# EDGAR Filing Document

**Accession Number:** 0000701039
**File Stem:** 0000940394-23-000191
**Filing Date:** 2023-2
**Character Count:** 39491
**Document Hash:** ac1baa0d83304b4aac0f9996653087c0
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000940394-23-000191.hdr.sgml**: 20230201

**ACCESSION NUMBER**: 0000940394-23-000191

**CONFORMED SUBMISSION TYPE**: 497K

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20230201

**DATE AS OF CHANGE**: 20230131

**EFFECTIVENESS DATE**: 20230201

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** CALVERT FUND
- **CENTRAL INDEX KEY:** 0000701039
- **IRS NUMBER:** 526228948
- **STATE OF INCORPORATION:** MD
- **FISCAL YEAR END:** 0930

**FILING VALUES:**
- **FORM TYPE:** 497K
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 002-76510
- **FILM NUMBER:** 23573759

**BUSINESS ADDRESS:**
- **STREET 1:** 1825 CONNECTICUT AVENUE NW
- **STREET 2:** SUITE 400
- **CITY:** WASHINGTON
- **STATE:** DC
- **ZIP:** 20009
- **BUSINESS PHONE:** 8002256265

**MAIL ADDRESS:**
- **STREET 1:** 1825 CONNECTICUT AVENUE NW
- **STREET 2:** SUITE 400
- **CITY:** WASHINGTON
- **STATE:** DC
- **ZIP:** 20009

## Series and Classes Contracts Data

### Calvert Ultra-Short Duration Income Fund (Series ID: S000013508)

| Class ID   | Class Name                                       | Ticker Symbol   |
|:---|:---|:---|
| C000036621 | Class A                                          | CULAX           |
| C000139784 | Calvert Ultra-Short Duration Income Fund Class I | CULIX           |
| C000195935 | Class R6                                         | CULRX           |

![](cfcusdifsp_001.jpg)

Summary Prospectus dated February 1, 2023

**Calvert Ultra-Short Duration Income Fund**

Class / Ticker A / CULAX I / CULIX R6 / CULRX

**This Summary Prospectus is designed to provide investors with key fund information in a clear and concise format. Before you invest, you may want to review the Fund's Prospectus and Statement of Additional Information, which contain more information about the Fund and its risks. The Fund's Prospectus and Statement of Additional Information, both dated February 1, 2023, as may be amended or supplemented, are incorporated by reference into this Summary Prospectus. For free paper or electronic copies of the Fund's Prospectus, Statement of Additional Information, annual and semi-annual shareholder reports, and other information about the Fund, go to http://www.calvert.com/prospectus, email a request to Prospectusrequest@calvert.com, call 1-800-368-2745, or ask any financial advisor, bank, or broker-dealer who offers shares of the Fund. Unless otherwise noted, page number references refer to the current Prospectus for this Fund.**

**Investment Objective**

The Fund's investment objective is to seek to maximize income, to the extent consistent with preservation of capital, through investment in short-term bonds and income-producing securities.

**Fees and Expenses of the Fund**

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. Investors may also pay commissions or other fees to their financial intermediary when they buy and hold shares of the Fund, which are not reflected below.

---

| | | | |
|:---|:---|:---|:---|
| &nbsp;&nbsp;&nbsp;&nbsp;Shareholder Fees (fees paid directly from your investment) | &nbsp;&nbsp;Class A | &nbsp;&nbsp;Class I | &nbsp;&nbsp;Class R6 |
| &nbsp;&nbsp;&nbsp;&nbsp;Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price) |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Maximum Deferred Sales Charge (load) (as a percentage of the lower of net asset value at purchase or redemption) |  |  |  |

