose of, or enter into any agreement to offer, sell, short sell or otherwise dispose of, any debt securities issued or guaranteed by us or other securities convertible into or exchangeable or exercisable for debt securities issued or guaranteed by us or derivative of debt securities issued or guaranteed by us for a period of 90 days after the date of this prospectus supplement without first obtaining the written consent of B. Riley Securities, Inc. This consent may be given at any time without public notice.

#### Listing
We do not intend to list the Notes on any securities exchange or automated dealer quotation system.

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No assurance can be given as to the liquidity of, or development of a public trading market for, the Notes. If an active public trading market for the Notes does not develop, the market price and liquidity of the Notes may be adversely affected.

#### Price Stabilization, Short Positions

Any of these activities may cause the price of the Notes to be higher than the price that otherwise would exist in the open market in the absence of such transactions. These transactions may be affected in the over-the-counter market or otherwise and, if commenced, may be discontinued at any time without any notice relating thereto.

Neither we nor the underwriter make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of the Notes. In addition, neither we nor the underwriter make any representation that the underwriter will engage in these transactions or that these transactions, once commenced, will not be discontinued without notice.

#### Other Relationships
The underwriter and its affiliates have provided in the past and may provide from time to time in the future in the ordinary course of their business certain commercial banking, financial advisory, investment banking and other services to us, our portfolio companies or our affiliates for which they have received or will be entitled to receive separate fees. In particular, the underwriter or its affiliates may execute transactions with us, on behalf of us, any of our portfolio companies or our affiliates. In addition, the underwriter or its affiliates may act as arrangers, underwriters or placement agents for companies whose securities are sold to or whose loans are syndicated to us, our portfolio companies or our affiliates.

The underwriter or its affiliates may also trade in our securities, securities of our portfolio companies or other financial instruments related thereto for their own accounts or for the account of others and may extend loans or financing directly or through derivative transactions to us, any of our portfolio companies or our affiliates.

After the date of this prospectus supplement, the underwriter and its affiliates may from time to time obtain information regarding specific portfolio companies or us that may not be available to the general public. Any such information is obtained by the underwriter and its affiliates in the ordinary course of its business and not in connection with the offering of the Notes. In addition, after the offering period for the sale of the Notes, the underwriter or its affiliates may develop analyses or opinions related to us or our portfolio companies and buy or sell interests in one or more of our portfolio companies on behalf of their proprietary or client accounts and may engage in competitive activities. There is no obligation on behalf of these parties to disclose their respective analyses, opinions or purchase and sale activities regarding any portfolio company or regarding us to our noteholders or any other persons.

In the ordinary course of their various business activities, the underwriter and its affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. The

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underwriter and its affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

The principal business addresses of the underwriter is: B. Riley Securities, Inc., 299 Park Avenue, 21<sup>st</sup> Floor, New York, NY 10171.

#### Alternative Settlement Cycle
It is expected that delivery of the Notes will be made against payment therefor on or about November 10, 2025, which is the second business day following the date hereof (such settlement cycle being referred to as "T+2"). Under Rule 15c6-1 under the Exchange Act, trades in the secondary market generally are required to settle in one business day unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade the Notes on any date prior to the first business day before delivery thereof will be required, by virtue of the fact that the Notes initially will settle in T+2, to specify an alternative settlement cycle at the time of any such trade to prevent failed settlement. Purchasers of the Notes who wish to trade the Notes prior to their date of delivery hereunder should consult their own advisors.

#### Other Jurisdictions
Other than in the United States, no action has been taken by us or the underwriter that would permit a public offering of the Notes offered by this prospectus supplement in any jurisdiction where action for that purpose is required. The Notes offered by this prospectus supplement may not be offered or sold, directly or indirectly, nor may this prospectus supplement or any other offering material or advertisements in connection with the offer and sale of any such Notes be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus supplement comes are advised to inform themselves about and to observe any restriction relating to the offering and the distribution of this prospectus supplement. This prospectus supplement and the accompanying prospectus do not constitute an offer to sell or a solicitation of an offer to buy the Notes offered by this prospectus supplement and the accompanying prospectus in any jurisdiction in which such an offer or a solicitation is unlawful.

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#### CERTAIN UNITED STATES FEDERAL INCOME TAX CONSEQUENCES
The following discussion summarizes certain material U.S. federal income tax consequences of acquiring, owning and disposing of the Notes. The discussion is based upon the Code; current, temporary and proposed U.S. Treasury Regulations issued thereunder (the "Treasury Regulations"); the legislative history of the Code; Internal Revenue Service ("IRS") rulings, pronouncements, interpretations and practices; and judicial decisions now in effect, all of which are subject to change at any time. Any such change may be applied retroactively in a manner that could adversely affect a holder of the Notes. This discussion is limited to persons purchasing the Notes for cash at original issue and at the offering price on the cover page of this prospectus supplement. Furthermore, this discussion assumes that each holder holds the Notes as "capital assets" within the meaning of Section 1221 of the Code (generally, property held for investment). It does not reflect every possible tax outcome or consequence that could result from acquiring, owning or disposing of the Notes. For example, special rules not discussed here may apply to you if you are:

• a broker-dealer, dealer or trader in securities or currencies;

• a controlled foreign corporation;

• a passive foreign investment company;

• an S corporation;

• a bank, thrift or other financial institution;

• a regulated investment company, a real estate investment trust or other financial conduit entity (or shareholder of such entity);

• an accrual method taxpayer subject to special tax accounting rules as a result of its use of financial statements;

• an insurance company;

• a tax-exempt organization, private college and university endowments, retirement plan, individual retirement account or tax deferred account;

• subject to the alternative minimum tax provisions of the Code;

• holding the Notes as part of a hedge, straddle, conversion, integrated or other risk reduction or constructive sale transaction;

• holding the Notes through a partnership or other pass-through entity;

• a "United States person" (within the meaning of the Code) whose "functional currency" is not the U.S. dollar; or

• a U.S. expatriate or former long-term resident.

In addition, this discussion does not reflect state, local or non-U.S. tax consequences that may apply to you based on your particular circumstances and residence. This discussion also does not address any U.S. federal tax consequences, such as the estate tax or gift tax, other than U.S. federal income tax consequences. You are urged to consult your tax advisors to determine the tax consequences particular to your situation, including any applicable state, local or foreign income and other tax consequences, which may result from your acquisition, ownership or disposition of the Notes.

As used herein, "U.S. holder" means a beneficial owner of the Notes that is, for U.S. federal income tax purposes:

• an individual who is a citizen or resident of the United States;

• a corporation (or other entity treated as a corporation for U.S. federal income tax purposes) created or organized in or under the laws of the United States, any state thereof or the District of Columbia;

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• an estate, the income of which is subject to U.S. federal income tax regardless of its source; or

• a trust that (1) is subject to the primary supervision of a U.S. court and the control of one or more "United States persons" (within the meaning of the Code) that have the authority to control all substantial decisions of the trust, or (2) has a valid election in effect under applicable Treasury Regulations to be treated as a United States person.

For purposes of this discussion, "non-U.S. holder" means a beneficial owner of the Notes that is neither a U.S. holder nor an entity treated as a partnership for U.S. federal income tax purposes.

If any entity treated as a partnership for U.S. federal income tax purposes holds the Notes, the tax treatment of an owner of such entity generally will depend upon the status of the owner and the activities of the entity. If you are an owner of an entity treated as a partnership for U.S. federal income tax purposes, you are urged to consult your tax advisor regarding the tax consequences of the entity's purchase, ownership and disposition of the Notes. This discussion does not address the special treatment under U.S. federal income tax law that could result if we invested in tax-exempt securities or certain other investment assets.

Prospective holders considering purchasing the Notes are urged to consult their tax advisors concerning the application of the U.S. federal tax laws to their individual circumstances, as well as any consequences to such holders relating to purchasing, owning and disposing of the Notes under the laws of any other taxing jurisdiction.

#### U.S. Holders
If you are not a U.S. holder, this section does not apply to you.

Interest. The following discussion assumes that the Notes will be issued with no original issue discount or a de minimis amount of original issue discount for U.S. federal income tax purposes. A U.S. holder generally will be required to recognize and include in gross income any stated interest as ordinary income at the time it is paid or accrued on the Notes in accordance with such U.S. holder's method of accounting for U.S. federal income tax purposes.

Sale or other taxable disposition of the Notes. A U.S. holder will recognize gain or loss on the sale, exchange, redemption, retirement or other taxable disposition of a Note equal to the difference, if any, between the sum of the cash and the fair market value of any property received in exchange therefor (less a portion allocable to any accrued and unpaid stated interest, which generally will be taxable as ordinary income if not previously included in such U.S. holder's income) and the U.S. holder's adjusted tax basis in the Note. A U.S. holder's adjusted tax basis in a Note (or a portion thereof) generally will be the U.S. holder's cost therefor. This gain or loss generally will be a capital gain or loss and will be a long-term capital gain or loss if the U.S. holder has held the Notes for more than one year at the time of such disposition. Otherwise, such gain or loss will be a short-term capital gain or loss. In general, long-term capital gains recognized by non-corporate U.S. holders are subject to reduced tax rates. The deductibility of capital losses is subject to limitations under the Code.

Additional tax on net investment income. An additional surtax at a rate of 3.8% is imposed on the amount of "net investment income," in the case of an individual, or undistributed "net investment income," in the case of an estate or trust (other than a charitable trust), which exceeds certain threshold amounts. "Net investment income" as defined for this purpose generally includes interest payments and gain recognized from the sale or other taxable disposition of the Notes. U.S. holders are urged to consult their tax advisors regarding the effect, if any, of this surtax on their ownership and disposition of the Notes.

Information reporting and backup withholding. A U.S. holder may be subject to information reporting and backup withholding when such U.S. holder receives interest payments on the Notes or proceeds upon the sale or other disposition of such Notes (including a redemption or retirement of the Notes). Certain U.S. holders

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(including, among others, corporations and certain tax-exempt organizations) generally are not subject to backup withholding. A U.S. holder will be subject to backup withholding if such holder is not otherwise exempt and any of the following is true.

• such U.S. holder fails to furnish its taxpayer identification number, or "TIN," which, for an individual is ordinarily his or her social security number;

• the IRS notifies the payor that such U.S. holder furnished an incorrect TIN;

• such U.S. holder is notified by the IRS of a failure to properly report payments of interest or dividends; or

• such U.S. holder fails to certify, under penalties of perjury, that such holder has furnished a correct TIN and that the IRS has not notified such U.S. holder that it is subject to backup withholding.

A U.S. holder is urged to consult its tax advisor regarding its qualification for an exemption from backup withholding and the procedures for obtaining such an exemption, if applicable. Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules from a payment to a U.S. holder generally will be allowed as a credit against the U.S. holder's U.S. federal income tax liability or may be refunded, provided the required information is furnished in a timely manner to the IRS.

#### Non-U.S. Holders
If you are not a non-U.S. holder, this section does not apply to you.

Interest. Subject to the discussion below concerning backup withholding and FATCA, interest paid to a non-U.S. holder on its Notes that is not effectively connected with such non-U.S. holder's conduct of a United States trade or business (and, if any applicable treaty so provides, is not attributable to the conduct of a trade or business through a permanent establishment or fixed base in the United States) will not be subject to U.S. federal withholding tax, provided that:

• such holder does not directly or indirectly, actually or constructively, own 10% or more of the total combined voting power of all classes of our voting stock;

• such holder is not a controlled foreign corporation that is related to us through actual or constructive stock ownership, within the meaning of Section 864(d)(4) of the Code;

• such holder is not a bank whose receipt of interest on the Notes is described in Section 881(c)(3)(A) of the Code; and

• either (a) such non-U.S. holder provides its name and address on an applicable IRS Form W-8, and certifies, under penalties of perjury, that it is not a United States person as defined under the Code or (b) such non-U.S. holder holds its Notes through certain foreign intermediaries and satisfies the certification requirements of applicable Treasury Regulations. Special certification rules apply to non-U.S. holders that are pass-through entities rather than corporations or individuals.

A non-U.S. holder generally will also be exempt from withholding tax on interest if such amount is effectively connected with such non-U.S. holder's conduct of a United States trade or business and the non-U.S. holder provides us with appropriate certification (as discussed below under the caption "—United States trade or business").

Subject to the discussion below under "—United States trade or business," if a non-U.S. holder does not satisfy the requirements above, interest paid to such non-U.S. holder generally will be subject to a 30% U.S. federal withholding tax. Such rate may be reduced or eliminated under a tax treaty between the United States and the non-U.S. holder's country of residence. To claim a reduction or exemption under a tax treaty, a non-U.S. holder generally must complete an IRS Form W-8BEN or an IRS Form W-8BEN-E (or applicable successor form) and claim the reduction or exemption on the form.

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Sale or other taxable disposition of the Notes. Subject to the discussion below concerning backup withholding and FATCA, a non-U.S. holder generally will not be subject to U.S. federal income tax or withholding tax on gain recognized on the sale, exchange, redemption, retirement or other taxable disposition of a Note (other than any portion allocable to accrued and unpaid stated interest, which generally will be subject to the discussion above under "—Interest") so long as (i) the gain is not effectively connected with the conduct of a trade of business of the non-U.S. holder in the United States (or, if a tax treaty applies, the gain is not attributable to a United States permanent establishment maintained by such non-U.S. holder) and (ii) in the case of a non-U.S. holder who is an individual, such non-U.S. holder is not present in the United States for 183 days or more in the taxable year of disposition and certain other requirements are not met. A non-U.S. holder who is an individual and does not meet this exemption is urged to consult his or her tax advisor regarding the potential liability for U.S. federal income tax on such holder's gain realized on a Note.

United States trade or business. If interest paid on a Note or gain from a disposition of a Note is effectively connected with a non-U.S. holder's conduct of a United States trade or business (and, if an income tax treaty applies, the non-U.S. holder maintains a United States permanent establishment to which such amounts are generally attributable), the non-U.S. holder generally will be subject to U.S. federal income tax on the interest or gain on a net basis in the same manner as if it were a U.S. holder. If a non-U.S. holder is subject to U.S. federal income tax on the interest on a net income basis, the 30% withholding tax described above will not apply (assuming an appropriate certification is timely provided, generally on IRS Form W-8ECI). A non-U.S. holder that is a corporation may be subject to a branch profits tax equal to 30% of its effectively connected earnings and profits for the taxable year, subject to certain adjustments, unless it qualifies for a lower rate under an applicable income tax treaty.

Backup withholding and information reporting. Interest (including any portion of the proceeds of a sale or other disposition of the Notes allocable to accrued and unpaid stated interest) paid to a non-U.S. holder and the amount of tax, if any, withheld with respect to those payments generally will be reported to the IRS. Copies of the information returns reporting such interest payments and any withholding may also be made available to the tax authorities in the country in which the non-U.S. holder resides under the provisions of an applicable income tax treaty. A non-U.S. holder generally will not be subject to backup withholding with respect to payments on the Notes that we make to the non-U.S. holder, provided that the applicable withholding agent does not have actual knowledge or reason to know that such holder is a "United States person," within the meaning of the Code, and the non-U.S. holder has given us the statement described above under "Non-U.S.Holders—Interest." In addition, a non-U.S. holder will not be subject to backup withholding or information reporting with respect to the proceeds of the sale or other disposition of the Notes (including a retirement or redemption of such Notes) within the United States or conducted through certain U.S.-related brokers, if the payor receives the statement described above and does not have actual knowledge or reason to know that such holder is a United States person or the holder otherwise establishes an exemption. Proceeds of a disposition of a Note paid outside the United States and conducted through a non-U.S. office of a non-U.S. broker generally will not be subject to backup withholding or information reporting.

A non-U.S. holder generally will be entitled to credit any amounts withheld under the backup withholding rules against the holder's U.S. federal income tax liability or may claim a refund provided that the required information is furnished to the IRS in a timely manner.

Foreign Account Tax Compliance Act. Sections 1471 through 1474 of the Code and the Treasury Regulations and other published guidance promulgated thereunder (which are commonly referred to as "FATCA") generally impose withholding taxes on certain types of payments made to non-U.S. financial institutions and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on interest on, or (subject to proposed U.S. Treasury Regulations as discussed below) gross proceeds from the sale or disposition of, the notes paid to a "foreign financial institution" or a "nonfinancial foreign entity" (each as defined in the Code), unless (1) the foreign financial institution undertakes certain diligence and reporting obligations, (2) the non-financial foreign entity either certifies it does not have any "substantial United States owners" (as defined in the Code) or

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furnishes identifying information regarding each substantial United States owner (by providing an IRS Form W-8BEN-E or other applicable IRS form) or (3) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules and provides appropriate documentation (such as an IRS Form W-8BEN-E or other applicable IRS form). If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in (1) above, it must enter into an agreement to with the U.S. Department of Treasury requiring, among other things, that it undertake to identify accounts held by certain "specified United States persons" or "United States-owned foreign entities" (each as defined in the Code), annually report certain information about such accounts and withhold 30% on payments to non-compliant foreign institutions and certain other account holders. Accordingly, the entity through which the Notes are held will affect the determination of whether such withholding is required. An intergovernmental agreement between the United States and an applicable foreign country, or future Treasury Regulations or other guidance, may modify these requirements.

Information reporting requirements may apply regardless of whether withholding is required. Copies of the information returns reporting such interest and withholding also may be made available to the tax authorities in the country in which a non-U.S. holder is a resident under the provisions of an applicable income tax treaty or agreement.

Under the applicable Treasury regulations, withholding under FATCA generally applies to payments of interest on the Notes from such Notes' date of issuance. The U.S. Department of the Treasury has released proposed Treasury Regulations that, if finalized in their present form, would eliminate FATCA withholding tax on gross proceeds from the sale or other disposition of the Notes. In its preamble to the proposed Treasury Regulations, the U.S. Department of the Treasury stated that taxpayers may generally rely on the proposed Treasury Regulations until final Treasury Regulations are issued. Non-U.S. holders are urged to consult with their tax advisors regarding the application of FATCA to their ownership of the Notes. The FATCA withholding tax will apply to all withholdable payments without regard to whether the beneficial owner of the payment would otherwise be entitled to an exemption from imposition of withholding tax pursuant to an applicable tax treaty with the United States or U.S. domestic law. If payment of this withholding tax is made, holders that are otherwise eligible for an exemption from, or reduction of, U.S. federal withholding taxes with respect to such interest (or gross sales proceeds, if the proposed Treasury Regulations are not relied on by the holders) will be required to seek a credit or refund from the IRS to obtain the benefit of such exemption or reduction, if any. We will not pay additional amounts to holders of the Notes in respect of any amounts withheld. Prospective holders are urged to consult their tax advisors regarding the potential application of withholding under FATCA to their investment in the Notes.

