# EDGAR Filing Document

**Accession Number:** 0001190935
**File Stem:** 0001193125-26-280733
**Filing Date:** 2026-6
**Character Count:** 12484
**Document Hash:** 394ebc9ef46f224f431f0a889d27573e
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-280733.hdr.sgml**: 20260624

**ACCESSION NUMBER**: 0001193125-26-280733

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 12

**CONFORMED PERIOD OF REPORT**: 20260623

**ITEM INFORMATION**: Other Events

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20260624

**DATE AS OF CHANGE**: 20260624

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** PIMCO CORPORATE & INCOME OPPORTUNITY FUND
- **CENTRAL INDEX KEY:** 0001190935

**ORGANIZATION NAME:**
- **EIN:** 466121513
- **FISCAL YEAR END:** 0630

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 811-21238
- **FILM NUMBER:** 261115130

**BUSINESS ADDRESS:**
- **STREET 1:** 1633 BROADWAY
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10019
- **BUSINESS PHONE:** 212-739-4000

**MAIL ADDRESS:**
- **STREET 1:** 1633 BROADWAY
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10019

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** PIMCO CORPORATE OPPORTUNITY FUND
- **DATE OF NAME CHANGE:** 20021022

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** PIMCO CORPORATE ADVANTAGE FUND
- **DATE OF NAME CHANGE:** 20020919

?xml version='1.0' encoding='ASCII'? 8-K

### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### WASHINGTON, DC 20549

### FORM 8-K

#### CURRENT REPORT

#### PURSUANT TO SECTION 13 OR 15(D)

#### OF THE SECURITIES EXCHANGE ACT OF 1934

#### Date of report (Date of earliest event reported) June 23, 2026

## PIMCO Corporate & Income Opportunity Fund

#### (Exact Name of Registrant as Specified in Its Charter)

---

| | | |
|:---|:---|:---|
| **Massachusetts** | **811-21238** | **46-6121513** |
| (State or other jurisdiction<br>of incorporation) | (Commission File Number) | (IRS Employer<br>Identification No.) |

---

---

| | |
|:---|:---|
| **1633 Broadway**<br> **New York, NY** | **10019** |
| (Address of principal executive offices) | (Zip Code) |

---

(844) 337-4626

(Registrant's telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

---

| | | |
|:---|:---|:---|
| **Title of each class** | **Trading<br>Symbol(s)** | **Name of each exchange<br>on which registered** |
| Common shares | PTY | New York Stock Exchange |

---

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

------

#### Item 8.01 Other Events.
On June 23, 2026, the Board of Trustees approved a change to the Fund's 80% investment policy. Effective August 28, 2026, the Fund invests, under normal circumstances, at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in corporate debt obligations of varying maturities and/or income-producing investments, which may include those of non-corporate issuers. The supplement to the Fund's prospectus and statement of additional information disclosing this change is attached hereto as Exhibit 99.1.

#### Item 9.01 Financial Statements and Exhibits.

---

| | |
|:---|:---|
| (d) | Exhibits |
| 99.1 | [Supplement, dated June 24, 2026](d120429dex991.htm) |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) |

---

------

#### SIGNATURE
Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

---

| | |
|:---|:---|
| PIMCO Corporate & Income Opportunity Fund | PIMCO Corporate & Income Opportunity Fund |
| By: | /s/ Ryan G. Leshaw |
| Name: | Ryan G. Leshaw |
| Title: | Chief Legal Officer and Secretary |

---

Date: June 24, 2026

## Exhibit 99.1

**PIMCO Corporate & Income Opportunity Fund** 

**(the "Fund")** 

**Important Notice Regarding Change in Investment Policy** 

**Supplement dated June 24, 2026 to the Fund's Prospectus dated September 28, 2023, as supplemented from time to time (the "Prospectus"); and to the Statement of Additional Information dated September 28, 2023, as supplemented from time to time (the "SAI")** 

*On June 23, 2026, the Board of Trustees approved changes to the Fund's 80% investment policy. Effective August 28, 2026, the Fund invests, under normal circumstances, at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in corporate debt obligations of varying maturities and/or income-producing investments, which may include those of non-corporate issuers.* 

*Accordingly, effective August 28, 2026, the Fund's Prospectus and SAI are revised as shown below.* 

***Prospectus***

*The first sentence of the first paragraph under the "Portfolio Contents" section on the cover page of the Fund's Prospectus is deleted and replaced with the following:* 

The Fund invests, under normal circumstances, at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in corporate debt obligations of varying maturities and/or income-producing investments, which may include those of non-corporate issuers. Income-producing investments may include income-producing Fixed Income Instrument investments, dividend-paying equity securities, derivatives on either of the foregoing, derivatives providing exposure to other types of income-producing instruments, and any other instrument or arrangement that is structured to produce income, including any derivatives position that produces income or the sale of which produces a premium payment. "Fixed Income Instruments" include bonds, debt securities, bank loans and other similar instruments issued by various U.S. and non-U.S. public- or private-sector entities.