---

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| | | | |
|:---|:---|:---|:---|
| &nbsp;&nbsp;&nbsp;&nbsp;Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment) | &nbsp;&nbsp;Class A | &nbsp;&nbsp;Class I | &nbsp;&nbsp;Class R6 |
| &nbsp;&nbsp;&nbsp;&nbsp;Management Fees | &nbsp;&nbsp;0.38% | &nbsp;&nbsp;0.38% | &nbsp;&nbsp;0.38% |
| &nbsp;&nbsp;&nbsp;&nbsp;Distribution and Service (12b-1) Fees | &nbsp;&nbsp;0.25% |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Other Expenses | &nbsp;&nbsp;<u>0.12</u>% | &nbsp;&nbsp;<u>0.12</u>% | &nbsp;&nbsp;<u>0.08</u>% |
| &nbsp;&nbsp;&nbsp;&nbsp;Total Annual Fund Operating Expenses | &nbsp;&nbsp;0.75% | &nbsp;&nbsp;0.50% | &nbsp;&nbsp;0.46% |
| &nbsp;&nbsp;&nbsp;&nbsp;Less Fee Waiver and/or Expense Reimbursement <sup>(1)</sup> | &nbsp;&nbsp;<u>(0.03)</u>% | &nbsp;&nbsp;<u>(0.03)</u>% | &nbsp;&nbsp;<u>(0.03)</u>% |
| &nbsp;&nbsp;&nbsp;&nbsp;Total Annual Fund Operating Expenses after Fee Waiver and/or Expense Reimbursement | &nbsp;&nbsp;0.72% | &nbsp;&nbsp;0.47% | &nbsp;&nbsp;0.43% |

---

<sup>(1)</sup> Calvert Research and Management ("CRM") has agreed to reimburse the Fund's expenses to the extent that Total Annual Fund Operating Expenses exceed 0.72% for Class A shares, 0.47% for Class I shares and 0.43% for Class R6 shares. This expense reimbursement will continue through January 31, 2024. Any amendment to or termination of this reimbursement would require approval of the Board of Trustees. The expense reimbursement relates to ordinary operating expenses only and does not include expenses such as: brokerage commissions, acquired fund fees and expenses of unaffiliated funds, borrowing costs (including borrowing costs of any acquired funds), taxes or litigation expenses. Amounts reimbursed may be recouped by CRM during the same fiscal year to the extent actual expenses are less than any contractual expense cap in place during such year.

**Example.** This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year, that the operating expenses remain the same and that any expense reimbursement arrangement remains in place for the contractual period. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | 1 Year | 3 Years | 5 Years | 10 Years |
| Class A shares | $74 | $237 | $414 | $928 |
| Class I shares | $48 | $157 | $277 | $625 |
| Class R6 shares | $44 | $145 | $255 | $576 |

---

**Portfolio Turnover**

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" the portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 78% of the average value of its portfolio.

**Principal Investment Strategies**

The Fund seeks to achieve its investment objective by investing, under normal circumstances, at least 80% of its net assets (including borrowings for investment purposes) in a portfolio of floating-rate securities (e.g., corporate floating-rate securities) and securities with durations of less than or equal to one year ("80% Policy"). The Fund is not a money market fund and does not seek to maintain a stable net asset value.

Under normal circumstances, the Fund's average portfolio duration will be less than one year. The Fund generally defines ultra-short duration securities as those with durations of less than or equal to one year.

The Fund typically invests at least 85% of its net assets in investment grade, U.S. dollar-denominated debt securities, as assessed at the time of purchase. A debt security is considered investment grade when assigned a credit quality rating of BBB- or higher by S&P Global Ratings ("S&P") or an equivalent rating by another nationally recognized statistical rating organization (''NRSRO"), including Moody's Investors Service or Fitch Ratings, or Kroll Bond Rating Agency, LLC for securitized debt instruments only (such as asset-backed securities ("ABS") and mortgage-backed securities ("MBS")) or if unrated, considered to be of comparable credit quality by the Fund's investment adviser. For purposes of rating restrictions, if securities are rated differently by two or more rating agencies, the highest rating is used.

The Fund invests principally in bonds issued by U.S. corporations, the U.S. Government or its agencies, and U.S. government-sponsored enterprises ("GSEs") such as the Federal National Mortgage Association ("FNMA") and the Federal Home Loan Mortgage Corporation ("FHLMC"). The Fund also may invest in trust preferred securities, money market instruments, taxable municipal obligations and loans.

The Fund may invest in ABS and MBS that represent interests in pools of mortgage loans (MBS) or other assets (ABS) assembled for sale to investors by various U.S. governmental agencies, government-related organizations and private issuers. MBS may include collateralized mortgage obligations ("CMOs") and commercial mortgage-backed securities ("CMBS").

Under normal circumstances, the Fund will invest in below-investment grade, high-yield debt instruments (commonly known as "junk bonds"), including distressed instruments that are in default. The Fund's investment in such instruments is limited to 15% of its net assets.