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#### CUSTODIAN, TRANSFER AND DIVIDEND PAYING AGENT AND REGISTRAR
The custodian of our assets is The Bank of New York Mellon Corp. The custodian's address is: 500 Ross Street, Suite 935, Pittsburgh, PA 15262. Our assets are held under bank custodianship in compliance with the 1940 Act. Securities held through our wholly owned subsidiary, Business Investment, are held under a custodian agreement with The Bank of New York Mellon Corp., which acts as collateral custodian pursuant to the Credit Facility. The address of the collateral custodian is 2322 French Settlement Road, Suite 100, Dallas, TX 75212. Computershare, Inc. acts as the transfer and dividend paying agent and registrar for our common stock. The principal business address of Computershare Inc. is 150 Royall Street, Canton, Massachusetts 02021, telephone number 781-575-2000. Computershare also maintains an internet website at www.computershare.com.

#### LEGAL MATTERS
Certain legal matters, including the validity of the Notes to be issued in connection with this offering, will be passed upon for us by Kirkland & Ellis LLP, Washington, D.C. Certain legal matters will be passed upon for the underwriter by Duane Morris LLP, New York, New York.

#### EXPERTS
The financial statements incorporated in this prospectus supplement by reference to the Annual Report on Form 10-K for the year ended March 31, 2025 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting. PricewaterhouseCoopers LLP's business address is 655 New York Ave NW, Suite 1100, Washington, District of Columbia 20001.

#### WHERE YOU CAN FIND MORE INFORMATION
This prospectus supplement and the accompanying prospectus constitute part of a registration statement on Form N-2 that we have filed with the SEC, together with any and all amendments and related exhibits under the Securities Act. This prospectus supplement and the accompanying prospectus do not contain all of the information set forth in the registration statement, some of which is contained in exhibits to the registration statement as permitted by the rules and regulations of the SEC. For further information with respect to us and the Notes we are offering under this prospectus supplement and the accompanying prospectus, we refer you to the registration statement, including the exhibits filed as a part of the registration statement. Statements contained in this prospectus supplement and the accompanying prospectus concerning the contents of any contract or any other document are not necessarily complete. If a contract or other document has been filed as an exhibit to the registration statement, please see the copy of the contract or document that has been filed. Each statement in this prospectus supplement and the accompanying prospectus relating to a contract or document filed as an exhibit is qualified in all respects by the filed exhibit.

We file with or submit to the SEC annual, quarterly and current reports, proxy statements and other information meeting the informational requirements of the Exchange Act. This information is available free of charge on the investors section of our website at www.gladstoneinvestment.com. Except for the documents incorporated by reference into this prospectus supplement and the accompanying prospectus, information contained on our website is not incorporated into this prospectus supplement or the accompanying prospectus and you should not consider such information to be part of this prospectus supplement or the accompanying prospectus. The SEC maintains an Internet site that contains reports, proxy and information statements and other information filed electronically by us with the SEC, which are available on the SEC's website free of charge at www.sec.gov. You can request a copy of any of our SEC filings, including those incorporated by reference herein or in the accompanying prospectus, at no cost, by writing or telephoning us at the address or telephone number above.

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#### INCORPORATION BY REFERENCE
SEC rules allow us to "incorporate by reference" the information we file with the SEC, which means that we can disclose important information to you by referring you to those documents filed separately with the SEC. The information incorporated by reference in this prospectus supplement and the accompanying prospectus is considered to be part of this prospectus supplement and the accompanying prospectus, and the information we file subsequently with the SEC prior to the completion of this offering will automatically update and supersede such information.

We previously filed the following documents with the SEC and such filings are incorporated by reference into this prospectus supplement and the accompanying prospectus:

• our Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174125000010/gain-20250331.htm) for the year ended March 31, 2025, filed with the SEC on May 13, 2025 (including portions of our Definitive Proxy Statement for the 2025 Annual Meeting of Stockholders incorporated therein by reference);

• our Quarterly Report on [Form 10-Q](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174125000018/gain-20250630.htm) for the quarter ended June 30, 2025, filed with the SEC on August 12, 2025;

• our Quarterly Report on [Form 10-Q](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174125000022/gain-20250930.htm) for the quarter ended September 30, 2025, filed with the SEC on November 4, 2025; and

• our Current Reports on Form 8-K, filed with the SEC on [June 3, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000119312525134147/d908654d8k.htm) and [August 7, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000119312525175429/d64474d8k.htm) .

We also incorporate by reference into this prospectus supplement additional documents that we may file with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act, from the date of this prospectus supplement until all of the securities offered by this prospectus supplement have been sold or the offering of these securities is otherwise terminated, provided, however, that information "furnished" under Item 2.02 or Item 7.01 of Form 8-K or other information "furnished" to the SEC which is not deemed filed is not incorporated by reference in this prospectus supplement and in the accompanying prospectus. Information that we subsequently file with the SEC as aforesaid will automatically update and may supersede information in this prospectus supplement and the accompanying prospectus and information that we previously filed with the SEC.

You may obtain copies of any of these filings from us as described below, through the SEC or through the SEC's website as described in "*Where You Can Find More Information*." Documents incorporated by reference are available without charge, excluding all exhibits unless an exhibit has been specifically incorporated by reference into this prospectus supplement, by writing or calling our Investor Relations Department at the following address and telephone number.

Investor Relations

Gladstone Investment Corporation

1521 Westbranch Drive, Suite 100

McLean, Virginia 22102

(703) 287-5893

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#### PROSPECTUS
![LOGO](g18863g43q26.jpg)

### $450,000,000

### COMMON STOCK

### PREFERRED STOCK

### DEBT SECURITIES

### SUBSCRIPTION RIGHTS

### WARRANTS
We may offer, from time to time, up to $450,000,000 of our common stock, $0.001 par value per share, preferred stock, $0.001 par value per share, debt securities, subscription rights, warrants representing rights to purchase shares of our common stock, preferred stock or debt securities, or concurrent, separate offerings of these securities (collectively, "Securities"), in one or more offerings. The Securities may be offered at prices and on terms to be disclosed in one or more supplements to this prospectus. In the case of our common stock and warrants or rights to acquire such common stock hereunder, the offering price per share of our common stock by us, less any underwriting commissions or discounts, will not be less than the net asset value per share of our common stock at the time of the offering except (i) in connection with a rights offering to our existing stockholders, (ii) with the consent of the holders of the majority of our outstanding voting securities (as defined in the Investment Company Act of 1940, as amended (the "1940 Act")), or (iii) under such other circumstances as the U.S. Securities and Exchange Commission ("SEC") may permit. You should read this prospectus and the applicable prospectus supplement carefully before you invest in our Securities.

We operate as an externally managed, closed-end, non-diversified management investment company and have elected to be treated as a business development company ("BDC") under the 1940 Act. For federal income tax purposes, we have elected to be treated as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code of 1986, as amended (the "Code"). Our investment objectives are to: (i) achieve and grow current income by investing in debt securities of established businesses that we believe will provide stable earnings and cash flow to pay expenses, make principal and interest payments on our outstanding indebtedness and make distributions to stockholders that grow over time; and (ii) provide our stockholders with long-term capital appreciation in the value of our assets by investing in equity securities of established businesses, generally in combination with the aforementioned debt securities, of established businesses that we believe can grow over time to permit us to sell our equity investments for capital gains.

Our Securities may be offered directly to one or more purchasers, including existing stockholders in a rights offering, through agents designated from time to time by us, or to or through underwriters or dealers, "at-the-market" to or through a market maker into an existing trading market or otherwise directly to one or more purchasers or through agents or through a combination of methods of sale. The prospectus supplement relating to the offering will identify any agents or underwriters involved in the sale of our Securities and will disclose any applicable purchase price, fee, commission or discount arrangement between us and our agents or underwriters or among our underwriters or the basis upon which such amount may be calculated. See "*Plan of Distribution*." We may not sell any of our Securities through agents, underwriters or dealers without delivery of a prospectus supplement describing the method and terms of the offering of such Securities. Our common stock is traded on The Nasdaq Global Select Market under the symbol "GAIN." As of February 23, 2024, the last reported sales price of our common stock was $14.28 per share and the net asset value per share of our common stock on December 31, 2023 (the last date prior to the date of this prospectus as of which we determined our net asset value per share) was $13.01.

**The securities in which we invest generally would be rated below investment grade if they were rated by rating agencies. Below investment grade securities, which are often referred to as "junk," have predominantly speculative characteristics with respect to the issuer's capacity to pay interest and repay principal. They may also be difficult to value and are illiquid.** 

**An investment in our Securities involves certain risks, including, among other things, the risk of leverage and risks relating to investments in securities of small, private and developing businesses. Common shares of closed-end investment companies, including BDCs, frequently trade at a discount to their net asset value per share. If our shares trade at a discount to their net asset value, this will likely increase the risk of loss to purchasers of our shares. You should review carefully the risks and uncertainties, including the risk of leverage and dilution, described in, or incorporated by reference into, the section titled "[Risk Factors](#toc18863_5)" beginning on page 5 of this prospectus or included in, or incorporated by reference into, the applicable prospectus supplement and in any free writing prospectuses we have authorized for use in connection with a specific offering, and under similar headings in the other documents that are incorporated by reference into this prospectus before investing in our securities.** 

This prospectus contains information you should know before investing in our Securities, including information about risks. Please read it before you invest and keep it for future reference. Additional information about us, including our annual, quarterly and current reports, has been filed with the SEC and can be accessed at its website at *www.sec.gov*. This information is also available free of charge or you may make stockholder inquiries by writing to us at Investor Relations, Gladstone Investment Corporation, 1521 Westbranch Drive, Suite 100, McLean, VA 22102, by calling our toll-free investor relations line at 1-866-214-7543 or on our website at *http://www.gladstoneinvestment.com*. See "*Additional Information*." Information contained on our website is not incorporated by reference into this prospectus, and you should not consider that information to be part of this prospectus.

**The SEC has not approved or disapproved these Securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense. This prospectus may not be used to consummate sales of securities unless accompanied by a prospectus supplement.** 

#### April 18, 2024

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#### **TABLE OF CONTENTS**

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| | |
|:---|:---|
|  | **Page** |
|  [Prospectus Summary](#toc18863_1) | 1 |
|  [Fees and Expenses](#toc18863_2) | 5 |
|  [Financial Highlights](#toc18863_3) | 5 |
|  [Senior Securities](#toc18863_4) | 5 |
|  [Risk Factors](#toc18863_5) | 5 |
|  [Special Note Regarding Forward-Looking Statements](#toc18863_6) | 6 |
|  [Use of Proceeds](#toc18863_7) | 7 |
|  [Business](#toc18863_8) | 7 |
|  [Management's Discussion and Analysis of Financial Condition and Results of Operations](#toc18863_9) | 7 |
|  [Price Range of Common Stock](#toc18863_10) | 7 |
|  [Portfolio Companies](#toc18863_11) | 8 |
|  [Management](#toc18863_12) | 17 |
|  [Portfolio Management](#toc18863_13) | 17 |
|  [Control Persons and Principal Stockholders](#toc18863_14) | 20 |
|  [Dividend Reinvestment Plan](#toc18863_15) | 21 |
|  [Material U.S. Federal Income Tax Considerations](#toc18863_16) | 23 |
|  [Description of Our Securities](#toc18863_17) | 30 |
|  [Certain Provisions of Delaware Law and of Our Certificate of Incorporation and Bylaws](#toc18863_18) | 34 |
|  [Share Repurchases](#toc18863_19) | 38 |
|  [Proxy Voting Policies and Procedures](#toc18863_20) | 39 |
|  [Plan of Distribution](#toc18863_21) | 40 |
|  [Brokerage Allocation and Other Practices](#toc18863_22) | 42 |
|  [Custodian, Transfer and Dividend Paying Agent and Registrar](#toc18863_23) | 43 |
|  [Legal Matters](#toc18863_24) | 43 |
|  [Experts](#toc18863_25) | 43 |
|  [Available Information](#toc18863_26) | 43 |
|  [Incorporation of Certain Documents by Reference](#toc18863_27) | 44 |

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**We have not authorized any dealer, salesperson or other person to give any information or to make any representation other than those contained or incorporated by reference in this prospectus or any accompanying supplement to this prospectus. We take no responsibility for any information or representation not contained or incorporated by reference in this prospectus or any accompanying prospectus supplement. This prospectus and any prospectus supplement do not constitute an offer to sell or a solicitation of any offer to buy any security other than the registered securities to which they relate, nor do they constitute an offer to sell or a solicitation of an offer to buy any securities in any jurisdiction to any person to whom it is unlawful to make such an offer or solicitation in such jurisdiction. The information contained or incorporated by reference in this prospectus and any prospectus supplement is accurate as of the dates on their respective covers only. Our business, financial condition, results of operations and prospects may have changed since such dates. We will update these documents to reflect material changes only as required by law.** 

This prospectus is part of a registration statement that we have filed with the SEC using the "shelf" registration process. Under the shelf registration process, we may offer, from time to time, up to $450,000,000 of our Securities on terms to be determined at the time of the offering. This prospectus provides you with a general description of the Securities that we may offer. Each time we use this prospectus to offer Securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained or incorporated by reference in this prospectus. To the extent required by law, we will amend or supplement the information contained or incorporated by reference in this prospectus and any accompanying prospectus supplement to reflect any material changes to such information subsequent to the date of the prospectus and any accompanying prospectus supplement and prior to the completion of any offering pursuant to the prospectus and any accompanying prospectus supplement. Please carefully read this prospectus and any accompanying prospectus supplement together with the additional information described under "*Additional Information*," "*Incorporation of Certain Documents by Reference*" and "*Risk Factors*" before you make an investment decision.

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#### PROSPECTUS SUMMARY
*The following summary highlights some of the information in this prospectus. It is not complete and may not contain all the information that you may want to consider. You should read the entire prospectus and any prospectus supplement carefully, including the section entitled "Risk Factors." Except where the context suggests otherwise, the terms "we," "us," "our," the "Company," and "Gladstone Investment" refer to Gladstone Investment Corporation; "Adviser" refers to Gladstone Management Corporation; "Administrator" refers to Gladstone Administration, LLC; "Gladstone Commercial" refers to Gladstone Commercial Corporation; "Gladstone Capital" refers to Gladstone Capital Corporation; "Gladstone Land" refers to Gladstone Land Corporation; "Gladstone Securities" refers to Gladstone Securities, LLC; and "Affiliated Public Funds" refers collectively to Gladstone Commercial, Gladstone Capital and Gladstone Land.* 

#### General
We were incorporated under the General Corporation Law of the State of Delaware on February 18, 2005. On June 22, 2005, we completed our initial public offering and commenced operations. We operate as an externally managed, closed-end, non-diversified management investment company and have elected to be treated as a BDC under the 1940 Act. For U.S. federal income tax purposes, we have elected to be treated as a RIC under Subchapter M of the Code.

Our shares of common stock, our 5.00% Notes due 2026 ("5.00% 2026 Notes"), our 4.875% Notes due 2028 ("4.875% 2028 Notes") and our 8.00% Notes due 2028 ("8.00% 2028 Notes") are traded on the Nasdaq Global Select Market ("Nasdaq") under the trading symbols "GAIN," "GAINN," "GAINZ" and "GAINL," respectively.

#### Investment Objectives and Strategy
We were established for the purpose of investing in debt and equity securities of established private businesses operating in the United States ("U.S."). Our investment objectives are to: (i) achieve and grow current income by investing in debt securities of established businesses that we believe will provide stable earnings and cash flow to pay expenses, make principal and interest payments on our outstanding indebtedness and make distributions to stockholders that grow over time; and (ii) provide our stockholders with long-term capital appreciation in the value of our assets by investing in equity securities of established businesses, generally in combination with the aforementioned debt securities, that we believe can grow over time to permit us to sell our equity investments for capital gains. To achieve our investment objectives, our investment strategy is to invest in several categories of debt and equity securities, with individual investments generally totaling up to $75 million, although investment size may vary depending upon our total assets or available capital at the time of investment. We expect that our investment portfolio over time will consist of approximately 75% in debt investments and 25% in equity investments, at cost. As of December 31, 2023, our investment portfolio was comprised of 76.6% in debt investments and 23.4% in equity investments, at cost.

We focus on investing in lower middle market private businesses (which we generally define as companies with annual earnings before interest, taxes, depreciation and amortization of $4 million to $15 million) in the U.S. that meet certain criteria, including: the sustainability of the business' free cash flow and its ability to grow it over time, adequate assets for loan collateral, experienced management teams with a significant ownership interest in the portfolio company, reasonable capitalization of the portfolio company, including an ample equity contribution or cushion based on prevailing enterprise valuation multiples, and the potential to realize appreciation and gain liquidity in our equity position, if any. We anticipate that liquidity in our equity position will be achieved through a merger or acquisition of the portfolio company, a public offering of the portfolio company's stock or, to a lesser extent, by exercising our right to require the portfolio company to repurchase our

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warrants, though there can be no assurance that we will always have these rights. We invest in portfolio companies that seek funds for management buyouts and/or growth capital to finance acquisitions, recapitalize or, to a lesser extent, refinance their existing debt facilities. We seek to avoid investing in high-risk, early-stage enterprises.

We invest by ourselves or jointly with other funds and/or management of the portfolio company, depending on the opportunity. In July 2012, the SEC granted us an exemptive order (the "Co-Investment Order") that expanded our ability to co-invest, under certain circumstances, with certain of our affiliates, including Gladstone Capital and any future BDC or closed-end management investment company that is advised (or sub-advised if it controls the fund) by the Adviser, or any combination of the foregoing, subject to the conditions in the Co-Investment Order. We believe the Co-Investment Order has enhanced and will continue to enhance our ability to further our investment objectives and strategies. If we are participating in an investment with one or more co-investors, whether or not an affiliate of ours, our investment is likely to be smaller than if we were investing alone.

In general, our investments in debt securities have a term of five years, accrue interest at variable rates (generally based on one-month term Secured Overnight Financing Rate ("SOFR"), or, historically, the 30-day London Interbank Offered Rate ("LIBOR")) and, to a lesser extent, at fixed rates. We seek debt instruments that pay interest monthly or, at a minimum, quarterly, and which may include a yield enhancement such as a success fee or, to a lesser extent, deferred interest provision and are primarily interest only, with all principal and any accrued but unpaid interest due at maturity. Generally, success fees accrue at a set rate and are contractually due upon a change of control of the portfolio company. Some debt securities may have deferred interest whereby some portion of the interest payment is added to the principal balance so that the interest is paid, together with the principal, at maturity. This form of deferred interest is often called "paid-in-kind" ("PIK") interest. As of December 31, 2023, we did not have any securities with a PIK feature.

Typically, our investments in equity securities take the form of common stock, preferred stock, limited liability company interests, or warrants or options to purchase any of the foregoing. Often, these equity investments occur in connection with our original investment, buyouts and recapitalizations of a business, or refinancing existing debt. From our initial public offering in June 2005 through December 31, 2023, we invested in 58 companies, excluding investments in syndicated loans.