*The first sentence of the first paragraph under the "Prospectus Summary—Portfolio Contents" section of the Prospectus and the first sentence of the first paragraph under the "Portfolio Contents" section of the Prospectus are deleted and replaced with the following:* 

The Fund invests, under normal circumstances, at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in corporate debt obligations of varying maturities and/or income-producing investments, which may include those of non-corporate issuers (the "80% Policy").

*The last sentence of the third paragraph under the "Investment Objective and Policies" section of the Prospectus is deleted and replaced with the following:* 

The Fund may not change its 80% Policy unless it provides shareholders with at least 60 days' written notice of such change.

*The following is added as the new fourth sentence of the first paragraph under the "Prospectus Summary—Portfolio Contents" section of the Prospectus and the new fourth sentence of the first paragraph under the "Portfolio Contents" section of the Prospectus:* 

Income-producing investments may include income-producing Fixed Income Instrument investments, dividend-paying equity securities, derivatives on either of the foregoing, derivatives providing exposure to other types of income-producing instruments, and any other instrument or arrangement that is structured to produce income, including any derivatives position that produces income or the sale of which produces a premium payment.

------

*The following is added to the end of the first paragraph under the "Portfolio Contents—Derivatives" section of the Prospectus:* 

Derivative instruments used by the Fund are expected to be counted towards the Fund's 80% Policy to the extent they provide investment exposure to investments within that Policy or to one or more of the market risk factors associated with investments included in that Policy.

*The following is added as a new paragraph under the "Portfolio Contents" section of the Prospectus:* 

***Fixed Income Instruments***

"Fixed Income Instruments," as used generally in this prospectus, includes:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• securities issued or guaranteed by the U.S. Government, its agencies or government-sponsored enterprises
("U.S. Government Securities");

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• corporate debt securities of U.S. and non-U.S. issuers, including
convertible securities and corporate commercial paper;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• mortgage-backed and other asset-backed securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• inflation-indexed bonds issued both by governments and corporations;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• structured notes, including hybrid or "indexed" securities and event-linked bonds;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• bank capital and trust preferred securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• loans, including participations in and assignments thereof;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• delayed draw and delayed funding loans and revolving credit facilities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• bank certificates of deposit, fixed time deposits and bankers' acceptances;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• repurchase agreements on Fixed Income Instruments and reverse repurchase agreements on Fixed Income
Instruments;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• debt securities issued by states or local governments and their agencies, authorities and other
government-sponsored enterprises;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• obligations of non-U.S. governments or their subdivisions, agencies
and government-sponsored enterprises; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• obligations of international agencies or supranational entities.

Securities issued by U.S. Government agencies or government-sponsored enterprises may not be guaranteed by the U.S. Treasury.

The Fund, to the extent permitted by the 1940 Act, the rules thereunder or any exemptive relief therefrom, may invest in derivatives based on Fixed Income Instruments.

***SAI***

*The ninth paragraph under the "INVESTMENT RESTRICTIONS—Other Information Regarding Investment Restrictions" section of the Fund's SAI is deleted and replaced with the following:* 

The Fund may not change its policy to invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in corporate debt obligations of varying maturities and/or income-producing investments, which may include those of non-corporate issuers (the "80% Policy"), unless it provides shareholders with at least 60 days' written notice of such change.

------

*The first sentence of the twelfth paragraph under the "INVESTMENT RESTRICTIONS—Other Information Regarding Investment Restrictions" section of the Fund's SAI is deleted and replaced with the following:* 

Except as otherwise required by applicable regulation, for purposes of its investment policies and restrictions, the Fund may value derivative instruments at market value, notional value or full exposure value (i.e., the sum of the notional amount for the contract plus the market value), or any combination of the foregoing (e.g., notional value for purposes of calculating the numerator and market value for purposes of calculating the denominator for compliance with a particular policy or restriction).

*The fourth sentence of the twelfth paragraph under the "INVESTMENT RESTRICTIONS—Other Information Regarding Investment Restrictions" section of the Fund's SAI is deleted.* 

**<u>Investors Should Retain This Supplement for Future Reference</u>**

PTY_SUPP1_062426