The Fund may also invest up to 25% of its net assets in foreign debt securities. Foreign debt securities include American Depositary Receipts ("ADRs"). The Fund may engage in forward foreign currency exchange contracts to seek to hedge against the decline in the value of currencies in which its portfolio holdings are denominated against the U.S. dollar. The Fund may also lend its securities.

Investment decisions for the Fund are made primarily on the basis of fundamental and quantitative research conducted by the investment adviser's research staff and consideration of the responsible investment criteria described below. Management of the Fund involves consideration of numerous factors (such as quality of business franchises, financial strength, management quality and security structural and collateral considerations). The portfolio managers may also use sector rotation and relative value strategies in their management of the Fund. The portfolio managers may sell a security when the investment adviser's valuation target is reached, the fundamentals of the investment change or to pursue more attractive investment options. A security will also be sold (in accordance with the investment adviser's guidelines and at a time and in a manner that is determined to be in the best interests of shareholders) if the investment adviser determines that the issuer does not operate in a manner consistent with the Fund's responsible investment criteria. The portfolio managers intend to focus on risk management and also seek to preserve capital to the extent consistent with the Fund's investment objective. The Fund intends to seek to manage investment risk by maintaining broad issuer and industry diversification among its holdings, and by utilizing fundamental analysis of risk/return characteristics in securities selection. The Fund seeks to manage duration and any hedging of interest rate risk through the purchase and sale of U.S. Treasury securities and related futures contracts (which are a type of derivative instrument).

Calvert Ultra-Short Duration Income Fund 2 Summary Prospectus dated February 1, 2023

**Responsible Investing.** The portfolio manager(s) seek to invest in companies that manage environmental, social and governance ("ESG") risk exposures adequately and that are not exposed to excessive ESG risk through their principal business activities. Companies are analyzed by the investment adviser's ESG analysts utilizing The Calvert Principles for Responsible Investment ("Principles"), a framework for considering ESG factors (a copy of which is included as an appendix to the Fund's Prospectus). Each company is evaluated relative to an appropriate peer group based on material ESG factors as determined by the investment adviser. Pursuant to the Principles, the investment adviser seeks to identify companies and other issuers that operate in a manner that is consistent with or promotes environmental sustainability and resource efficiency, equitable societies and respect for human rights, and accountable governance and transparency. The Fund generally invests in issuers that are believed by the investment adviser to operate in accordance with the Principles and may also invest in issuers that the investment adviser believes are likely to operate in accordance with the Principles pending the investment adviser's engagement activity with such issuer.

**Principal Risks**

**Market Risk.** The value of investments held by the Fund may increase or decrease in response to social, economic, political, financial, public health crises or other disruptive events (whether real, expected or perceived) in the U.S. and global markets and include events such as war, natural disasters, epidemics and pandemics, terrorism, conflicts and social unrest. These events may negatively impact broad segments of businesses and populations and may exacerbate pre-existing risks to the Fund. The frequency and magnitude of resulting changes in the value of the Fund's investments cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in reaction to changing market conditions. Monetary and/or fiscal actions taken by U.S. or foreign governments to stimulate or stabilize the global economy may not be effective and could lead to high market volatility. No active trading market may exist for certain investments held by the Fund, which may impair the ability of the Fund to sell or to realize the full value of such investments in the event of the need to liquidate such assets.

**Interest Rate Risk.** In general, the value of income securities will fluctuate based on changes in interest rates. The value of these securities is likely to increase when interest rates fall and decline when interest rates rise. Duration measures the time-weighted expected cash flows of a fixed-income security, while maturity refers to the amount of time until a fixed-income security matures. Generally, securities with longer durations or maturities are more sensitive to changes in interest rates than securities with shorter durations or maturities, causing them to be more volatile. Conversely, fixed-income securities with shorter durations or maturities will be less volatile but may provide lower returns than fixed-income securities with longer durations or maturities. Funds with shorter average durations (including the Fund) may own individual investments that have longer durations than the average duration of the Fund. The impact of interest rate changes is significantly less for floating-rate securities that have relatively short periodic rate resets (e.g., ninety days or less). In a rising interest rate environment, the duration of income securities that have the ability to be prepaid or called by the issuer may be extended. In a declining interest rate environment, the proceeds from prepaid or maturing instruments may have to be reinvested at a lower interest rate.