We expect that our investment portfolio will continue to primarily include the following three categories of investments in private companies in the U.S.:

• *Secured First Lien Debt Securities:* We seek to invest a portion of our assets in secured first lien debt securities also known as senior loans, senior term loans, lines of credit and senior notes. Using its assets as collateral, the borrower typically uses secured first lien debt to cover a substantial portion of the funding needs of the business. These debt securities usually take the form of first priority liens on all, or substantially all, of the assets of the business.

• *Secured Second Lien Debt Securities:* We seek to invest a portion of our assets in secured second lien debt securities, which may also be referred to as subordinated loans, subordinated notes and mezzanine loans. These secured second lien debt securities rank junior to the borrower's secured first lien debt securities and may be secured by second priority liens on all or a portion of the assets of the business. Additionally, we may receive other yield enhancements in addition to or in lieu of success fees, such as warrants to buy common and preferred stock or limited liability interests, in connection with these second lien secured debt securities.

• *Preferred and Common Equity/Equivalents:* We seek to invest a portion of our assets in equity securities, which consist of preferred and common equity, limited liability company interests, warrants

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or options to acquire such securities, and are generally in combination with our debt investment in a business. Additionally, we may receive equity investments derived from restructurings on some of our existing debt investments. In many cases, we will own a significant portion of the equity of the businesses in which we invest. <br>

Under the 1940 Act, we may not acquire any asset other than assets of the type listed in Section 55(a) of the 1940 Act, which are referred to as "qualifying assets" and generally include each of the investment types listed above, unless, at the time the acquisition is made, qualifying assets (other than certain assets related to our operations) represent at least 70.0% of our total assets. See "— *Regulation as a BDC — Qualifying Assets*" in our most recently filed Annual Report on Form 10-K for a discussion of the types of qualifying assets in which we are permitted to invest pursuant to Section 55(a) of the 1940 Act.

We expect that most, if not all, of the debt securities we acquire will not be rated by a rating agency. Investors should assume that these loans would be rated below what is considered "investment grade" quality. Investments rated below investment grade are often referred to as high yield securities or junk bonds and may be considered higher risk as compared to investment grade debt instruments.

#### Our Investment Adviser and Administrator
We are externally managed by the Adviser, an affiliate of ours, under an investment advisory and management agreement and another of our affiliates, the Administrator, provides administrative services to us pursuant to a contractual agreement. Each of the Adviser and the Administrator are privately-held companies that are indirectly owned and controlled by David Gladstone, our chairman and chief executive officer. Mr. Gladstone and Terry Lee Brubaker, our chief operating officer, also serve on the board of directors of the Adviser, the board of managers of the Administrator, and as executive officers of the Adviser and the Administrator. The Administrator employs, among others, our chief financial officer and treasurer, chief valuation officer, chief compliance officer, general counsel and secretary (who also serves as the president, general counsel and secretary of the Administrator) and their respective staffs. The Adviser and Administrator have extensive experience in our lines of business and also provide investment advisory and administrative services, respectively, to our affiliates, including the Affiliated Public Funds. In the future, the Adviser and Administrator may provide investment advisory and administrative services, respectively, to other funds and companies, both public and private.

The Adviser was organized as a corporation under the laws of the State of Delaware on July 2, 2002, and is an SEC registered investment adviser under the Investment Advisors Act of 1940, as amended. The Administrator was organized as a limited liability company under the laws of the State of Delaware on March 18, 2005. The Adviser and Administrator are headquartered in McLean, Virginia, a suburb of Washington, D.C., at 1521 Westbranch Drive, McLean, Virginia 22102. The Adviser also has offices in other states.

At a special meeting of stockholders held on January 4, 2024, our stockholders approved a new investment advisory agreement (the "New Advisory Agreement") between us and the Adviser in connection with an anticipated change in control of the Adviser. The Adviser was organized as a corporation under the Delaware General Corporation Law on July 2, 2002. From inception, the Adviser has been 100% indirectly owned and controlled by David Gladstone. David Gladstone owns 100% of the voting and economic interests of The Gladstone Companies, Ltd., which in turn owns 100% of the voting and economic interests of The Gladstone Companies, Inc., which in turn owns 100% of the voting and economic interests of the Adviser. Immediately after approval by the stockholders of Gladstone Capital of a similar proposal on January 24, 2024, the Adviser entered into a voting trust agreement (the "Voting Trust Agreement"), among David Gladstone, Lorna Gladstone, Laura Gladstone, Kent Gladstone and Jessica Martin, each as a trustee and collectively, as the board of trustees of the voting trust (the "Voting Trust Board"), the Adviser and certain stockholders of the Adviser, pursuant to

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which David Gladstone deposited all of his indirect interests in the Adviser, which represented 100% of the voting and economic interests thereof, with the voting trust.

Pursuant to the Voting Trust Agreement, prior to its Effective Date (as defined below) David Gladstone will, in his sole discretion, have the full, exclusive and unqualified right and power to vote in person or by proxy all of the shares of common stock of the Adviser deposited with the voting trust at all meetings of the stockholders of the Adviser in respect of any and all matters on which the stockholders of the Adviser are entitled to vote under the Adviser's certificate of incorporation or applicable law, to give consents in lieu of voting such shares of common stock of the Adviser at a meeting of the stockholders of the Adviser in respect of any and all matters on which stockholders of the Adviser are entitled to vote under its certificate of incorporation or applicable law, to enter into voting agreements, waive notice of any meeting of stockholders of the Adviser in respect of such shares of common stock of the Adviser and to grant proxies with respect to all such shares of common stock of the Adviser with respect to any lawful corporate action (collectively, the "Voting Powers"). Commencing on the Effective Date, the Voting Trust Board shall have the full, exclusive and unqualified right and power to exercise the Voting Powers. Each member of the Voting Trust Board shall hold 20% of the voting power of the Voting Trust Board as of the Effective Date. The "Effective Date" shall occur on the earliest of (i) the death of David Gladstone, (ii) David Gladstone's election (in his sole discretion) and (iii) January 24, 2025 (one year from the date the Voting Trust Agreement is entered into).

As the Effective Date could occur at any time on or before January 24, 2025, for any investor who purchases shares of our capital stock between the date of filing of the registration statement of which this prospectus forms part and the Effective Date, the investment advisory agreement in place at the time of their purchase will automatically terminate on the Effective Date in connection with the change of control and we and the Adviser will enter into the New Advisory Agreement on such date. However, any shares purchased between the filing of the registration statement of which this prospectus forms a part and the Effective Date will not have the right to vote with respect to such change.

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#### FEES AND EXPENSES
The information contained under the caption "*Fees and Expenses*" in Part II. Item 5 of our most recent Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm#ia87130eb6a35479584dd555e26cc92d7_37) is incorporated by reference herein.

#### FINANCIAL HIGHLIGHTS
The information contained in *Note 12. Financial Highlights* to the audited financial statements in Part II. Item 8 of our most recent Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm#ia87130eb6a35479584dd555e26cc92d7_79) is incorporated by reference herein.

#### SENIOR SECURITIES
The information contained under the caption "*Senior Securities*" in Part II. Item 5 of our most recent Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm#ia87130eb6a35479584dd555e26cc92d7_37) is incorporated by reference herein.

#### RISK FACTORS
*An investment in any Securities offered pursuant to this prospectus involves substantial risks. You should carefully consider the risk factors incorporated by reference herein from our most recent Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm#ia87130eb6a35479584dd555e26cc92d7_19) and our subsequent Quarterly Reports on [Form 10-Q](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174124000005/gain-20231231.htm#i1d8f1f06c7844f69bb1da9c01f33f3ee_253) and the other information contained in this prospectus, as updated, amended or superseded by our subsequent filings under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), and the risk factors and other information contained in any accompanying prospectus supplement before acquiring any of such Securities. The occurrence of any of these risks could materially and adversely affect our business, prospects, financial condition, results of operations and cash flow and might cause you to lose all or part of your investment in the offered Securities. Much of the business information, as well as the financial and operational data contained in our risk factors, is updated in our periodic reports filed with the SEC pursuant to the Exchange Act, which are also incorporated by reference into this prospectus. Although we believe the risk factors described in such documents are the principal risk factors associated with an investment in our Securities as well as those factors generally associated with an investment company with investment objectives, investment policies, capital structure or trading markets similar to ours, please be aware that these are not the only risks we face and there may be additional risks that we do not presently know of or that we currently consider not likely to have a significant impact. New risks may emerge at any time and we cannot predict such risks or estimate the extent to which they may affect our business or our financial performance. Please also refer to "Special Note Regarding Forward-Looking Statements."* 

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#### SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS
All statements contained or incorporated by reference in this prospectus or any accompanying prospectus supplement, other than historical facts, may constitute "forward-looking statements." These statements may relate to, among other things, future events or our future operating results, our business prospects and the prospects of our portfolio companies, actual and potential conflicts of interest with the Adviser and its affiliates, the use of borrowed money to finance our investments, the adequacy of our financing sources and working capital, and our ability to co-invest, among other factors. In some cases, you can identify forward-looking statements by terminology such as "estimate," "may," "might," "believe," "will," "provided," "anticipate," "future," "could," "growth," "plan," "project," "intend," "expect," "should," "would," "if," "seek," "possible," "potential," "likely" or the negative or other variations of such terms or comparable terminology. These forward-looking statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by such forward-looking statements. Such factors include:

• changes in the economy and the capital markets;

• risks associated with negotiation and consummation of pending and future transactions;

• the loss of one or more of our executive officers, in particular David Gladstone, David Dullum or Terry Lee Brubaker;

• changes in our investment objectives and strategy;

• availability, terms (including the possibility of interest rate volatility) and deployment of capital;

• changes in our industry, interest rates, exchange rates, regulation or the general economy, including inflation;

• our business prospects and the prospects of our portfolio companies;

• the degree and nature of our competition;

• changes in governmental regulations, tax rates and similar matters;

• our ability to exit investments in a timely manner;

• our ability to maintain our qualification as a RIC and as a BDC; and

• those factors described or incorporated by reference in the "*Risk Factors*" section of this prospectus and any accompanying prospectus supplement.

We caution readers not to place undue reliance on any such forward-looking statements, which speak only as of the date made. Actual results could differ materially from those anticipated in our forward-looking statements and future results could differ materially from our historical performance. Except as required by law, we undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, after the date of this prospectus. Although we undertake no obligation to revise or update any forward-looking statements, whether as a result of new information, future events, or otherwise, you are advised to consult any additional disclosures that we may make directly to you or through reports we have filed, or in the future may file, with the SEC, including annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K. The forward-looking statements contained or incorporated by reference in this prospectus or any accompanying prospectus supplement are excluded from the safe harbor protection provided by the Private Securities Litigation Reform Act of 1995 and Section 27A of the Securities Act of 1933, as amended (the "Securities Act").

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#### USE OF PROCEEDS
Unless otherwise specified in any prospectus supplement accompanying this prospectus, we intend to use the net proceeds from the sale of the Securities first to pay down outstanding debt (which may include borrowings under our revolving credit facility with KeyBank National Association, as administrative agent (as amended, the "Credit Facility")), if any, then to make investments in accordance with our investment objectives and strategy, with any remaining proceeds to be used for other general corporate purposes. We intend to re-borrow under our Credit Facility to make investments in portfolio companies in accordance with our investment objectives and strategy depending on the availability of appropriate investment opportunities and market conditions. We anticipate that substantially all of the net proceeds of any offering of Securities will be utilized in the manner described above within three months of the completion of such offering. Pending such utilization, we intend to invest the net proceeds of any offering of Securities primarily in cash, cash equivalents, U.S. government securities, and other high-quality debt investments that mature in one year or less from the date of investment, consistent with the requirements for continued qualification as a RIC for federal income tax purposes. These temporary investments may have lower yields than our other investments and, accordingly, may result in lower distributions, if any, during such period. Our ability to achieve our investment objective may be limited to the extent that the net proceeds from an offering, pending full investment, are held in lower yielding interest-bearing deposits or other short-term instruments.

#### BUSINESS
The information contained under the caption "*Business*" in Part I. Item 1 of our most recent Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm#ia87130eb6a35479584dd555e26cc92d7_16) is incorporated by reference herein.

#### MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS
The information contained under the captions "*Management's Discussion and Analysis of Financial Condition and Results of Operations*" in Part II. Item 7 of our most recent Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm#ia87130eb6a35479584dd555e26cc92d7_46) and in Part I. Item 2 of our most recent Quarterly Report on [Form 10-Q](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174124000005/gain-20231231.htm#i1d8f1f06c7844f69bb1da9c01f33f3ee_118) are incorporated by reference herein.

#### PRICE RANGE OF COMMON STOCK
The information contained under the caption "*Market for Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities*" in Part II. Item 5 of our most recent Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm#ia87130eb6a35479584dd555e26cc92d7_37) is incorporated by reference herein.

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#### PORTFOLIO COMPANIES
The following table sets forth certain information as of December 31, 2023, regarding each portfolio company in which we had a debt or equity security as of such date. All such investments have been made in accordance with our investment objectives and strategies and our investment policies and procedures described in this prospectus. Under the 1940 Act, we may not acquire any non-qualifying assets unless, at the time such acquisition is made, qualifying assets represent at least 70% of our total assets. As of December 31, 2023, our investment in Funko Acquisition Holdings, LLC was considered a non-qualifying asset under Section 55 of the 1940 Act and represented less than 0.1% of total investments, at fair value.

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| | | | | | |
|:---|:---|:---|:---|:---|:---|
| **Company** | **Industry** | **Investment** | **Percentage of**<br>**Class Held**<br>**on a Fully**<br>**Diluted Basis** | **Cost** | **Fair**<br>**Value** |
|  |  |  | | **(Dollar amounts in**<br> **thousands)**<br> (unaudited) | **(Dollar amounts in**<br> **thousands)**<br> (unaudited) |
|  **NON-CONTROL/NON-AFFILIATE INVESTMENTS:** | **NON-CONTROL/NON-AFFILIATE INVESTMENTS:** | **NON-CONTROL/NON-AFFILIATE INVESTMENTS:** | **NON-CONTROL/NON-AFFILIATE INVESTMENTS:** | **NON-CONTROL/NON-AFFILIATE INVESTMENTS:** | **NON-CONTROL/NON-AFFILIATE INVESTMENTS:** |
|  Brunswick Bowling Products, Inc.<br> 525 West Laketon Ave.<br> Muskegon, MI 49441 | Home and Office Furnishings, Housewares, and Durable Consumer Products | Secured First Lien Term Debt |  | 17700 | 17700 |
|  |  | Secured First Lien Term Debt |  | 6850 | 6850 |
|  |  | Preferred Stock | 75.9% | 6653 | 43599 |
|  |  |  |  | 31203 | 68149 |
|  Dema/Mai Holdings, Inc.<br> 7384 S Alton Way, Suite 203<br> Centennial, CO 80112 | Building and Real Estate | Secured First Lien Term Debt |  | 38250 | 38250 |
|  |  | Preferred Stock | 45.5% | 21000 | 26102 |
|  |  |  |  | 59250 | 64352 |
|  Diligent Delivery Systems<br> 333 N. Sam Houston Parkway E., Suite 100<br> Houston, TX 77060 | Cargo Transport | Secured Second Lien Term Debt |  | 13000 | 13000 |
|  Diligent Delivery Systems<br> 333 N. Sam Houston Parkway E., Suite 100<br> Houston, TX 77060 |  | Common Stock Warrants | 8.0% | 500 | 500 |
|  |  |  |  | 13500 | 13500 |
|  Educators Resource, Inc.<br> 2575 Schillinger Rd. North<br> Semmes, AL 36575 | Healthcare, Education, and Childcare | Secured First Lien Term Debt |  | 20000 | 20000 |
|  Educators Resource, Inc.<br> 2575 Schillinger Rd. North<br> Semmes, AL 36575 |  | Preferred Stock | 55.0% | 8560 | 30237 |
|  |  |  |  | 28560 | 50237 |
|  The E3 Company, LLC<br> 301 Marvin A. Smith Rd.<br> Kilgore, TX 75662 | Oil and Gas | Secured First Lien Line of Credit |  | 1000 | 1000 |
|  |  | Secured First Lien Term Debt |  | 33750 | 33750 |
|  |  | Preferred Stock | 70.4% | 11233 | 11233 |
|  |  |  |  | 45983 | 45983 |
|  Funko Acquisition Holdings, LLC<br> 1202 Shuksan Way<br> Everett, WA 98203 | Personal and Non-Durable Consumer Products (Manufacturing Only) | Common Stock | 0.001% | 21 | 22 |
|  |  |  |  | 21 | 22 |

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|:---|:---|:---|:---|:---|:---|
|  Galaxy Technologies Holdings, Inc.<br> 1111 Industrial Rd.<br> Winfield, KS 67156 | Aerospace and Defense | Secured Second Lien Term Debt |  | 6900 | 6900 |
|  |  | Secured Second Lien Term Debt |  | 18796 | 18796 |
|  |  | Common Stock | 65.9% | 11513 | 58 |
|  |  |  |  | 37209 | 25754 |
|  Ginsey Home Solutions, Inc.<br> 2078 Center Square Rd.<br> Swedesboro, NJ 08085 | Home and Office Furnishings, Housewares, and Durable Consumer Products | Secured First Lien Term Debt |  | 12200 | 12153 |
|  |  | Preferred Stock | 94.9% | 9583 |  |
|  |  | Common Stock | 78.5% | 8 |  |
|  |  |  |  | 21791 | 12153 |
|  Home Concepts Acquisition, Inc.<br> 1378 Camino Rio Verde<br> Santa Barbara, CA 93111 | Printing and Publishing | Secured First Lien Line of Credit |  | 1500 | 1500 |
|  |  | Secured First Lien Term Debt |  | 12000 | 12000 |
|  |  | Preferred Stock | 47.6% | 3275 | 1710 |
|  |  |  |  | 16775 | 15210 |
|  Horizon Facilities Services, LLC<br> 5235 Oakview Dr.<br> Allentown, PA 18104 | Diversified/Conglomerate Service | Secured First Lien Term Debt |  | 57700 | 57700 |
|  |  | Preferred Stock | 55.8% |  | 5382 |
|  |  |  |  | 57700 | 63082 |
|  Mason West, LLC<br> 1601 E. Miraloma Ave<br> Placentia, CA 92870 | Diversified/Conglomerate Service | Secured First Lien Term Debt |  | 25250 | 25250 |
|  |  | Preferred Stock | 43.6% | 11206 | 20146 |
|  |  |  |  | 36456 | 45396 |
|  Nocturne Villa Rentals, Inc.<br> 28 Pelham St.<br> Newport, RI 02840 | Hotels, Motels, Inns and Gaming | Secured First Lien Line of Credit |  | 4000 | 4000 |
|  |  | Secured First Lien Term Debt |  | 61100 | 61100 |
|  |  | Preferred Stock | 53.6% | 6600 | 15457 |
|  |  |  |  | 71700 | 80557 |
|  Phoenix Door Systems, Inc.<br> 7390 Union Centre Blvd.<br> West Chester, OH 45014 | Diversified/Conglomerate Manufacturing | Secured First Lien Line of Credit |  | 2750 | 2750 |
|  |  | Secured First Lien Term Debt |  | 3200 | 2544 |
|  |  | Common Stock | 23.5% | 1830 |  |
|  |  |  |  | 7780 | 5294 |

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|:---|:---|:---|:---|:---|:---|
|  Schylling, Inc.<br> 21 High Street, Suite 400<br> North Andover, MA 01845 | Leisure, Amusement, Motion Pictures, and Entertainment | Secured First Lien Term Debt |  | 27981 | 27981 |
|  |  | Preferred Stock | 51.4% | 4000 | 10375 |
|  |  |  |  | 31981 | 38356 |
|  SFEG Holdings, Inc.<br> 4433 South Dr.<br> Houston, TX 77053 | Machinery (Non-agriculture, Non-construction, Nonelectronic) | Secured Second Lien Term Debt |  | 54644 | 54644 |
|  |  | Common Stock | 96.8% | 30746 | 37649 |
|  |  |  |  | 85390 | 92293 |
|  **Total Non-Control/Non-Affiliate Investments (represents 68.7% of total investments at fair value)** | **Total Non-Control/Non-Affiliate Investments (represents 68.7% of total investments at fair value)** | **Total Non-Control/Non-Affiliate Investments (represents 68.7% of total investments at fair value)** | **Total Non-Control/Non-Affiliate Investments (represents 68.7% of total investments at fair value)** | $**545299** | $**620338** |
|  **AFFILIATE INVESTMENTS:** | **AFFILIATE INVESTMENTS:** | **AFFILIATE INVESTMENTS:** | **AFFILIATE INVESTMENTS:** | **AFFILIATE INVESTMENTS:** | **AFFILIATE INVESTMENTS:** |
|  B+T Group Acquisition, Inc.<br> 1717 Boulder Ave #300<br> Tulsa, OK 74119 | Telecommunications | Secured First Lien Line of Credit |  | $2800 | $2800 |
|  |  | Secured First Lien Term Debt |  | 14000 | 6081 |
|  |  | Preferred Stock | 64.5% | 4722 |  |
|  |  | Common Stock Warrants | 3.5% |  |  |
|  |  |  |  | 21522 | 8881 |
|  ImageWorks Display and Marketing Group, Inc.<br> 415 Wachovia Street<br> Winston-Salem, NC 27101 | Diversified/Conglomerate Services | Secured First Lien Term Debt |  | 22000 | 22000 |
|  |  | Preferred Stock | 50.4% | 6749 | 1855 |
|  |  |  |  | 28749 | 23855 |
|  J.R. Hobbs Co.—Atlanta, LLC<br> 2021 Cedars Rd., Suite 100<br> Lawrenceville, GA 30043 | Diversified/Conglomerate Services | Secured First Lien Line of Credit |  | 5000 | 2670 |
|  |  | Secured First Lien Term Debt |  | 16500 | 8810 |
|  |  | Secured First Lien Term Debt |  | 26000 | 13882 |
|  |  | Secured First Lien Term Debt |  | 2438 | 1301 |
|  |  | Preferred Stock | 77.9% | 10920 |  |
|  |  |  |  | 60858 | 26663 |
|  The Maids International, LLC.<br> 9394 West Dodge Rd, Suite 140<br> Omaha, NE 68114 | Diversified/Conglomerate Services | Secured First Lien Term Debt |  | 28560 | 28560 |
|  |  | Preferred Stock | 70.8% | 6640 | 6392 |
|  |  |  |  | 35200 | 34952 |

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|:---|:---|:---|:---|:---|:---|
|  Nth Degree Investment Group, LLC<br> 3237 Satellite Blvd, Building 300, Suite 600<br> Duluth, GA 30096 | Diversified/Conglomerate Service | Secured Second Lien Term Debt |  | 25000 | 24884 |
|  |  | Common Stock | 14.0% | 6219 | 36309 |
|  |  |  |  | 31219 | 61193 |
|  Old World Christmas, Inc.<br> PO Box 8000<br> Spokane, WA 99203 | Home and Office Furnishings, Housewares, and Durable Consumer Products | Secured First Lien Term Debt |  | 43000 | 43000 |
|  |  | Preferred Stock | 82.8% |  | 32595 |
|  |  |  |  | 43000 | 75595 |
|  PSI Molded Plastic, Inc.<br> 5 Wickers Drive<br> Wolfeboro, NH 03894 | Chemicals, Plastics, and Rubber | Secured First Lien Term Debt |  | 26618 | 19256 |
|  |  | Preferred Stock | 70.1% | 19730 |  |
|  |  |  |  | 46348 | 19256 |
|  Utah Pacific Bridge & Steel, Ltd.<br> 50 North Geneva Rd.<br> Lindon, UT 84042 | Mining, Steel, Iron and Non-Precious Metals | Secured First Lien Term Debt |  | 18250 | 18250 |
|  |  | Preferred Stock | 67.5% | 6000 | 9581 |
|  |  |  |  | 24250 | 27831 |
|  **Total Affiliate Investments (represents 30.8% of total investments at fair value)** | **Total Affiliate Investments (represents 30.8% of total investments at fair value)** | **Total Affiliate Investments (represents 30.8% of total investments at fair value)** | **Total Affiliate Investments (represents 30.8% of total investments at fair value)** | $**291146** | $**278226** |
|  **CONTROL INVESTMENTS:** |  |  |  |  |  |
|  Edge Adhesives Holdings, Inc.<br> 3709 Grove City Rd.<br> Grove City, OH 43123 | Diversified/Conglomerate Manufacturing | Secured First Lien Term Debt |  | $9210 | $4244 |
|  |  | Preferred Stock | 37.7% | 8199 |  |
|  |  |  |  | 17409 | 4244 |
|  The Mountain Corporation<br> 59 Optical Ave.<br> Keene, NH 03431 | Personal and Non-Durable Consumer Products (Manufacturing Only) | Secured First Lien Line of Credit |  | 4550 |  |
|  |  | Secured Second Lien Term Debt |  | 3200 |  |
|  |  | Preferred Stock | 68.9% | 6899 |  |
|  |  | Common Stock | 77.2% | 1 |  |
|  |  |  |  | 14650 |  |
|  **Total Control Investments (represents 0.5% of total investments at fair value)** | **Total Control Investments (represents 0.5% of total investments at fair value)** | **Total Control Investments (represents 0.5% of total investments at fair value)** | **Total Control Investments (represents 0.5% of total investments at fair value)** | $**32059** | $**4244** |
|  **TOTAL INVESTMENTS** | **TOTAL INVESTMENTS** | **TOTAL INVESTMENTS** | **TOTAL INVESTMENTS** | $**868504** | $**902808** |

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#### Significant Portfolio Companies
Set forth below is a brief description of each portfolio company in which we have made an investment whose fair value represented greater than 5% of our total assets as of December 31, 2023. Because of the relative size of our investments in these companies, we are exposed to a greater degree to the risks associated with these companies.

#### Brunswick Bowling Products, Inc. ("Brunswick")
Our investments in Brunswick had an aggregate fair value of $68.1 million as of December 31, 2023, and included $6.7 million of preferred stock, at cost, and two secured first lien term loans with an aggregate principal amount outstanding of $24.6 million, which matures on January 23, 2026.

Founded in 1845, Brunswick, headquartered in Muskegon, Michigan, is a leader in the recreation industry and provides industry expertise, products, installation and maintenance for the development and renovation of new and existing bowling centers as well as mixed-use facilities across the entertainment industry.

Our Adviser has entered into a services agreement with Brunswick, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by Brunswick and our Adviser.

Because of the relative size of this investment, we are significantly exposed to the risks associated with Brunswick's business. Brunswick's business is dependent on the development and construction of new bowling and bowling-related venues, and a decline in the popularity of these venues would have a negative impact on Brunswick's financial performance. Additionally, the death, disability or departure by one or more of Brunswick's senior managers could have a negative impact on its business and operations.

One of the Adviser's managing directors, Christopher Lee, serves as a director of Brunswick's board. Brunswick's principal executive office is located at 525 West Laketon Ave., Muskegon, Michigan 49441.

#### Dema/Mai Holdings, Inc. ("Dema")
Our investments in Dema had an aggregate fair value of $64.4 million as of December 31, 2023, and included $21.0 million of preferred stock, at cost, and a secured first lien term loan with an aggregate principal amount outstanding of $38.3 million, which matures on July 1, 2027.

Dema is the largest provider of plumbing construction services to national homebuilders focused on single family houses in the Colorado Front Range. Dema is also a leading provider of mechanical contracting services to multi-family developers in the Denver metropolitan area.

Our Adviser has entered into a services agreement with Dema, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by Dema and our Adviser.

Because of the relative size of this investment, we are significantly exposed to the risks associated with Dema's business. Dema's business is dependent on continued housing development in Colorado's Front Range. Additionally, the death, disability or departure by one or more of Dema's senior managers could have a negative impact on its business and operations.

One of the Adviser's principals, Daniel Crump, serves as a director of Dema's board. Dema's principal executive office is located at 7384 S Alton Way, Centennial, Colorado 80112.

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#### Educators Resource, Inc. ("Educators Resource")
Our investments in Educators Resource had an aggregate fair value of $50.2 million as of December 31, 2023, and included $8.6 million of preferred stock, at cost, and a secured first lien term loan with a principal amount outstanding of $20.0 million, which matures on March 31, 2025.

Educators Resource is a leading wholesale distributor of school supplies and K-12 supplemental teaching materials to market leading e-retailers and brick-and-mortar stores nationwide. By supplying more than 20,000 educational SKUs, Educators Resource is a one-stop shop for school supplies for school districts, teachers, and parents nationwide.

Our Adviser has entered into a services agreement with Educators Resource, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by Educators Resource and our Adviser.

Because of the relative size of this investment, we are exposed to the risks associated with Educators Resource's business. Educators Resource's business is dependent on ample supply of educational products from its vendors and labor availability for fulfilling orders in the warehouse. Additionally, the death, disability or departure by one or more of Educators Resource's senior managers could have a negative impact on its business and operations.

One of the Adviser's managing directors, Erika Highland, serves as a director of Educators Resource's board. Educators Resource's principal executive office is located at 2575 Schillinger Rd N, Semmes, Alabama 36575.

#### Horizon Facilities Services, Inc. ("Horizon")
Our investments in Horizon had an aggregate fair value of $63.1 million as of December 31, 2023, and included preferred stock with zero cost basis, and a secured first lien term loan with an aggregate principal amount outstanding of $57.7 million, which matures on June 28, 2026.

Horizon is a leading provider of outsourced services to the rental car industry under the Managed Labor Solutions brand. Additionally, Horizon provides commercial janitorial services under the Professional Maintenance Co. brand. Horizon partners with its customers through a transaction-based pricing model which enhances customer cost visibility and operational efficiency.

Our Adviser has entered into a services agreement with Horizon, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by Horizon and our Adviser.

Because of the relative size of this investment, we are significantly exposed to the risks associated with Horizon's business. Horizon's business is dependent on the continued volume of cars rented, and the car rental industry is exposed to economic cycles as car rental expenditures are highly correlated with economic activity. Horizon has two large customers and the loss of either or both customers would have a significant impact on the company's financial performance. Additionally, the death, disability, or departure by one or more of Horizon's senior managers could have a negative impact on its business and operations.

One of the Adviser's managing directors, Christopher Lee, serves as a director of Horizon's board. Horizon's principal executive office is located at 5235 Oakview Drive, Allentown, Pennsylvania 18104.

#### Nocturne Luxury Villas, Inc. ("Nocturne")
Our investments in Nocturne had an aggregate fair value of $80.6 million as of December 31, 2023, and included $6.6 million of preferred stock, at cost, a secured first lien revolving line of credit with a principal

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amount outstanding of $4.0 million, which matures on June 2, 2024, and a secured first lien term loan with a principal amount outstanding of $61.1 million, which matures on June 3, 2026.

Nocturne isa platform built to acquire and manage leading villa rental management companies located throughout North America, with properties in the Caribbean, Telluride, Cabo San Lucas, Santa Barabara, and the 30A corridor of Florida's Gulf Coast. Across these five markets, Nocturne manages over 1,000 properties.

Our Adviser has entered into a services agreement with Nocturne, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by Nocturne and our Adviser.

Because of the relative size of this investment, we are exposed to the risks associated with Nocturne's business. Nocturne's business is dependent on continued activity in the domestic luxury travel market, which could be negatively impacted by travel shifting to Europe or a pronounced slowdown in the overall economy. Additionally, the death, disability or departure by one or more of Nocturne's senior managers could have a negative impact on its business and operations.

One of the Adviser's managing directors, Erika Highland, serves as a director of Nocturne's board. Nocturne's principal executive office is located at 28 Pelham St, Newport, Rhode Island 02840.

#### Nth Degree Investment Group, LLC ("Nth Degree")
Our investments in Nth Degree had an aggregate fair value of $61.2 million as of December 31, 2023, and included $6.2 million of common stock, at cost, and a secured second lien term loan with a principal amount outstanding of $25.0 million, which matures on June 28, 2029.

Founded in 1979, Nth Degree is a multifaceted face-to-face event marketing and management services organization. Nth Degree operates three divisions. The labor division provides installation and dismantle services for tradeshow exhibits across the country. Nth Degree is the largest exhibitor-appointed provider of this service in the U.S. The events division provides event management services for large corporate events, managing logistics, sales and sponsorship, education services, and all other facets of these events. The Fern Exposition Services division is a leading trade show service provider and general contractor.

Our Adviser has entered into a services agreement with Nth Degree, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by Nth Degree and our Adviser.

Because of the relative size of this investment, we are significantly exposed to the risks associated with Nth Degree's business. The tradeshow industry is exposed to economic cycles as tradeshow expenditures are highly correlated with economic activity. Nth Degree's events division has two large customers and the loss of either or both customers would have a significant impact on the company's financial performance, however, these customers do not represent a significant percentage of the company's overall revenue. Additionally, the death, disability, or departure by one or more of Nth Degree's senior managers could have a negative impact on its business and operations.

One of the Adviser's principals, Mitchell Grant, serves as a director of Nth Degree's board. Nth Degree's principal executive office is located at 3237 Satellite Boulevard Suite 600, Duluth, Georgia 30096.

#### Old World Christmas, Inc. ("Old World")
Our investments in Old World had an aggregate fair value of $75.6 million as of December 31, 2023, and included preferred stock with zero cost basis, and a secured first lien term loan with a principal amount outstanding of $43.0 million, which matures on December 17, 2025.

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Old World is a designer, manufacturer, and marketer of premium figural glass Christmas ornaments.

Our Adviser has entered into a services agreement with Old World, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by Old World and our Adviser.

Because of the relative size of this investment, we are exposed to the risks associated with Old World's business. Old World's business is largely dependent on sales in physical retail stores within the United States, and the continued decline of physical retail could have a negative impact on Old World's financial performance. Additionally, the death, disability or departure by one or more of Old World's senior managers could have a negative impact on its business and operations.

One of our Adviser's managing directors, Erika Highland, serves as a director of Old World's board. Old World's principal executive office is located at 4007 East Main Ave., Spokane, Washington 99202.

#### SFEG Holdings Inc. ("SFEG")
Our investments in SFEG had an aggregate fair value of $92.3 million as of December 31, 2023, and included $30.7 million of common stock, at cost, and a secured second lien term loan with an aggregate principal amount outstanding of $54.6 million, which matures on October 19, 2028.

SFE Group is an industry leading designer & provider of Specialized Fabrication, Machining & Welding equipment headquartered out of the global energy hub of Houston in the USA, but serving customers globally with a presence in 30+ countries through world class facilities and extended network of distributors and partners. SFE Group owns brands like Mathey Dearman, Climax, H&S Tools, Axxair & Magnatech, who are industry pioneers in the field of portable machine fabrication & welding. Utilized for high precision fabrication of critical industrial & infrastructure assets, SFE Group's best-in-class products & unrivaled engineering capabilities, enable mission-critical MRO and manufacturing jobs to be performed safer, faster & more cost effectively.

Our Adviser has entered into a services agreement with SFEG, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by SFEG and our Adviser.

Because of the relative size of this investment, we are significantly exposed to the risks associated with SFEG's business. SFEG's business serves the industrial markets, and so is dependent on the level of economic activity, particularly around the energy, construction, and general industrial markets. Additionally, the death, disability or departure by one or more of SFEG's senior managers could have a negative impact on its business and operations.

One of the Adviser's managing directors, Christopher Lee, serves as a director of SFEG's board. SFEG's principal executive office is located at 4433 South Dr. Houston, Texas 77053.

#### The E3 Company, LLC ("E3")
Our investments in E3 had an aggregate fair value of $46.0 million as of December 31, 2023, and included $11.2 million of preferred stock, at cost, a secured first lien revolving line of credit with a principal amount outstanding of $1.0 million, which matures on February 8, 2025, and a secured first lien term loan with a principal amount outstanding of $33.8 million, which matures on September 8, 2028.

E3 is focused on enhancing safety in the oilfield, which they do by designing, manufacturing, and servicing automated pressure management systems used by oil and gas companies in the well completion process. These patented systems increase safety in the oilfield by removing humans from the red zone, which is increasingly important to oil and gas companies.

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Our Adviser has entered into a services agreement with E3, pursuant to which our Adviser has agreed to advise and provide certain management and consulting services as mutually agreed upon by E3 and our Adviser.

Because of the relative size of this investment, we are significantly exposed to the risks associated with E3's business. E3 is dependent on the continued development of domestic oil and gas resources, as well as a continued focus by oil and gas companies on improving the safety of operating conditions in the oilfield. Additionally, the death, disability or departure by one or more of E3's senior managers could have a negative impact on its business and operations.

One of the Adviser's managing directors, Christopher Lee, serves as a director of E3's board. E3's principal executive office is located at 301 Marvin A. Smith Road, Kilgore, Texas 75662.

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#### MANAGEMENT
The information contained under the captions "*Proposal 1 — Election of Directors*," "*Information Regarding the Board of Directors and Corporate Governance — Director Independence*," "*Executive Compensation*," "*Director Compensation*" and "*Certain Transactions*" in our most recent [Definitive Proxy Statement](http://www.sec.gov/Archives/edgar/data/1321741/000119312523168511/d440993ddef14a.htm) with respect to an annual meeting of our stockholders incorporated by reference into Part III of our Annual Report on Form 10-K and "*Business*" in Part I. Item 1 of our most recent Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm#ia87130eb6a35479584dd555e26cc92d7_16) is incorporated by reference herein.