**LIBOR Risk.** The London Interbank Offered Rate or LIBOR is used throughout global banking and financial industries to determine interest rates for a variety of financial instruments (such as debt instruments and derivatives) and borrowing arrangements. The ICE Benchmark Administration Limited, the administrator of LIBOR, ceased publishing certain LIBOR settings on December 31, 2021, and is expected to cease publishing the remaining LIBOR settings on June 30, 2023. The Fund has exposure to LIBOR-based instruments. Although the transition process away from LIBOR has become increasingly well defined, the impact on certain debt securities, derivatives and other financial instruments that utilize LIBOR remains uncertain. The transition process may involve, among other things, increased volatility or illiquidity in markets for instruments that currently rely on LIBOR, such as floating-rate debt obligations. Any effects of the transition away from LIBOR and the adoption of alternative reference rates, as well as other unforeseen effects, could result in losses to the Fund, and such effects may occur prior to the anticipated discontinuation of the remaining LIBOR settings in 2023. Furthermore, the risks associated with the discontinuation of LIBOR and transition to replacement rates may be exacerbated if an orderly transition to an alternative reference rate is not completed in a timely manner.

**Credit Risk.** Investments in debt securities (including bonds) and loans (referred to below as "debt instruments") are subject to the risk of non-payment of scheduled principal and interest. Changes in economic conditions or other circumstances may reduce the capacity of the party obligated to make principal and interest payments on such instruments and may lead to defaults. Such non-payments and defaults may reduce the value of Fund shares and income distributions. The value of debt instruments also may decline because of concerns about the issuer's ability to make principal and interest payments. In addition, the credit ratings of debt instruments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments deteriorates. In the event of bankruptcy of the issuer of a debt instrument, the Fund could experience delays or limitations with respect to its ability to realize the benefits of any collateral securing the instrument. In order to enforce its rights in the event of a default, bankruptcy or similar situation, the Fund may be required to retain legal or similar counsel, which may increase the Fund's operating expenses and adversely affect net asset value.

Calvert Ultra-Short Duration Income Fund 3 Summary Prospectus dated February 1, 2023

**Mortgage- and Asset-Backed Securities Risk.** Mortgage- and asset-backed securities represent interests in "pools" of commercial or residential mortgages or other assets, including consumer loans or receivables. Movements in interest rates (both increases and decreases) may quickly and significantly reduce the value of certain types of mortgage- and asset-backed securities. Although certain mortgage- and asset-backed securities are guaranteed as to timely payment of interest and principal by a government entity, the market price for such securities is not guaranteed and will fluctuate. The purchase of mortgage- and asset-backed securities issued by non-government entities may entail greater risk than such securities that are issued or guaranteed by a government entity. Mortgage- and asset-backed securities issued by non-government entities may offer higher yields than those issued by government entities, but may also be subject to greater volatility than government issues and can also be subject to greater credit risk and the risk of default on the underlying mortgages or other assets. Investments in mortgage- and asset-backed securities are subject to both extension risk, where borrowers pay off their debt obligations more slowly in times of rising interest rates, and prepayment risk, where borrowers pay off their debt obligations sooner than expected in times of declining interest rates.

**U.S. Government Securities Risk.** Although certain U.S. Government-sponsored agencies (such as the Federal Home Loan Mortgage Corporation and the Federal National Mortgage Association) may be chartered or sponsored by acts of Congress, their securities are neither issued nor guaranteed by the U.S. Treasury. U.S. Treasury securities generally have a lower return than other obligations because of their higher credit quality and market liquidity.

**Convertible and Other Hybrid Securities Risk.** Convertible and other hybrid securities (including preferred and convertible instruments) generally possess certain characteristics of both equity and debt securities. In addition to risks associated with investing in income securities, such as interest rate and credit risks, hybrid securities may be subject to issuer-specific and market risks generally applicable to equity securities. Convertible securities may also react to changes in the value of the common stock into which they convert, and are thus subject to equity investing and market risks. A convertible security may be converted at an inopportune time, which may decrease the Fund's return.