#### PORTFOLIO MANAGEMENT
We are externally managed by our Adviser, an affiliate of ours, under an investment advisory agreement between us and the Adviser (the "Advisory Agreement") and another of our affiliates, the Administrator, provides administrative services to us pursuant to an administrative agreement (the "Administration Agreement"). Each of the Adviser and Administrator is a privately held company that is currently indirectly owned and controlled by David Gladstone, our chairman and chief executive officer. Mr. Gladstone and Terry Lee Brubaker, our chief operating officer, also serve on the board of directors of the Adviser, the board of managers of the Administrator, and serve as executive officers of the Adviser and the Administrator. Our Adviser directly employs personnel that manage our portfolio investments and directly pays our payroll, benefits and general expenses regarding such personnel. The Administrator employs, among others, our chief financial officer and treasurer, chief valuation officer, chief compliance officer, general counsel and secretary (who also serves as the president of the Administrator) and their respective staffs. In addition to the fees payable under the Advisory Agreement and the Administration Agreement (as described below), we pay our direct expenses, including directors' fees, legal and accounting fees and stockholder related expenses. The Adviser and Administrator have extensive experience in our lines of business and also provide investment advisory and administrative services, respectively, to our affiliates, including the Affiliated Public Funds. In the future, the Adviser and Administrator may provide investment advisory and administrative services, respectively, to other funds and companies, both public and private.

The principal executive office of the Adviser and Administrator is 1521 Westbranch Drive, Suite 100, McLean, Virginia 22102.

*Management Services Provided to Us by our Adviser* 

Our Adviser is a Delaware corporation registered as an investment adviser under the Advisers Act. Subject to the overall supervision of our Board of Directors, our Adviser provides investment advisory and management services to us. Under the terms of our Advisory Agreement, our Adviser has investment discretion with respect to our capital and, in that regard:

• determines the composition of our portfolio, the nature and timing of the changes to our portfolio, and the manner of implementing such changes;

• identifies, evaluates, and negotiates the structure of the investments we make (including performing due diligence on our prospective portfolio companies);

• closes and monitors the investments we make; and

• makes available on our behalf, and provides if requested, managerial assistance to our portfolio companies.

Our Adviser's services under the Advisory Agreement are not exclusive, and it is free to furnish similar services to other entities, provided that its services to us are not impaired.

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*Portfolio Management* 

Our Adviser takes a team approach to portfolio management; however, the following persons are primarily responsible for the day-to-day management of our portfolio: David Gladstone, Terry Lee Brubaker and David Dullum, whom we refer to collectively as the Portfolio Managers. In addition, our Adviser has an investment committee that evaluates and approves each of our investments. This investment committee is currently comprised of Messrs. Gladstone, Brubaker, and Dullum, along with Mr. John Sateri, who is a managing director of our Adviser; and Ms. Laura Gladstone, who is a managing director of our Adviser. Our investment decisions are made on our behalf by the investment committee of our Adviser upon approval of at least 75% of the investment committee.

Mr. Gladstone has served as the chairman and the chief executive officer of the Adviser, since he founded the Adviser in 2002, along with Mr. Brubaker. Mr. Brubaker has served as the vice chairman and chief operating officer of the Adviser since 2002 and served as secretary of the Adviser from 2002 to February 2011. Mr. Dullum has served as an executive managing director of the Adviser since 2008. Mr. Sateri has been a managing director of our Adviser since 2007. Ms. Gladstone has been a managing director of our Adviser since 2001. Ms. Gladstone and Mr. Sateri each have over 20 years of experience in investing in middle market companies and continue to hold the role of managing director with the Company and the Adviser. For more complete biographical information on Messrs. Gladstone, Brubaker and Dullum, see "Proposal 1 — Election of Directors" in our most recent Definitive Proxy Statement for our Annual Meeting of Stockholders which is incorporated by reference herein.

As discussed above, the Portfolio Managers are all officers or directors, or both, of our Adviser, and Messrs. Gladstone and Brubaker are managers of the Administrator. Mr. Gladstone is also the sole stockholder of the parent company of the Adviser and the Administrator. Although we believe that the terms of the Advisory Agreement and the Administration Agreement are no less favorable to us than those that could be obtained from unaffiliated third parties in arms' length transactions, our Adviser and Administrator and their officers and directors have a material interest in the terms of these agreement.

Our Adviser and Administrator provide investment advisory and administration services, respectively, to the other Affiliated Public Funds. As such, certain of our Portfolio Managers also are primarily responsible for the day-to-day management of the portfolios of other pooled investment vehicles in the Affiliated Public Funds that are managed by the Adviser. As of the date hereof, Messrs. Gladstone, Brubaker and Robert Marcotte (the president of Gladstone Capital and an executive managing director of the Adviser) are primarily responsible for the day-to-day management of the portfolio of Gladstone Capital, another publicly-traded BDC; Messrs. Gladstone, Brubaker and Arthur Cooper (the president of Gladstone Commercial and an executive managing director of the Adviser) are primarily responsible for the day-to-day management of Gladstone Commercial, a publicly-traded real estate investment trust; and Messrs. Gladstone and Brubaker are primarily responsible for the day-to-day management of Gladstone Land, a publicly traded real estate investment trust. As of December 31, 2023, the Adviser had an aggregate of approximately $4.2 billion in total assets under management in the Company and the Affiliated Public Funds, all of which is subject to performance-based advisory fees and for which Messrs. Gladstone and Brubaker are primarily responsible for the day-to-day management.

*Conflicts of Interest* 

As discussed above, the Portfolio Managers who are our executive officers and directors, and the officers and directors of the Adviser, serve or may serve as officers, directors, or principals of entities that operate in the same or a related line of business as we do or of investment funds managed by our affiliates. Accordingly, they may have obligations to investors in those entities, the fulfillment of which might not be in the best interests of us or our stockholders. For example, Mr. Gladstone, our chairman and chief executive officer, is chairman of the board and chief executive officer of the Adviser, the Administrator and the Affiliated Public Funds. In addition, Mr. Brubaker, our chief operating officer, is vice chairman and chief operating officer of the Adviser, the

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Administrator and the Affiliated Public Funds. Mr. Dullum, our president, is an executive managing director of the Adviser. Moreover, the Adviser may establish or sponsor other investment vehicles which from time to time may have potentially overlapping investment objectives with ours and accordingly may invest in, whether principally or secondarily, asset classes we target. While the Adviser generally has broad authority to make investments on behalf of the investment vehicles that it advises, the Adviser has adopted investment allocation procedures to address these potential conflicts and intends to direct investment opportunities to the Company or the Affiliated Public Fund with the investment strategy that most closely fits the investment opportunity. Nevertheless, the management of the Adviser may face conflicts in the allocation of investment opportunities to other entities managed by the Adviser. As a result, it is possible that we may not be given the opportunity to participate in certain investments made by other funds managed by the Adviser.

In certain circumstances, we may make investments in a portfolio company in which one of our affiliates has or will have an investment, subject to satisfaction of any regulatory restrictions and, where required, the prior approval of our Board of Directors. As of December 31, 2023, our Board of Directors has approved the following types of transactions:

• Our affiliate, Gladstone Commercial, may, under certain circumstances, lease property to portfolio companies that we do not control. We may pursue such transactions only if (i) the portfolio company is not controlled by us or any of our affiliates, (ii) the portfolio company satisfies the tenant underwriting criteria of Gladstone Commercial, and (iii) the transaction is approved by a majority of our independent directors and a majority of the independent directors of Gladstone Commercial. We expect that any such negotiations between Gladstone Commercial and our portfolio companies would result in lease terms consistent with the terms that the portfolio companies would be likely to receive were they not portfolio companies of ours.

• We may invest simultaneously with our affiliate Gladstone Capital in senior loans in the broadly syndicated market whereby neither we nor any affiliate has the ability to dictate the terms of the loans.

• Pursuant to the Co-Investment Order, under certain circumstances, we may co-invest with Gladstone Capital and any future BDC or closed-end management investment company that is advised by the Adviser (or sub-advised by the Adviser if it controls the fund) or any combination of the foregoing subject to the conditions included therein.

Certain of our officers, who are also officers of the Adviser, may from time to time serve as directors of certain of our portfolio companies. If an officer serves in such capacity with one of our portfolio companies, such officer will owe fiduciary duties to stockholders of the portfolio company, which duties may from time to time conflict with the interests of our stockholders.

In the course of our investing activities, we will pay management and incentive fees to the Adviser and will reimburse the Administrator for certain expenses it incurs. As a result, investors in our common stock will invest on a "gross" basis and receive distributions on a "net" basis after expenses, resulting in a lower rate of return than one might achieve through our investors themselves making direct investments. As a result of this arrangement, there may be times when the management team of the Adviser has interests that differ from those of our stockholders, giving rise to a conflict. In addition, as a BDC, we make available significant managerial assistance to our portfolio companies and provide other services to such portfolio companies. While neither we nor the Adviser currently receive fees in connection with managerial assistance, the Adviser and Gladstone Securities have, at various times, provided other services to certain of our portfolio companies and received fees for services other than managerial assistance as discussed in "*Business — Ongoing Management of Investments and Portfolio Company Relationships — Managerial Assistance and Services"* in Part I, Item 1 of our most recent Annual Report on Form 10-K.

*Portfolio Manager Compensation* 

The Portfolio Managers receive compensation from our Adviser in the form of a base salary plus a bonus. Each Portfolio Manager's base salary is determined by a review of salary surveys for persons with comparable

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experience who are serving in comparable capacities in the industry. Each Portfolio Manager's base salary is set and reviewed yearly. Like all employees of the Adviser, a Portfolio Manager's bonus is tied to the post-tax performance of the Adviser and the entities that it advises. A Portfolio Manager's bonus increases or decreases when the Adviser's income increases or decreases. The Adviser's income, in turn, is directly tied to the management and incentive fees earned in managing its investment funds, including Gladstone Investment. Pursuant to the Advisory Agreement, the Adviser receives a base management fee and an incentive fee based on net investment income in excess of the hurdle rates and capital gains as set out in the Advisory Agreement. During the fiscal years ended March 31, 2023, 2022 and 2021, we incurred net fees of approximately $20.2 million, $21.0 million and $17.9 million, respectively, to our Adviser under the Advisory Agreement. See "*Business — Transactions with Related Parties – Investment Advisory and Management Agreement*" in Part I, Item 1 of our most recent Annual Report on Form 10-K for a full discussion of how such fees are computed and paid. A discussion regarding the basis for the Board of Directors approving the Advisory Agreement is available in our Annual Report on Form 10-K for the fiscal year ended March 31, 2023.

*Portfolio Manager Beneficial Ownership* 

The following table sets forth, as of December 31, 2023, the dollar range of equity securities that are beneficially owned by each of our Portfolio Managers.

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| | |
|:---|:---|
| **Name** | **Dollar Range of Equity Securities of<br>the Company Owned by<br>Directors(1)(2)** |
|  David Gladstone | Over $1,000,000 |
|  Terry Lee Brubaker | Over $1,000,000 |
|  David A.R. Dullum | Over $1,000,000 |

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(1) Ownership is calculated in accordance with Rule 16-1(a)(2) of the Exchange Act.

(2) The dollar range of equity securities beneficially owned is calculated by multiplying the closing price of the respective class as reported on Nasdaq as of December 31, 2023, times the number of shares of the respective class so beneficially owned and aggregated accordingly.

#### CONTROL PERSONS AND PRINCIPAL STOCKHOLDERS
The information contained under the captions "*Security Ownership of Certain Beneficial Owners and Management*" in our most recent [Definitive Proxy Statement](http://www.sec.gov/Archives/edgar/data/1321741/000119312523168511/d440993ddef14a.htm) with respect to an annual meeting of our stockholders incorporated by reference into Part III of our Annual Report on Form 10-K is incorporated by reference herein.

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#### DIVIDEND REINVESTMENT PLAN
Our transfer agency and services agreement with our transfer agent, Computershare, Inc. ("Computershare"), authorizes Computershare to provide a dividend reinvestment plan that allows for reinvestment of our distributions on behalf of our common stockholders upon their election as provided below. As a result, if our Board of Directors authorizes, and we declare, a cash dividend, then our common stockholders who have "opted in" to the dividend reinvestment plan will not receive cash dividends but, instead, such cash dividends will automatically be reinvested in additional shares of our common stock.

Pursuant to the dividend reinvestment plan, if your shares of our common stock are registered in your own name you can have all distributions reinvested in additional shares of our common stock by Computershare, as the plan agent, if you enroll in the dividend reinvestment plan by delivering an enrollment form to the plan agent prior to the corresponding dividend record date, available at *www.computershare.com/investor*. The plan agent will effect purchases of our common stock under the dividend reinvestment plan in the open market.

If you do not elect to participate in the dividend reinvestment plan, you will receive all distributions in cash paid by check mailed directly to you (or if you hold your shares in street or other nominee name, then to your nominee) as of the relevant record date, by the plan agent, as our distribution disbursing agent. If your shares are held in the name of a broker or nominee, you can transfer the shares into your own name and then enroll in the dividend reinvestment plan or contact your broker or nominee to determine if they offer a dividend reinvestment plan.

The plan agent serves as agent for the holders of our common stock in administering the dividend reinvestment plan. After we declare a dividend, the plan agent will, as agent for the participants, receive the cash payment and use it to buy common stock on Nasdaq or elsewhere for the participants' accounts. The price of the shares will be the weighted average price of all shares purchased by the plan agent on such trade date or dates.

Stockholders can obtain additional information about, and participants in the dividend reinvestment plan may withdraw from, the dividend reinvestment plan at any time by contacting Computershare online at *www.computershare.com/investor*, via telephone at (781) 575-2000 or by mailing a request to 150 Royall Street, Canton, Massachusetts 02021 or by selling or transferring all applicable shares. If the plan agent receives a request to withdraw near a dividend record date, the plan agent, in its sole discretion, may either distribute such dividends in cash or reinvest the shares on behalf of the withdrawing participant. If such dividends are reinvested, the plan agent will process the withdrawal as soon as practicable, but in no event later than five business days after the reinvestment is completed.

The plan agent will maintain each participant's account in the dividend reinvestment plan and will furnish periodic written confirmations of all transactions in such account, including information needed by the stockholder for personal and tax records. Common stock in the account of each dividend reinvestment plan participant will be held by the plan agent in non-certificated form in the name of such participant; however participants may request that such shares be certificated in their name. The plan agent will provide proxy materials relating to our stockholders' meetings that will include those shares purchased through the plan agent, as well as shares held pursuant to the dividend reinvestment plan.

We pay the plan agent's fees for the handling or reinvestment of dividends and other distributions. If a participant elects by written notice to the plan agent prior to termination of his or her account to have the plan agent sell part or all of the shares held by the plan agent in the participant's account and remit the proceeds to the participant, the plan agent is authorized to deduct a transaction fee of $15.00 for each batch order sale and $25.00 for each market order, day limit order and good-til-canceled limit order sale, plus brokerage commissions of $0.10 per share, from the proceeds. The participants in the dividend reinvestment plan will also bear a transaction fee of up to $5.00, plus per share brokerage commissions of $0.10, incurred with respect to open market purchases.

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Distributions are taxable whether paid in cash or reinvested in additional shares, and the reinvestment of distributions pursuant to the dividend reinvestment plan will not relieve participants of any U.S. federal income tax or state income tax that may be payable or required to be withheld on such distributions. For more information regarding taxes that our stockholders may be required to pay, see "*Material U.S. Federal Income Tax Considerations.*"

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#### MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS
This is a general summary of certain material U.S. federal income tax considerations applicable to us, to our qualification and taxation as a RIC for U.S. federal income tax purposes under Subchapter M of the Code and to the ownership and disposition of our common stock. This discussion applies only to beneficial owners that acquired our shares in an initial offering.

This summary does not purport to be a complete description of all the income tax considerations applicable to an investment in our common stock. In particular, we have not described certain considerations that may be relevant to certain types of stockholders subject to special treatment under U.S. federal income tax laws, including stockholders subject to the alternative minimum tax, tax-exempt organizations, insurance companies, dealers in securities, a trader in securities that elects to use a mark-to-market method of accounting for its securities holdings, pension plans and trusts, financial institutions, real estate investment trusts, RICs, banks and other financial institutions, stockholders that are treated as partnerships for U.S. federal income tax purposes, U.S. persons whose functional currency is not the U.S. dollar, non-U.S. stockholders (as defined below) engaged in a trade or business in the United States or entitled to claim the benefits of an applicable income tax treaty, persons who have ceased to be U.S. citizens or to be taxed as residents of the United States, "controlled foreign corporations," "passive foreign investment companies" and persons that will hold our common stock as a position in a "straddle," "hedge" or as part of a "constructive sale" for U.S. federal income tax purposes or to the owners or partners of a stockholder. If we issue preferred stock that may be convertible into or exercisable or exchangeable for securities or other property or preferred stock with other terms that may have different U.S. federal income tax consequences than those described in this summary, the U.S. federal income tax consequences of that preferred stock will be described in the relevant prospectus supplement. This summary assumes that investors hold our common stock as capital assets (within the meaning of the Code). The discussion is based upon the Code, its legislative history, existing and proposed U.S. Treasury regulations and published rulings and court decisions all as currently in effect, all of which are subject to change or differing interpretations, possibly retroactively, which could affect the continuing validity of this discussion. We have not sought, and do not expect to seek, any ruling from the Internal Revenue Service ("IRS") regarding any matter discussed herein, and this discussion is not binding on the IRS. Accordingly, there can be no assurance that the IRS will not assert, and a court will not sustain, a position contrary to any of the tax consequences discussed herein.

This summary does not discuss any aspect of state, local or foreign tax laws, or the U.S. estate or gift tax. It does not discuss the special treatment under U.S. federal income tax laws that could result if we invest in tax-exempt securities or certain other investment assets. For purposes of this discussion, a "U.S. stockholder" is a beneficial owner of our common stock who is for U.S. federal income tax purposes:

• an individual who is a citizen or resident of the United States;

• a corporation, or other entity treated as a corporation for U.S. federal income tax purposes, created or organized in or under the laws of the United States or any state thereof or the District of Columbia;

• a trust, if a court within the United States has primary supervision over its administration and one or more U.S. persons (as defined in the Code) have the authority to control all of its substantial decisions, or if the trust has a valid election in effect under applicable U.S. Treasury regulations to be treated as a domestic trust for U.S. federal income tax purposes; or

• an estate, the income of which is subject to U.S. federal income taxation regardless of its source.

For purposes of this discussion, a "non-U.S. stockholder" is a beneficial owner of our common stock that is not a U.S. stockholder.

**An investment in shares is complex, and certain aspects of the U.S. tax treatment of such investment are not certain.** Tax matters are complicated, and the tax consequences of an investment in our common stock will depend on the facts of a stockholder's particular situation. Holders of our common stock are strongly

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encouraged to consult their tax advisor regarding the U.S. federal income tax consequences of the acquisition, ownership and disposition of our common stock, as well as the effect of state, local and foreign tax laws, and the effect of any possible changes in tax laws.