**Money Market Instrument Risk.** Money market instruments may be adversely affected by market and economic events, such as a sharp rise in prevailing short-term interest rates; adverse developments in the banking industry, which issues or guarantees many money market instruments; adverse economic, political or other developments affecting issuers of money market instruments; changes in the credit quality of issuers; and default by a counterparty.

**Preferred Stock Risk.** Although preferred stocks represent an ownership interest in an issuer, preferred stocks generally do not have voting rights or have limited voting rights and have economic characteristics similar to fixed-income securities. Preferred stocks are subject to issuer-specific risks generally applicable to equity securities and credit and interest rate risks generally applicable to fixed-income securities. The value of preferred stock generally declines when interest rates rise and may react more significantly than bonds and other debt instruments to actual or perceived changes in the company's financial condition or prospects.

**Municipal Obligations Risk.** The amount of public information available about municipal obligations is generally less than for corporate equities or bonds, meaning that the investment performance of municipal obligations may be more dependent on the analytical abilities of the investment adviser than stock or corporate bond investments. The secondary market for municipal obligations also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund's ability to sell its municipal obligations at attractive prices. The differences between the price at which an obligation can be purchased and the price at which it can be sold may widen during periods of market distress. Less liquid obligations can become more difficult to value and be subject to erratic price movements. The increased presence of non-traditional participants (such as proprietary trading desks of investment banks and hedge funds) or the absence of traditional participants (such as individuals, insurance companies, banks and life insurance companies) in the municipal markets may lead to greater volatility in the markets because non-traditional participants may trade more frequently or in greater volume.

**Additional Risks of Loans.** Loans are traded in a private, unregulated inter-dealer or inter-bank resale market and are generally subject to contractual restrictions that must be satisfied before a loan can be bought or sold. These restrictions may impede the Fund's ability to buy or sell loans (thus affecting their liquidity) and may negatively impact the transaction price. See also "Market Risk" above. It also may take longer than seven days for transactions in loans to settle. Due to the possibility of an extended loan settlement process, the Fund may hold cash, sell investments or temporarily borrow from banks or other lenders to meet short-term liquidity needs, such as to satisfy redemption requests from Fund shareholders. The types of covenants included in loan agreements generally vary depending on market conditions, the creditworthiness of the issuer, the nature of the collateral securing the loan and possibly other factors. Loans with fewer covenants that restrict activities of the borrower may provide the borrower with more flexibility to take actions that may be detrimental to the loan holders and provide fewer investor protections in the event of such actions or if covenants are breached. The Fund may experience relatively greater realized or unrealized losses or delays and expense in enforcing its rights with respect to loans with fewer restrictive covenants. Loans to entities located outside of the U.S. may have substantially different lender protections and covenants as compared to loans to U.S. entities and may involve greater risks. The Fund

Calvert Ultra-Short Duration Income Fund 4 Summary Prospectus dated February 1, 2023

may have difficulties and incur expense enforcing its rights with respect to non-U.S. loans and such loans could be subject to bankruptcy laws that are materially different than in the U.S. Loans may be structured such that they are not securities under securities law, and in the event of fraud or misrepresentation by a borrower, lenders may not have the protection of the anti-fraud provisions of the federal securities laws. Loans are also subject to risks associated with other types of income investments, including credit risk and risks of lower rated investments.

**Lower Rated Investments Risk.** Investments rated below investment grade and comparable unrated investments (sometimes referred to as "junk") have speculative characteristics because of the credit risk associated with their issuers. Changes in economic conditions or other circumstances typically have a greater effect on the ability of issuers of lower rated investments to make principal and interest payments than they do on issuers of higher rated investments. An economic downturn generally leads to a higher non-payment rate, and a lower rated investment may lose significant value before a default occurs. Lower rated investments typically are subject to greater price volatility and illiquidity than higher rated investments.

**Foreign Investment Risk.** Foreign investments can be adversely affected by political, economic and market developments abroad, including the imposition of economic and other sanctions by the United States or another country against a particular country or countries, organizations, entities and/or individuals. There may be less publicly available information about foreign issuers because they may not be subject to reporting practices, requirements or regulations comparable to those to which United States companies are subject. Adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. Foreign markets may be smaller, less liquid and more volatile than the major markets in the United States and, as a result, Fund share values may be more volatile. Trading in foreign markets typically involves higher expense than trading in the United States. The Fund may have difficulties enforcing its legal or contractual rights in a foreign country. Depositary receipts are subject to many of the risks associated with investing directly in foreign instruments.

**Currency Risk.** Exchange rates for currencies fluctuate daily. The value of foreign investments may be affected favorably or unfavorably by changes in currency exchange rates in relation to the U.S. dollar. Currency markets generally are not as regulated as securities markets and currency transactions are subject to settlement, custodial and other operational risks.

**Restricted Securities Risk.** Unless registered for sale to the public under applicable federal securities law, restricted securities can be sold only in private transactions to qualified purchasers pursuant to an exemption from registration. The sale price realized from a private transaction could be less than the Fund's purchase price for the restricted security. It may be difficult to identify a qualified purchaser for a restricted security held by the Fund and such security could be deemed illiquid. It may also be more difficult to value such securities.

**Liquidity Risk.** The Fund is exposed to liquidity risk when trading volume, lack of a market maker or trading partner, large position size, market conditions, or legal restrictions impair its ability to sell particular investments or to sell them at advantageous market prices. Consequently, the Fund may have to accept a lower price to sell an investment or continue to hold it or keep the position open, sell other investments to raise cash or abandon an investment opportunity, any of which could have a negative effect on the Fund's performance. These effects may be exacerbated during times of financial or political stress.

**Derivatives Risk.** The Fund's exposure to derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other investments. The use of derivatives can lead to losses because of adverse movements in the price or value of the security, instrument, index, currency, commodity, economic indicator or event underlying a derivative ("reference instrument"), due to failure of a counterparty or due to tax or regulatory constraints. Derivatives may create leverage in the Fund, which represents a non-cash exposure to the underlying reference instrument. Leverage can increase both the risk and return potential of the Fund. Derivatives risk may be more significant when derivatives are used to enhance return or as a substitute for a cash investment position, rather than solely to hedge the risk of a position held by the Fund. Use of derivatives involves the exercise of specialized skill and judgment, and a transaction may be unsuccessful in whole or in part because of market behavior or unexpected events. Changes in the value of a derivative (including one used for hedging) may not correlate perfectly with the underlying reference instrument. Derivative instruments traded in over-the-counter markets may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the value of the underlying reference instrument. If a derivative's counterparty is unable to honor its commitments, the value of Fund shares may decline and the Fund could experience delays in (or be unable to achieve) the return of collateral or other assets held by the counterparty. The loss on derivative transactions may substantially exceed the initial investment. A derivative investment also involves the risks relating to the reference instrument underlying the investment.

**Securities Lending Risk.** Securities lending involves a possible delay in recovery of the loaned securities or a possible loss of rights in the collateral if the borrower fails financially. The Fund could also lose money if the value of the collateral decreases.

Calvert Ultra-Short Duration Income Fund 5 Summary Prospectus dated February 1, 2023

**Responsible Investing Risk.** Investing primarily in responsible investments carries the risk that, under certain market conditions, the Fund may underperform funds that do not utilize a responsible investment strategy. The application of responsible investment criteria may affect the Fund's exposure to certain sectors or types of investments, and may impact the Fund's relative investment performance depending on whether such sectors or investments are in or out of favor in the market. An investment's ESG performance or the investment adviser's assessment of such performance may change over time, which could cause the Fund to temporarily hold securities that do not comply with the Fund's responsible investment criteria. In evaluating an investment, the investment adviser is dependent upon information and data that may be incomplete, inaccurate or unavailable, which could adversely affect the analysis of the ESG factors relevant to a particular investment. Successful application of the Fund's responsible investment strategy will depend on the investment adviser's skill in properly identifying and analyzing material ESG issues.

**Risks Associated with Active Management.** The success of the Fund's investment strategy depends on portfolio management's successful application of analytical skills and investment judgment. Active management involves subjective decisions and there is no guarantee that such decisions will produce the desired results or expected returns.