#### RIC Status
The information contained under the subheadings "*RIC Status*", "*Failure to Qualify as a RIC*" and "*Qualification as a RIC*" under the caption "*Material U.S. Federal Income Tax Considerations*" in Part I. Item 1 of our most recent Annual Report on Form 10-K is incorporated by reference herein.

#### Our Investments — General
Certain of our investment practices may be subject to special and complex U.S. federal income tax provisions that may, among other things, (1) treat dividends that would otherwise constitute qualified dividend income as non-qualified dividend income, (2) disallow, suspend or otherwise limit the allowance of certain losses or deductions, (3) convert lower-taxed long-term capital gain into higher-taxed short-term capital gain or ordinary income, (4) convert an ordinary loss or a deduction into a capital loss (the deductibility of which is more limited), (5) cause us to recognize income or gain without receipt of a corresponding cash payment, (6) adversely affect the time as to when a purchase or sale of stock or securities is deemed to occur, (7) adversely alter the characterization of certain complex financial transactions and (8) produce income that will not be qualifying income for purposes of the 90% Gross Income Test. We intend to monitor our transactions and may make certain tax elections in order to mitigate the effects of these provisions; however, no assurances can be given that we will be eligible for any of those tax elections or that any elections we make will fully mitigate the effects of these provisions.

Gain or loss recognized by us from securities and other financial assets acquired by us, as well as any loss attributable to the lapse of options, warrants, or other financial assets taxed as options, generally will be treated as capital gain or loss. The gain or loss generally will be long-term or short-term depending on how long we held a particular security or other financial asset. However, gain on the lapse of an option issued by us will be treated as short-term capital gain.

A portfolio company in which we invest may face financial difficulties that require us to work-out, modify or otherwise restructure our investment in the portfolio company. Any such transaction could, depending upon the specific terms of the transaction, cause us to recognize taxable income without a corresponding receipt of cash, which could affect our ability to satisfy the Annual Distribution Requirement or the Excise Tax Distribution Requirements or result in unusable capital losses and future non-cash income. Any such transaction could also result in us receiving assets that give rise to non-qualifying income for purposes of the 90% Gross Income Test.

Our investment in non-U.S. securities may be subject to non-U.S. income, withholding and other taxes. Stockholders generally will not be entitled to claim a U.S. foreign tax credit or deduction with respect to non-U.S. taxes paid by us.

If we purchase shares in a "passive foreign investment company" (a "PFIC"), we may be subject to U.S. federal income tax on a portion of any "excess distribution" received on, or any gain from the disposition of, such shares even if we distribute that income as a taxable dividend to the holders of our common stock. Additional charges in the nature of interest generally will be imposed on us in respect of deferred taxes arising from any such excess distribution or gain. If we invest in a PFIC and elect to treat the PFIC as a "qualified electing fund" under the Code (a "QEF"), in lieu of the foregoing requirements, we will be required to include in income each year our proportionate share of the ordinary earnings and net capital gain of the QEF, even if that income is not distributed by the QEF. Any required inclusions from the QEF election will be considered "good income" for purposes of the 90% Gross Income Test. Alternatively, we may be able to elect to mark-to-market at

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the end of each taxable year our shares in a PFIC; in this case, we will recognize as ordinary income any increase in the value of those shares, and as ordinary loss any decrease in such value to the extent that any such decrease does not exceed prior increases included in our income. Our ability to make either election will depend on factors beyond our control, and is subject to restrictions which may limit the availability of the benefit of these elections. Under either election, we may be required to recognize in a year income in excess of any distributions we receive from PFICs and any proceeds from dispositions of PFIC stock during that year, and that income will nevertheless be subject to the Annual Distribution Requirement and will be taken into account for purposes of determining whether we satisfy the Excise Tax Distribution Requirements. See "*— Taxation as a Regulated Investment Company*" above.

Our functional currency is the U.S. dollar for U.S. federal income tax purposes. Under Section 988 of the Code, gains or losses attributable to fluctuations in exchange rates between the time we accrue income, expenses or other liabilities denominated in a currency other than the U.S. dollar and the time we actually collect that income or pay that expense or liability are generally treated as ordinary income or loss. Similarly, gains or losses on foreign currency forward contracts, the disposition of debt denominated in a foreign currency, and other financial transactions denominated in a foreign currency, to the extent attributable to fluctuations in exchange rates between the acquisition and disposition dates, are also treated as ordinary income or loss.

#### Taxation of U.S. Stockholders
The following discussion applies only to U.S. stockholders. If you are not a U.S. stockholder, this section does not apply to you. U.S. stockholders who have elected to participate in our dividend reinvestment plan will have their cash dividends and distributions automatically reinvested in additional shares of our common stock, rather than receiving cash dividends and distributions. Any dividends or distributions reinvested under the plan will nevertheless remain taxable to U.S. stockholders. A U.S. stockholder will have an adjusted basis in the additional common stock purchased through the plan equal to the dollar amount that would have been received if the U.S. stockholder had received the dividend or distribution in cash, unless we were to issue new shares that are trading at or above net asset value ("NAV"), in which case, the U.S. stockholder's basis in the new shares would generally be equal to their fair market value. The additional shares will have a new holding period commencing on the day following the day on which the shares are credited to the U.S. stockholder's account.

*Distributions* 

For any period during which we qualify as a RIC for U.S. federal income tax purposes, distributions to our stockholders attributable to our Investment Company Taxable Income generally will be taxable as ordinary income to our stockholders to the extent of our current or accumulated earnings and profits. We first allocate our earnings and profits to distributions to our preferred stockholders, if any, and then to distributions to our common stockholders based on priority in our capital structure. Any distributions in excess of our earnings and profits will first be treated as a return of capital to the extent of the stockholder's adjusted basis in his or her shares of stock and thereafter as capital gain. Distributions of our long-term capital gains, reported by us as such, will be taxable to our stockholders as long-term capital gains regardless of the stockholder's holding period of the stock and whether the distributions are paid in cash or invested in additional stock. Corporate U.S. stockholders generally are eligible for the 50% dividends received deduction with respect to ordinary income dividends received from us, but only to the extent such amount is attributable to dividends received by us from taxable domestic corporations.

A RIC that has two or more classes of stock generally is required to allocate to each class proportionate amounts of each type of its income (such as ordinary income, capital gains, qualified dividend income and dividends qualifying for the dividends-received deduction) based upon the percentage of total distributions paid to each class for the tax year. Accordingly, for any tax year in which we have common shares and preferred shares, we intend to allocate capital gain distributions, distributions of qualified dividend income, and distributions qualifying for the dividends-received deduction, if any, between our common shares and preferred shares in proportion to the total distributions paid to each class with respect to such tax year.

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Any distribution declared by us in October, November or December of any calendar year, payable to our stockholders of record on a specified date in such a month and actually paid during January of the following year, will be treated as if it were paid by us and received by our stockholders on December 31 of the previous year. In addition, we may elect (in accordance with Section 855(a) of the Code) to relate a distribution back to the prior taxable year if we (1) declare such distribution prior to the later of the extended due date for filing our return for that taxable year or the 15th day of the ninth month following the close of the taxable year, (2) make the election in that return, and (3) distribute the amount in the 12-month period following the close of the taxable year but not later than the first regular distribution payment of the same type following the declaration. Any such election will not alter the general rule that a stockholder will be treated as receiving a distribution in the taxable year in which the distribution is made, subject to the October, November, December rule described above.

If a common stockholder participates in our "opt in" dividend reinvestment plan, then the common stockholder will have their cash dividends and distributions automatically reinvested in additional shares of our common stock, rather than receiving cash dividends and distributions. Any distributions reinvested under the plan will be taxable to the common stockholder to the same extent, and with the same character, as if the common stockholder had received the distribution in cash. The common stockholder will have an adjusted basis in the additional common shares purchased through the plan equal to the dollar amount that would have been received if the U.S. stockholder had received the dividend or distribution in cash, unless we were to issue new shares that are trading at or above net asset value, in which case, the U.S. stockholder's basis in the new shares would generally be equal to their fair market value. The additional common shares will have a new holding period commencing on the day following the day on which the shares are credited to the common stockholder's account. The plan agent purchases shares in the open market in connection with the obligations under the plan.

We expect to be treated as a "publicly offered regulated investment company." As a "publicly offered regulated investment company," in addition to our dividend reinvestment plan, we may choose to pay a majority of a required dividend in stock rather than cash. In order for the distribution to qualify for the Annual Distribution Requirement, the dividend must be payable at the election of each shareholder in cash or common stock (or a combination of the two), but may have a "cash cap" that limits the total amount of cash paid to not less than 20% of the entire distribution. If shareholders in the aggregate elect to receive an amount of cash greater than our cash cap, then each shareholder who elected to receive cash will receive a pro rata share of the cash and the rest of their distribution in our stock. The value of the portion of the distribution made in common stock will be equal to the amount of cash for which the common stock is substituted, and U.S. stockholders will be subject to tax on those amount as though they had received cash.

We may elect to retain our net capital gain or a portion thereof for investment and be taxed at corporate-level tax rates on the amount retained, and therefore designate the retained amount as a "deemed dividend." In this case, we may report the retained amount as undistributed capital gains to our U.S. stockholders, who will be treated as if each U.S. stockholder received a distribution of its pro rata share of this gain, with the result that each U.S. stockholder will (i) be required to report its pro rata share of this gain on its tax return as long-term capital gain, (ii) receive a refundable tax credit for its pro rata share of tax paid by us on the gain and (iii) increase the tax basis for its shares of common stock by an amount equal to the deemed distribution less the tax credit. In order to utilize the deemed distribution approach, we must provide written notice to our stockholders prior to the expiration of 60 days after the close of the relevant taxable year. We cannot treat any of our investment company taxable income as a "deemed distribution."

If a U.S. stockholder purchases shares of our common stock shortly before the record date of a distribution, the price of the shares will include the value of the distribution and the U.S. stockholder will be subject to tax on the distribution even though it economically represents a return of investment.

*Sale of Our Shares* 

A U.S. stockholder generally will recognize taxable gain or loss if the U.S. stockholder sells or otherwise disposes of the shares of our common stock. Any gain arising from such sale or disposition generally will be

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treated as long-term capital gain or loss if the U.S. stockholder has held the shares for more than one year. Otherwise, it will be classified as short-term capital gain or loss. However, any capital loss arising from the sale or disposition of shares of our stock held for six months or less will be treated as long-term capital loss to the extent of the amount of capital gain dividends received, or undistributed capital gain deemed received, with respect to such shares. All or a portion of any loss realized upon a taxable disposition of shares will be disallowed under the Code's "wash sale" rule if other substantially identical shares are purchased within 30 days before or after the disposition. In such a case, the basis of the newly purchased shares will be adjusted to reflect the disallowed loss. Under the tax laws in effect as of the date of this filing, individual U.S. stockholders are subject to a maximum federal income tax rate of 20% on their net capital gain (i.e. the excess of realized net long-term capital gain over realized net short-term capital loss for a taxable year) including any long-term capital gain derived from an investment in our shares. Such rate is lower than the maximum rate on ordinary income currently payable by individuals. Corporate U.S. stockholders currently are subject to federal income tax on net capital gain at the same rates applied to their ordinary income. Capital losses are subject to limitations on use for both corporate and non-corporate stockholders. Certain U.S. stockholders who are individuals, estates or trusts generally are also subject to a 3.8% Medicare tax on, among other things, dividends on and capital gain from the sale or other disposition of shares of our stock.

We will send to each of our U.S. stockholders, after the end of each calendar year, a notice providing, on a per share and per distribution basis, the amounts includible in the U.S. stockholder's taxable income for the applicable year as ordinary income and as long-term capital gain. In addition, the U.S. federal tax status of each year's distributions generally will be reported to the IRS (including the amount of dividends, if any, eligible for the preferential rates applicable to long-term capital gains).

Dividends paid by us generally will not be eligible for the dividends-received deduction or the preferential tax rate applicable to Qualifying Dividends because our income generally will not consist of dividends. Distributions by us out of current or accumulated earnings and profits also generally will not be eligible for the 20% pass through deduction under Section 199A of the Code, although under recently proposed regulations, qualified real estate investment trust dividends earned by us may qualify for the deduction under Section 199A of the Code. Distributions may also be subject to additional state, local and non-U.S. taxes depending on a U.S. stockholder's particular situation.

*Tax Shelter Reporting Regulations* 

If a U.S. stockholder recognizes a loss with respect to our common stock in excess of $2 million or more for a non-corporate U.S. stockholder or $10 million or more for a corporate U.S. stockholder in any single taxable year, the U.S. stockholder must file with the IRS a disclosure statement on Form 8886. Direct investors of portfolio securities in many cases are excepted from this reporting requirement, but under current guidance, equity owners of a RIC are not excepted. The fact that a loss is reportable under these regulations does not affect the legal determination of whether the taxpayer's treatment of the loss is proper. Significant monetary penalties apply to a failure to comply with this reporting requirement. States may also have similar reporting requirements. Shareholders are urged to consult their tax advisor to determine the applicability of these regulations in light of their individual circumstances.

#### Taxation of non-U.S. stockholders
The following discussion applies only to persons that are non-U.S. stockholders. If you are not a non-U.S. stockholder, this section does not apply to you. Whether an investment in shares of our common stock is appropriate for a non-U.S. stockholder will depend upon that person's particular circumstances. An investment in shares of our common stock by a non-U.S. stockholder may have adverse tax consequences and, accordingly, may not be appropriate for a non-U.S. stockholder. Non-U.S. stockholders are urged to consult their tax advisors before investing in our common stock.

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*Distributions* 

Distributions by us to non-U.S. stockholders generally will be subject to U.S. withholding tax (unless lowered or eliminated by an applicable income tax treaty) to the extent payable from our current or accumulated earnings and profits unless an exception applies.

If a non-U.S. stockholder receives distributions and those distributions are effectively connected with a U.S. trade or business of the non-U.S. stockholder and, if an income tax treaty applies, attributable to a permanent establishment in the United States of that non-U.S. stockholder, those distributions generally will be subject to U.S. federal income tax at the rates applicable to U.S. persons. In that case, we will not be required to withhold U.S. federal income tax if the non-U.S. stockholder complies with applicable certification and disclosure requirements.

Actual or deemed distributions of our net capital gain to a non-U.S. stockholder, and gains recognized by a non-U.S. stockholder upon the sale of our common stock, will not be subject to withholding of U.S. federal income tax and generally will not be subject to U.S. federal income tax unless (a) the distributions or gains, as the case may be, are effectively connected with a U.S. trade or business of the non-U.S. stockholder and, if an income tax treaty applies, are attributable to a permanent establishment maintained by the non-U.S. stockholder in the United States (as discussed above) or (b) the non-U.S. stockholder is an individual, has been present in the United States for 183 days or more during the taxable year, and certain other conditions are satisfied. For a corporate non-U.S. stockholder, distributions (both actual and deemed), and gains recognized upon the sale of our common stock that are effectively connected with a U.S. trade or business may, under certain circumstances, be subject to an additional "branch profits tax" (unless lowered or eliminated by an applicable income tax treaty). Non-U.S. stockholders of our common stock are encouraged to consult their own advisors as to the applicability of an income tax treaty in their individual circumstances.

In general, no U.S. source withholding taxes will be imposed on dividends paid by us to non-U.S. stockholders to the extent the dividends are designated as "interest related dividends" or "short term capital gain dividends." Under this exemption, interest related dividends and short term capital gain dividends generally represent distributions of interest or short term capital gain that would not have been subject to U.S. withholding tax at the source if they had been received directly by a non-U.S. stockholder, and that satisfy certain other requirements. No assurance can be given that we will distribute any interest related dividends or short term capital gain dividends.

If we distribute our net capital gain in the form of deemed rather than actual distributions (which we may do in the future), a non-U.S. stockholder will be entitled to a U.S. federal income tax credit or tax refund equal to the non-U.S. stockholder's allocable share of the tax we pay on the capital gain deemed to have been distributed. In order to obtain the refund, the non-U.S. stockholder must obtain a U.S. taxpayer identification number ("TIN") (if one has not been previously obtained) and file a U.S. federal income tax return even if the non-U.S. stockholder would not otherwise be required to obtain a U.S. TIN or file a U.S. federal income tax return.

Non-U.S. stockholders who have elected to participate in our "opt-in" dividend reinvestment plan will have their cash dividends and distributions automatically reinvested in additional shares of our common stock, rather than receiving cash dividends and distributions. Any dividends or distributions reinvested under the plan will nevertheless remain taxable to non-U.S. stockholders to the same extent as if those dividends were received in cash. In addition, we have the ability to declare a large portion of a dividend in shares of our common stock, even if a non-U.S. stockholder has not elected to participate in our dividend reinvestment plan, in which case, as long as a portion of the dividend is paid in cash (which portion could be as low as 20%) and certain requirements are met, the entire distribution will be treated as a dividend for U.S. federal income tax purposes. As a result, our non-U.S. stockholders will be taxed on 100% of the fair market value of the dividend paid entirely or partially in our common stock on the date the dividend is received in the same manner (and to the extent that non-U.S. stockholder is subject to U.S. federal income taxation) as a cash dividend (including the application of

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withholding tax rules described above), even if most or all of the dividend is paid in common stock. In such a circumstance, we may be required to withhold all or substantially all of the cash we would otherwise distribute to a non-U.S. stockholder.

*Backup Withholding and Other Required Withholding* 

We may be required to withhold U.S. federal income tax (i.e. backup withholding) from all taxable distributions to any non-corporate U.S. stockholder (i) who fails to furnish us with a correct taxpayer identification number or a certificate that such stockholder is exempt from backup withholding, or (ii) with respect to whom the Internal Revenue Service ("IRS") notifies us that such stockholder has failed to properly report certain interest and dividend income to the IRS and to respond to notices to that effect. An individual's taxpayer identification number is generally his or her social security number. Any amount withheld under backup withholding is allowed as a credit against the U.S. stockholder's federal income tax liability, provided that proper information is timely provided to the IRS.

Sections 1471-1474 of the Code and the U.S. Treasury and IRS guidance issued thereunder (collectively, "FATCA") generally require that we obtain information sufficient to identify the status of each shareholder under FATCA or under an applicable intergovernmental agreement (an "IGA") between the United States and a foreign government. If a shareholder fails to provide the requested information or otherwise fails to comply with FATCA or an IGA, we may be required to withhold under FATCA at a rate of 30% with respect to that shareholder on ordinary dividends it pays. The IRS and the Department of Treasury have issued proposed regulations providing that these withholding rules will not apply to the gross proceeds of share redemptions or capital gain dividends we pay. If a payment is subject to FATCA withholding, we are required to withhold even if such payment would otherwise be exempt from withholding under the rules applicable to foreign shareholders described above (e.g., interest-related dividends). In addition, subject to certain exceptions, this legislation also imposes a 30% withholding on payments to foreign entities that are not financial institutions unless the foreign entity certifies that it does not have a greater than 10% U.S. owner or provides the withholding agent with identifying information on each greater than 10% U.S. owner. Depending on the status of a non-U.S. stockholder and the status of the intermediaries through which they hold their shares, non-U.S. stockholders could be subject to this 30% withholding tax with respect to distributions on their shares and proceeds from the sale of their shares. Under certain circumstances, a non-U.S. stockholder might be eligible for refunds or credits of such taxes.

**All stockholders are urged to consult their tax advisers with respect to the U.S. federal income and withholding tax consequences, and state, local and non-U.S. tax consequences, of an investment in our common stock. We will not pay any additional amounts in respect to any amounts withheld.** 

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#### DESCRIPTION OF OUR SECURITIES
Our authorized capital stock consists of 100,000,000 shares of common stock, par value $0.001 per share, and 10,000,000 shares of preferred stock, par value $0.001 per share.

The following are our outstanding classes, and series thereof, of Securities as of February 23, 2024.

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| | | | |
|:---|:---|:---|:---|
| (1)<br> **Title of Class** | **(2)**<br>**Amount**<br>**Authorized** | **(3)**<br>**Amount**<br>**Held**<br>**by us or for**<br>**Our**<br>**Account** | **(4)**<br>**Amount**<br>**Outstanding**<br>**Exclusive of**<br>**Amounts Shown**<br>**Under(3)** |
|  Common Stock | 100,000,000 shares |  | 36,688,667 shares |
|  5.00% Notes due 2026 | $127937500 |  | $127937500 |
|  4.875% Notes due 2028 | $134550000 |  | $134550000 |
|  8.00% Notes due 2028 | $74750000 |  | $74750000 |

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The following description is a summary based on relevant provisions of our certificate of incorporation and bylaws and the Delaware General Corporation Law. This summary does not purport to be complete and is subject to, and qualified in its entirety by, the provisions of our certificate of incorporation and bylaws, as amended, and applicable provisions of the Delaware General Corporation Law.

#### Common Stock
All shares of our common stock have equal rights as to earnings, assets, dividends and voting and are duly authorized, validly issued, fully paid and nonassessable. Shares of our common stock have no preemptive, exchange, conversion or redemption rights and are freely transferable, except where their transfer is restricted by federal and state securities laws or by contract.

Distributions may be paid to the holders of our common stock if, as and when declared by our Board of Directors out of funds legally available therefor. In the event of our liquidation, dissolution or winding up, each share of our common stock would be entitled to share ratably in all of our assets that are legally available for distribution after we pay all debts and other liabilities and subject to any preferential rights of holders of our preferred stock, if any preferred stock is outstanding at such time.

Each share of our common stock is entitled to one vote on all matters submitted to a vote of stockholders, including the election of directors. Except as provided with respect to any other class or series of stock, the holders of our common stock will possess exclusive voting power. Except as otherwise provided by statute, by the rules of Nasdaq or other applicable stock exchange, by our certificate of incorporation or by our bylaws, in all matters other than the election of directors, the affirmative vote of the majority of shares present or represented by proxy at a meeting of our stockholders and entitled to vote will be the act of the stockholders. Except as otherwise provided by statute, by our certificate of incorporation or by our bylaws, directors shall be elected by a plurality of the votes of the shares present or represented by proxy at a meeting of our stockholders and entitled to vote on the election of directors. Our common stock is listed on Nasdaq under the ticker symbol "GAIN."

#### Preferred Stock
Our certificate of incorporation gives the board of directors the authority, without further action by stockholders, to issue up to 10,000,000 shares of preferred stock in one or more series and to fix the rights, preferences, privileges, qualifications and restrictions granted to or imposed upon such preferred stock, including dividend rights, conversion rights, voting rights, rights and terms of redemption, and liquidation preference, any or all of which may be greater than the rights of the common stock. Thus, the board of directors could authorize the issuance of shares of preferred stock with terms and conditions which could have the effect of delaying,

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deferring or preventing a transaction or a change in control that might involve a premium price for holders of our common stock or otherwise be in their best interest. The issuance of preferred stock could adversely affect the voting power of holders of common stock and reduce the likelihood that such holders will receive dividend payments and payments upon liquidation, and could also decrease the market price of our common stock.

#### Subscription Rights

#### General
We may issue subscription rights to our stockholders to purchase common stock or preferred stock. Subscription rights may be issued independently or together with any other offered security and may or may not be transferable by the person purchasing or receiving the subscription rights. In connection with any subscription rights offering to our stockholders, we may enter into a standby underwriting arrangement with one or more underwriters pursuant to which such underwriters would purchase any offered Securities remaining unsubscribed after such subscription rights offering to the extent permissible under applicable law. In connection with a subscription rights offering to our stockholders, we would distribute certificates evidencing the subscription rights and a prospectus supplement to our stockholders on the record date that we set for receiving subscription rights in such subscription rights offering.

The applicable prospectus supplement would describe the following terms of subscription rights in respect of which this prospectus is being delivered:

• the period of time the offering would remain open (which in no event would be less than fifteen business days);

• the title of such subscription rights;

• the exercise price for such subscription rights;

• the ratio of the offering (which in no event would exceed one new share of common stock for each three rights held);

• the number of such subscription rights issued to each stockholder;

• the extent to which such subscription rights are transferable;

• if applicable, a discussion of the material U.S. federal income tax considerations applicable to the issuance or exercise of such subscription rights;

• the date on which the right to exercise such subscription rights shall commence, and the date on which such rights shall expire (subject to any extension);

• the extent to which such subscription rights include an over-subscription privilege with respect to unsubscribed securities;

• if applicable, the material terms of any standby underwriting or other purchase arrangement that we may enter into in connection with the subscription rights offering; and

• any other terms of such subscription rights, including terms, procedures and limitations relating to the exchange and exercise of such subscription rights.

#### Exercise of Subscription Rights
Each subscription right would entitle the holder of the subscription right to purchase for cash such amount of shares of common stock, or preferred stock, at such exercise price as shall in each case be set forth in, or be determinable as set forth in, the prospectus supplement relating to the subscription rights offered thereby. Subscription rights may be exercised at any time up to the close of business on the expiration date for such subscription rights set forth in the prospectus supplement. After the close of business on the expiration date, all unexercised subscription rights would become void.

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Subscription rights may be exercised as set forth in the prospectus supplement relating to the subscription rights offered thereby. Upon receipt of payment and the subscription rights certificate properly completed and duly executed at the corporate trust office of the subscription rights agent or any other office indicated in the prospectus supplement we will forward, as soon as practicable, the shares of common stock purchasable upon such exercise. We may determine to offer any unsubscribed offered securities directly to persons other than stockholders, to or through agents, underwriters or dealers or through a combination of such methods, including pursuant to standby underwriting arrangements, as set forth in the applicable prospectus supplement.

#### Warrants
The following is a general description of the terms of the warrants we may issue from time to time. Particular terms of any warrants we offer will be described in the prospectus supplement relating to such warrants.

We may issue warrants to purchase shares of our common stock, preferred stock or debt securities. Such warrants may be issued independently or together with shares of common or preferred stock or other equity or debt securities and may be attached or separate from such securities. We will issue each series of warrants under a separate warrant agreement to be entered into between us and a warrant agent. The warrant agent will act solely as our agent and will not assume any obligation or relationship of agency for or with holders or beneficial owners of warrants.

A prospectus supplement will describe the particular terms of any series of warrants we may issue, including the following:

• the title of such warrants;

• the aggregate number of such warrants;

• the price or prices at which such warrants will be issued;

• the currency or currencies, including composite currencies, in which the price of such warrants may be payable;

• if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;

• in the case of warrants to purchase debt securities, the principal amount of debt securities purchasable upon exercise of one warrant and the price at which and the currency or currencies, including composite currencies, in which such principal amount may be purchased upon such exercise;

• in the case of warrants to purchase common stock or preferred stock, the number of shares of common or preferred stock purchasable upon exercise of one warrant and the price at which and the currency or currencies, including composite currencies, in which these shares may be purchased upon such exercise;

• the date on which the right to exercise such warrants shall commence and the date on which such right will expire;

• whether such warrants will be issued in registered form or bearer form;

• if applicable, the minimum or maximum amount of such warrants which may be exercised at any one time;

• if applicable, the date on and after which such warrants and the related securities will be separately transferable;

• information with respect to book-entry procedures, if any;

• the terms of the securities issuable upon exercise of the warrants;

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• if applicable, a discussion of certain U.S. federal income tax considerations; and

• any other terms of such warrants, including terms, procedures and limitations relating to the exchange and exercise of such warrants.

We and the warrant agent may amend or supplement the warrant agreement for a series of warrants without the consent of the holders of the warrants issued thereunder to effect changes that are not inconsistent with the provisions of the warrants and that do not materially and adversely affect the interests of the holders of the warrants.

Prior to exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including the right to receive distributions or dividends, if any, or payments upon our liquidation, dissolution or winding up or to exercise any voting rights.

Under the 1940 Act, we may generally only offer warrants (except for warrants expiring not later than 120 days after issuance and issued exclusively and ratably to a class of our security holders) on the condition that (1) the warrants expire by their terms within ten years; (2) the exercise or conversion price is not less than the current market value of the securities underlying the warrants at the date of issuance; (3) our stockholders authorize the proposal to issue such warrants (our stockholders approved such a proposal to issue long-term rights, including warrants, in connection with our 2008 annual meeting of stockholders) and a "required majority" of our Board of Directors approves such issuance on the basis that the issuance is in the best interests of Gladstone Investment and our stockholders; and (4) if the warrants are accompanied by other securities, the warrants are not separately transferable unless no class of such warrants and the securities accompanying them has been publicly distributed. A "required majority" of our Board of Directors is a vote of both a majority of our directors who have no financial interest in the transaction and a majority of the directors who are not interested persons of the company. The 1940 Act also provides that the amount of our voting securities that would result from the exercise of all outstanding warrants, options and subscription rights at the time of issuance may not exceed 25% of our outstanding voting securities.

#### Debt Securities
Any debt securities that we issue may be senior or subordinated in priority of payment. If we offer debt securities under this prospectus, we will provide a prospectus supplement that describes the ranking, whether senior or subordinated, the specific designation, the aggregate principal amount, the purchase price, the maturity, the redemption terms, the interest rate or manner of calculating the interest rate, the time of payment of interest, if any, the terms for any conversion or exchange, including the terms relating to the adjustment of any conversion or exchange mechanism, the listing, if any, on a securities exchange, the name and address of the trustee and any other specific terms of the debt securities.

The description of our debt securities included in Exhibit 4.5 of our most recent Annual Report on Form 10-K or included in any subsequent Quarterly Report on Form 10-Q is incorporated by reference herein.

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#### CERTAIN PROVISIONS OF DELAWARE LAW AND OUR

#### CERTIFICATE OF INCORPORATION AND BYLAWS
*The following description of certain provisions of Delaware law and of our amended and restated certificate of incorporation (our "certificate of incorporation") and our amended and restated bylaws, as amended (our "bylaws"), is only a summary. For a complete description, we refer you to the Delaware General Corporation Law, our certificate of incorporation and our bylaws. We have filed our certificate of incorporation and bylaws, as amended, as exhibits to the registration statement of which this prospectus is a part.* 

#### Classified Board of Directors
Pursuant to our certificate of incorporation, our Board of Directors is divided into three classes of directors. Each class consists, as nearly as possible, of one-third of the total number of directors, and each class has a three-year term. The holders of outstanding shares of common stock elect our directors. Any director elected to fill a vacancy shall serve for the remainder of the full term of the class in which the vacancy occurred and until a successor is elected and qualified. Holders of shares of our stock have no right to cumulative voting in the election of directors. Consequently, at each annual meeting of our stockholders, the holders of a plurality of the shares of our common stock are able to elect all of the successors to the class of directors whose term expires at such meeting.

Our classified board could have the effect of making the replacement of incumbent directors more time consuming and difficult. Because our directors may only be removed for cause, at least two annual meetings of stockholders, instead of one, will generally be required to effect a change in a majority of our Board of Directors. Thus, our classified board could increase the likelihood that incumbent directors will retain their positions. The staggered terms of directors may delay, defer or prevent a tender offer or an attempt to change control of us or another transaction that might involve a premium price for our common stock that might be in the best interest of our stockholders.

#### Removal of Directors
Any director may be removed only for cause by the stockholders upon the affirmative vote of at least two-thirds of all the votes entitled to be cast at a meeting called for the purpose of the proposed removal. The notice of the meeting shall indicate that the purpose, or one of the purposes, of the meeting is to determine if the director shall be removed.

#### Business Combinations
Section 203 of the Delaware General Corporation Law generally prohibits "business combinations" between us and an "interested stockholder" for three years after the date of the transaction in which the person became an interested stockholder. In general, Delaware law defines an interested stockholder as any entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation and any entity or person affiliated with or controlling, or controlled by, the entity or person. These business combinations include:

• Any merger or consolidation involving the corporation and the interested stockholder;

• Any sale, transfer, pledge or other disposition involving the interested stockholder of 10% or more of the assets of the corporation;

• Subject to exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation to the interested stockholder; or

• The receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial benefits provided by or through the corporation.

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Section 203 permits certain exemptions from its provisions for transactions in which:

• Prior to the date of the transaction, the board of directors of the corporation approved either the business combination or the transaction which resulted in the stockholder becoming an interested stockholder;

• The interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the number of shares outstanding (a) shares owned by persons who are directors and also officers, and (b) shares owned by employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or

• On or subsequent to the date of the transaction, the business combination is approved by the board of directors and authorized at an annual or special meeting of stockholders, and not by written consent, by the affirmative vote of at least 66 2/3% of the outstanding voting stock that is not owned by the interested stockholder.

#### Merger; Amendment of Certificate of Incorporation
Under Delaware law, we will not be able to amend our certificate of incorporation or merge with another entity unless approved by the affirmative vote of stockholders holding at least a majority of the shares entitled to vote on the matter.

#### Term and Termination
Our certificate of incorporation provides for us to have a perpetual existence. Pursuant to our certificate of incorporation, and subject to the provisions of any of our classes or series of stock then outstanding and the approval by a majority of the entire Board of Directors, our stockholders, at any meeting thereof, by the affirmative vote of a majority of all of the votes entitled to be cast on the matter, may approve a plan of liquidation and dissolution.

#### Advance Notice of Director Nominations and New Business
Our bylaws provide that, with respect to an annual meeting of stockholders, nominations of persons for election to our Board of Directors and the proposal of business to be considered by stockholders at the annual meeting may be made only:

• pursuant to our notice of the meeting;

• by our Board of Directors; or

• by a stockholder who was a stockholder of record both at the time of the provision of notice and at the time of the meeting who is entitled to vote at the meeting and has complied with the advance notice procedures set forth in our bylaws.

With respect to special meetings of stockholders, only the business specified in our notice of meeting may be brought before the meeting of stockholders and nominations of persons for election to our Board of Directors may be made only:

• pursuant to our notice of the meeting;

• by our Board of Directors; or

• provided that our Board of Directors has determined that directors shall be elected at such meeting, by a stockholder who was a stockholder of record both at the time of the provision of notice and at the time of the meeting who is entitled to vote at the meeting and has complied with the advance notice provisions set forth in our bylaws.

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#### Preferred Stock
Our certificate of incorporation gives our Board of Directors the authority, without further action by stockholders, to issue shares of preferred stock in one or more series and to fix the rights, preferences, privileges, qualifications and restrictions granted to or imposed upon such preferred stock, including dividend rights, conversion rights, voting rights, rights and terms of redemption, and liquidation preference, any or all of which may be greater than the rights of the common stock. Thus, our Board of Directors could authorize the issuance of shares of preferred stock with terms and conditions which could have the effect of delaying, deferring or preventing a transaction or a change in control that might involve a premium price for holders of our common stock or otherwise be in their best interest. The issuance of preferred stock could adversely affect the voting power of holders of common stock and reduce the likelihood that such holders will receive dividend payments and payments upon liquidation, and could also decrease the market price of our common stock.

#### Possible Anti-Takeover Effect of Certain Provisions of Delaware Law and of Our Certificate of Incorporation and Bylaws
The business combination provisions of Delaware law, the provisions of our bylaws regarding the classification of our Board of Directors and the Board of Directors' ability to issue preferred stock with terms and conditions that could have a priority as to distributions and amounts payable upon liquidation over the rights of the holders of our common stock, and the advance notice provisions of our bylaws could have the effect of delaying, deferring or preventing a transaction or a change in the control that might involve a premium price for holders of common stock or otherwise be in their best interest.

#### Limitation on Liability of Directors and Officers; Indemnification and Advance of Expenses
Our certificate of incorporation eliminates the liability of directors to the maximum extent permitted by Delaware law. In addition, our bylaws require us to indemnify our directors and executive officers, and allow us to indemnify other employees and agents, to the fullest extent permitted by law, subject to the requirements of the 1940 Act. Our bylaws obligate us to indemnify any present or former director or officer or any individual who, while a director or officer and at our request, serves or has served another corporation, real estate investment trust, partnership, joint venture, trust, employee benefit plan or other enterprise as a director, officer, partner or trustee, from and against any claim or liability to which that person may become subject or which that person may incur by reason of his or her status as a present or former director or officer and to pay or reimburse their reasonable expenses in advance of final disposition of a proceeding. The certificate of incorporation and bylaws also permit us to indemnify and advance expenses to any person who served a predecessor of us in any of the capacities described above and any of our employees or agents or any employees or agents of our predecessor. In accordance with the 1940 Act, we will not indemnify any person for any liability to which such person would be subject by reason of such person's willful misfeasance, bad faith, gross negligence or reckless disregard of the duties involved in the conduct of his or her office.

Delaware law requires a corporation to indemnify a present or former director or officer who has been successful, on the merits or otherwise, in the defense of any proceeding to which he or she is made a party by reason of his or her service in that capacity. Delaware law permits a corporation to indemnify its present and former directors and officers, or any other person who is or was an employee or agent, or is or was serving at the request of a corporation as a director, officer, employee or agent of another entity, against liability for expenses, judgments, fines and amounts paid in settlement actually and reasonably incurred if such person acted in good faith and in a manner reasonably believed to be in or not opposed to the best interests of the corporation. In the case of a criminal proceeding, Delaware law further requires that the person to be indemnified have no reasonable cause to believe his or her conduct was unlawful. In the case of an action or suit by or in the right of a corporation to procure a judgment in its favor by reason of such person's service to the corporation, Delaware law provides that no indemnification shall be made with respect to any claim, issue or matter as to which such person has been adjudged liable to the corporation, unless and only to the extent that the court in which such an

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action or suit is brought determines, in view of all the circumstances of the case, that the person is fairly and reasonably entitled to indemnity. Insofar as certain members of our senior management team may from time to time serve, at the request of our Board of Directors, as directors of one or more of our portfolio companies, we may have indemnification obligations under our bylaws with respect to acts taken by our portfolio companies.

Any payment to an officer or director as indemnification under our governing documents or applicable law or pursuant to any agreement to hold such person harmless is recoverable only out of our assets and not from our stockholders. Indemnification could reduce the legal remedies available to us and our stockholders against the indemnified individuals. This provision for indemnification of our directors and officers does not reduce the exposure of our directors and officers to liability under federal or state securities laws, nor does it limit a stockholder's ability to obtain injunctive relief or other equitable remedies for a violation of a director's or an officer's duties to us or to our stockholders, although these equitable remedies may not be effective in some circumstances.

In addition to any indemnification to which our directors and officers are entitled pursuant to our certificate of incorporation and bylaws and the Delaware General Corporation Law, our certificate of incorporation and bylaws provide that we may indemnify other employees and agents to the fullest extent permitted under Delaware law, whether they are serving us or, at our request, any other entity, including our Adviser and our Administrator.

The general effect to investors of any arrangement under which any person who controls us or any of our directors, officers or agents is insured or indemnified against liability is a potential reduction in distributions to our stockholders resulting from our payment of premiums associated with liability insurance. In addition, indemnification could reduce the legal remedies available to us and to our stockholders against our officers, directors and agents. The SEC takes the position that indemnification against liabilities arising under the Securities Act is against public policy and unenforceable. As a result, indemnification of our directors and officers and of our Adviser or its affiliates may not be allowed for liabilities arising from or out of a violation of state or federal securities laws. Indemnification will be allowed for settlements and related expenses of lawsuits alleging securities laws violations and for expenses incurred in successfully defending any lawsuit, provided that a court either:

• approves the settlement and finds that indemnification of the settlement and related costs should be made; or

• dismisses with prejudice or makes a successful adjudication on the merits of each count involving alleged securities law violations as to the particular indemnitee and a court approves the indemnification.

#### Conflict with 1940 Act
Our bylaws provide that, if and to the extent that any provision of the Delaware General Corporation Law or any provision of our certificate of incorporation or bylaws conflicts with any provision of the 1940 Act, the applicable provision of the 1940 Act will control.

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#### SHARE REPURCHASES
Shares of closed-end investment companies, including BDCs, frequently trade at discounts to NAV. We cannot predict whether our shares will trade above, at or below NAV. The market price of our common stock is determined by, among other things, the supply and demand for our shares, our investment performance and investor perception of our overall attractiveness as an investment as compared with alternative investments. Our Board of Directors may authorize our officers, in their discretion and subject to compliance with the 1940 Act and other applicable law, to purchase on the open market or in privately negotiated transactions, outstanding shares of our common stock in the event that our shares trade at a discount to NAV. We cannot assure you that we will ever conduct any open market purchases and if we do conduct open market purchases, we may terminate them at any time.

In addition, if our shares publicly trade for a substantial period of time at a substantial discount to our then current NAV per share, our Board of Directors may consider authorizing periodic repurchases of our shares or other actions designed to eliminate the discount. Our Board of Directors could consider any relevant factors in determining whether to take any such actions, including the effect of such actions on our status as a RIC under the Code and the availability of cash to finance these repurchases in view of the restrictions on our ability to borrow. We cannot assure you that any share repurchases will be made or that if made, they will reduce or eliminate market discount. Should we make any such repurchases in the future, we expect that we would make them at prices at or below the then current NAV per share. Any such repurchase would cause our total assets to decrease, which may have the effect of increasing our expense ratio. We may borrow money to finance the repurchase of shares subject to the limitations described in this prospectus. Any interest on such borrowing for this purpose would reduce our net income.

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#### PROXY VOTING POLICIES AND PROCEDURES
We have delegated our proxy voting responsibility to the Adviser. The proxy voting policies and procedures of the Adviser are set out below. The guidelines are reviewed periodically by the Adviser and our directors who are not "interested persons," and, accordingly, are subject to change.

#### Introduction
As an investment adviser registered under the Advisers Act, the Adviser has a fiduciary duty to act solely in our best interests. As part of this duty, the Adviser recognizes that it must vote our securities in a timely manner free of conflicts of interest and in our best interests.

The Adviser's policies and procedures for voting proxies for its investment advisory clients are intended to comply with Section 206 of, and Rule 206(4)-6 under, the Advisers Act.

#### Proxy Policies
The Adviser votes proxies relating to our portfolio securities in what it perceives to be the best interest of our stockholders. The Adviser reviews on a case-by-case basis each proposal submitted to a stockholder vote to determine its effect on the portfolio securities we hold. In most cases the Adviser will vote in favor of proposals that the Adviser believes are likely to increase the value of the portfolio securities we hold.

Although the Adviser will generally vote against proposals that may have a negative effect on our portfolio securities, the Adviser may vote for such a proposal if there exist compelling long-term reasons to do so.

Our proxy voting decisions are made by our Adviser's portfolio managers. To ensure that the Adviser's vote is not the product of a conflict of interest, the Adviser requires that (1) anyone involved in the decision-making process disclose to our Adviser's investment committee any potential conflict that he or she is aware of and any contact that he or she has had with any interested party regarding a proxy vote; and (2) employees involved in the decision-making process or vote administration are prohibited from revealing how the Adviser intends to vote on a proposal in order to reduce any attempted influence from interested parties. Where conflicts of interest may be present, the Adviser will disclose such conflicts to us, including our independent directors and may request guidance from us on how to vote such proxies.

#### Proxy Voting Records
You may obtain information without charge about how the Adviser voted proxies by making a written request for proxy voting information to:

Michael LiCalsi, General Counsel and Secretary

c/o Gladstone Investment Corporation

1521 Westbranch Drive

Suite 100

McLean, VA 22102

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#### PLAN OF DISTRIBUTION
We may offer the Securities through underwriters or dealers, directly to one or more purchasers, including existing stockholders in a rights offering, or through agents or through a combination of any such methods of sale. In the case of a rights offering, the applicable prospectus supplement will set forth the number of shares of our common stock issuable upon the exercise of each right and the other terms of such rights offering. Any underwriter or agent involved in the offer and sale of Securities will be named in the applicable prospectus supplement. Any prospectus supplement or supplements will also describe the terms of the offering of Securities, including: the amount and purchase price of Securities and the proceeds we will receive from the sale; any over-allotment options under which underwriters may purchase additional Securities from us; any agency fees or underwriting discounts and other items constituting agents' or underwriters' compensation; the public offering price; any discounts or concessions allowed or re-allowed or paid to dealers; and any securities exchange or market on which the Securities may be listed.

The distribution of the Securities may be effected from time to time in one or more transactions at a fixed price or prices, which may be changed, in "at the market offerings" within the meaning of Rule 415(a)(4) of the Securities Act, at prevailing market prices at the time of sale, at prices related to such prevailing market prices, or at negotiated prices. The price at which Securities may be distributed may represent a discount from prevailing market prices, provided, however, that in the case of our common stock, the offering price per share less any underwriting commissions or discounts must equal or exceed the NAV per share of our common stock except (i) in connection with a rights offering to our existing stockholders, (ii) with the consent of the majority of our outstanding voting securities (as defined in the 1940 Act), or (iii) under such other circumstances as the SEC may permit.

In connection with the sale of the Securities, underwriters or agents may receive compensation from us or from purchasers of the Securities, for whom they may act as agents, in the form of discounts, concessions or commissions. Our common stockholders will indirectly bear such fees and expenses as well as any other fees and expenses incurred by us in connection with any sale of Securities. Underwriters may sell the Securities to or through dealers and such dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for whom they may act as agents. Underwriters, dealers and agents that participate in the distribution of the Securities may be deemed to be underwriters under the Securities Act, and any discounts and commissions they receive from us and any profit realized by them on the resale of the Securities may be deemed to be underwriting discounts and commissions under the Securities Act. Any such underwriter or agent will be identified and any such compensation received from us will be described in the applicable prospectus supplement. The maximum commission or discount to be received by any FINRA member or independent broker-dealer will not exceed 10%.

Any underwriter may engage in over-allotment, stabilizing transactions, short-covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Over-allotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum price. Syndicate-covering or other short-covering transactions involve purchases of the Securities, either through exercise of the over-allotment option or in the open market after the distribution is completed, to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the Securities originally sold by the dealer are purchased in a stabilizing or covering transaction to cover short positions. Those activities may cause the price of the Securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time.

Any underwriters that are qualified market makers on Nasdaq may engage in passive market making transactions in our common stock on Nasdaq in accordance with Regulation M under the Exchange Act, during the business day prior to the pricing of the offering, before the commencement of offers or sales of our common stock. Passive market makers must comply with applicable volume and price limitations and must be identified

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as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker's bid, however, the passive market maker's bid must then be lowered when certain purchase limits are exceeded. Passive market making may stabilize the market price of the Securities at a level above that which might otherwise prevail in the open market and, if commenced, may be discontinued at any time.

We may sell the Securities directly or through agents we designate from time to time. We will name any agent involved in the offering and sale of the Securities and we will describe any commissions we will pay the agent in the prospectus supplement. Unless the prospectus supplement states otherwise, our agent will act on a best-efforts basis for the period of its appointment.

Unless otherwise specified in the applicable prospectus supplement, each class or series of Securities will be a new issue with no trading market, other than our common stock, which is traded on Nasdaq. We may elect to list any other class or series of Securities on any exchanges, but we are not obligated to do so. We cannot guarantee the liquidity of the trading markets for any Securities.

We may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with those derivatives, the third parties may sell Securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of stock and may use securities received from us in settlement of those derivatives to close out any related open borrowings of stock. The third parties in such sale transactions will be underwriters and, if not identified in this prospectus, will be identified in the applicable prospectus supplement (or a post-effective amendment).

Any of our common stock sold pursuant to a prospectus supplement will be listed on Nasdaq, or another exchange on which our common stock is traded.

Under agreements into which we may enter, underwriters, dealers and agents who participate in the distribution of the Securities may be entitled to indemnification by us against certain liabilities, including liabilities under the Securities Act. Underwriters, dealers and agents may engage in transactions with, or perform services for, us in the ordinary course of business.

If so indicated in the applicable prospectus supplement, we will authorize underwriters or other persons acting as our agents to solicit offers by certain institutions to purchase the Securities from us pursuant to contracts providing for payment and delivery on a future date. Institutions with which such contracts may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and others, but in all cases such institutions must be approved by us. The obligations of any purchaser under any such contract will be subject to the condition that the purchase of the Securities shall not at the time of delivery be prohibited under the laws of the jurisdiction to which such purchaser is subject. The underwriters and such other agents will not have any responsibility in respect of the validity or performance of such contracts. Such contracts will be subject only to those conditions set forth in the prospectus supplement, and the prospectus supplement will set forth the commission payable for solicitation of such contracts.

In order to comply with the securities laws of certain states, if applicable, the Securities offered hereby will be sold in such jurisdictions only through registered or licensed brokers or dealers. In addition, in certain states, the Securities may not be sold unless they have been registered or qualified for sale in the applicable state or an exemption from the registration or qualification requirement is available and is complied with.

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#### BROKERAGE ALLOCATION AND OTHER PRACTICES
Since we generally acquire and dispose of our investments in privately negotiated transactions, we will infrequently use securities brokers or dealers in the normal course of our business. Subject to policies established by our Board of Directors, our Adviser will be primarily responsible for ensuring the execution of transactions involving publicly traded securities and the review of brokerage commissions in respect thereof, if any. In the event that our Adviser ensures the execution of such transactions, we do not expect our Adviser to execute transactions through any particular broker or dealer, but we would expect our Adviser to seek to obtain the best net results for us, taking into account such factors as price (including any applicable brokerage commission or dealer spread), size of order, difficulty of execution, and operational facilities of the broker dealer and the broker dealer's risk and skill in positioning blocks of securities. While we expect that our Adviser generally will seek reasonably competitive trade execution costs, we will not necessarily pay the lowest spread or commission available. Subject to applicable legal requirements, our Adviser may select a broker dealer based partly upon brokerage or market research services provided to us, our Adviser and any of its other clients, if any. In return for such services, we may pay a higher commission than other broker dealers would charge if our Adviser determines in good faith that such commission is reasonable in relation to the value of the brokerage and research services provided by such broker dealer viewed in terms either of the particular transaction or our Adviser's overall responsibilities with respect to all of our Adviser's clients.

We have not paid any brokerage commissions during the three most recent fiscal years to any affiliated person of us or our Adviser.

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#### CUSTODIAN, TRANSFER AND DIVIDEND PAYING AGENT AND REGISTRAR
The securities we hold in our portfolio companies are held under a custodian agreement with The Bank of New York Mellon Corp. The address of the custodian is: 500 Ross Street, Suite 935, Pittsburgh, Pennsylvania 15262. Our assets are held under bank custodianship in compliance with the 1940 Act. Securities held through our wholly-owned subsidiary, Business Investment, are held under a custodian agreement with The Bank of New York Mellon Corp., which acts as collateral custodian pursuant to the Credit Facility. The address of the collateral custodian is 2322 French Settlement Road, Suite 100, Dallas, Texas 75212. Computershare acts as our transfer and dividend paying agent and registrar. The principal business address of Computershare is 150 Royall Street, Canton, Massachusetts 02021, telephone number (781) 575-2000. Computershare also maintains an internet website at *www.computershare.com* and one specifically for shareholders at *www.computershare.com/investor.*

#### LEGAL MATTERS
The legality of Securities offered hereby will be passed upon for us by Kirkland & Ellis LLP, Washington, D.C. Certain legal matters will be passed upon for the underwriters, if any, by the counsel named in the accompanying prospectus supplement.

#### EXPERTS
The financial statements incorporated in this Prospectus by reference to the Annual Report on Form 10-K for the year ended March 31, 2023 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting. The address of PricewaterhouseCoopers LLP is 655 New York Avenue NW, Washington, DC 20001.

#### AVAILABLE INFORMATION
We have filed with the SEC a registration statement on Form N-2 under the Securities Act with respect to the Securities offered by this prospectus. This prospectus, which is a part of the registration statement, does not contain all of the information set forth in the registration statement or exhibits and schedules thereto. For further information with respect to our business and our Securities, reference is made to the registration statement, including the amendments, exhibits and schedules thereto.

We are a public company and file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are also available to the public at the SEC's website at *www.sec.gov*. We also make available free of charge through our website our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act as well as our definitive proxy statement and Section 16 reports on Forms 3, 4 and 5. Our website address is www.gladstoneinvestment.com. However, the information located on, or accessible from, our website is not, and shall not be deemed to be, except as described below, a part of this prospectus or any accompanying prospectus supplement or incorporated into any other filings that we make with the SEC.

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#### INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE
This prospectus is part of a registration statement that we have filed with the SEC. The SEC allows us to "incorporate by reference" the information that we file with it which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to comprise a part of this prospectus from the date we file that document. Any reports filed by us with the SEC after the date of this prospectus and before the date that the offering of the securities by means of this prospectus is terminated will automatically update and, where applicable, supersede any information contained in this prospectus or incorporated by reference in this prospectus.

We previously filed the following documents with the SEC, and such filings are incorporated by reference into this prospectus.

• Our Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/1321741/000132174123000011/gain-20230331.htm) for the fiscal year ended March 31, 2023, filed with the SEC on May 10, 2023 (including portions of our Definitive Proxy Statement for the 2023 Annual Meeting of Stockholders incorporated therein by reference);

• Our Quarterly Reports on Form 10-Q for the quarters ended June 30, 2023, September 30, 2023, and December 31, 2023, filed with the SEC on [August 2, 2023](http://www.sec.gov/Archives/edgar/data/1321741/000132174123000021/gain-20230630.htm) , [November 1, 2023](http://www.sec.gov/Archives/edgar/data/1321741/000132174123000026/gain-20230930.htm) and [February 6, 2024](http://www.sec.gov/Archives/edgar/data/1321741/000132174124000005/gain-20231231.htm) , respectively;

• Our Current Reports on Form 8-K, filed with the SEC on [April 14, 2023](http://www.sec.gov/Archives/edgar/data/1321741/000119312523102121/d496721d8k.htm) , [May 24, 2023](http://www.sec.gov/Archives/edgar/data/1321741/000119312523153046/d498916d8k.htm) , [May 31, 2023](http://www.sec.gov/Archives/edgar/data/1321741/000119312523157946/d512241d8k.htm) , [August 3, 2023](http://www.sec.gov/Archives/edgar/data/1321741/000119312523202908/d397644d8k.htm) , [August 8, 2023](http://www.sec.gov/Archives/edgar/data/1321741/000119312523205188/d534198d8k.htm) , [October 31, 2023](http://www.sec.gov/Archives/edgar/data/1321741/000119312523267202/d455400d8k.htm) , [January 5, 2024](http://www.sec.gov/Archives/edgar/data/1321741/000119312524003368/d706956d8k.htm) and [February 6, 2024](http://www.sec.gov/Archives/edgar/data/1321741/000119312524024265/d745489d8k.htm) ; and

• The description of our common stock contained in our Amendment No. 1 to our Registration Statement on [Form 8-A](http://www.sec.gov/Archives/edgar/data/1321741/000095013305002739/w10190e8va12gza.htm) (File No. 814-00704), filed with the SEC on June 21, 2005, including any amendment or report filed for the purpose of updating such description.

We also incorporate by reference into this prospectus additional documents that we may file with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act, from the filing of this prospectus until all of the securities offered by this prospectus have been sold or we otherwise terminate the offering of these securities, including all filings made after the date of the initial filing of the registration statement of which this prospectus is a part and prior to the effectiveness of the registration statement; provided, however, that information "furnished" under Item 2.02 or Item 7.01 of Form 8-K or other information "furnished" to the SEC which is not deemed filed is not incorporated by reference in this prospectus and any accompanying prospectus supplement. Information that we subsequently file with the SEC will automatically update and may supersede information in this prospectus, any accompanying prospectus supplement and information previously filed with the SEC.

These filings may also be accessed on the investors section of our website at *www.gladstoneinvestment.com*. Information contained on our website is not incorporated by reference into this prospectus. You may also request a copy of these filings (other than exhibits, unless the exhibits are specifically incorporated by reference into these documents) at no cost by writing, emailing or calling Investor Relations at the following address and telephone number:

Investor Relations

Gladstone Investment Corporation

1521 Westbranch Drive, Suite 100

McLean, Virginia 22102

(703) 287-5893

investment@gladstonecompanies.com

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![LOGO](g18863g98x33.jpg)

### $60,000,000

### 6.875% Notes due 2028

#### PROSPECTUS SUPPLEMENT

#### Sole Book-Running Manager
B. Riley Securities

#### November 6, 2025