**General Fund Investing Risks.** The Fund is not a complete investment program and there is no guarantee that the Fund will achieve its investment objective. It is possible to lose money by investing in the Fund. The Fund is not suited for short-term trading, and investors in the Fund should be able to tolerate potentially sharp declines in value over time. Purchase and redemption activities by Fund shareholders may impact the management of the Fund and its ability to achieve its investment objective(s). In addition, the redemption by one or more large shareholders or groups of shareholders of their holdings in the Fund could have an adverse impact on the remaining shareholders in the Fund. The Fund relies on various service providers, including the investment adviser, in its operations and is susceptible to operational, information security and related events (such as public health crises, cyber or hacking attacks) that may affect the service providers or the services that they provide to the Fund. An investment in the Fund is not a deposit in a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

**Performance**

The following bar chart and table provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and how the Fund's average annual returns over time compare with those of a broad-based securities market index. The returns in the bar chart are for Class A shares. Past performance (both before and after taxes) is not necessarily an indication of how the Fund will perform in the future.

CRM became the investment adviser to the Fund on December 31, 2016. Performance reflected prior to such date is that of the Fund's former investment adviser. Performance has been recalculated following a share split that occurred at the close of business on June 15, 2018. The Fund's performance reflects the effects of expense reductions. Absent these reductions, performance would have been lower. Updated Fund performance information can be obtained by visiting www.calvert.com.

![](cfcusdifsp_002.jpg)

For the ten years ended December 31, 2022, the highest quarterly total return for Class A was 3.91% for the quarter ended June 30, 2020 and the lowest quarterly return was -4.35% for the quarter ended March 31, 2020.

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| | | | |
|:---|:---|:---|:---|
| &nbsp;&nbsp;&nbsp;&nbsp;Average Annual Total Returns as of December 31, 2022 | &nbsp;&nbsp;One Year | &nbsp;&nbsp;Five Years | &nbsp;&nbsp;Ten Years |
| &nbsp;&nbsp;&nbsp;&nbsp;Class A Return Before Taxes | &nbsp;&nbsp;-0.27% | &nbsp;&nbsp;1.05% | &nbsp;&nbsp;1.02% |
| &nbsp;&nbsp;&nbsp;&nbsp;Class A Return After Taxes on Distributions | &nbsp;&nbsp;-0.97% | &nbsp;&nbsp;0.38% | &nbsp;&nbsp;0.49% |
| &nbsp;&nbsp;&nbsp;&nbsp;Class A Return After Taxes on Distributions and Sale of Class A Shares | &nbsp;&nbsp;-0.16% | &nbsp;&nbsp;0.49% | &nbsp;&nbsp;0.54% |
| &nbsp;&nbsp;&nbsp;&nbsp;Class I Return Before Taxes | &nbsp;&nbsp;-0.02% | &nbsp;&nbsp;1.30% | &nbsp;&nbsp;1.27% |
| &nbsp;&nbsp;&nbsp;&nbsp;Class R6 Return Before Taxes | &nbsp;&nbsp;0.12% | &nbsp;&nbsp;1.34% | &nbsp;&nbsp;1.30% |
| &nbsp;&nbsp;&nbsp;&nbsp;Bloomberg 9-12 Months Short Treasury Index (reflects no deduction for fees, expenses or taxes) | &nbsp;&nbsp;-0.40% | &nbsp;&nbsp;1.21% | &nbsp;&nbsp;0.81% |

---

Calvert Ultra-Short Duration Income Fund 6 Summary Prospectus dated February 1, 2023

These returns reflect the elimination of the Class A front-end sales charge effective August 19, 2019. The Class R6 performance shown above for the period prior to October 3, 2017 (commencement of operations) is the performance of Class I shares at net asset value without adjustment for any differences in expenses of the two classes and the Class I performance shown above for the period prior to January 31, 2014 (commencement of operations) is the performance of Class A shares at net asset value without adjustment for any differences in expenses of the two classes. If adjusted for such differences, returns would be different. Investors cannot invest directly in an Index.

After-tax returns are calculated using the highest historical individual federal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on a shareholder's tax situation and the actual characterization of distributions, and may differ from those shown. After-tax returns are not relevant to shareholders who hold shares in tax-deferred accounts or to shares held by non-taxable entities. After-tax returns for other Classes of shares will vary from the after-tax returns presented for Class A shares. Return After Taxes on Distributions for a period may be the same as Return Before Taxes for that period because no taxable distributions were made during that period. Also, Return After Taxes on Distributions and Sale of Fund Shares for a period may be greater than or equal to Return Before Taxes and/or Return After Taxes on Distributions for the same period because of losses realized on the sale of Fund shares.

**Management**

**Investment Adviser.** Calvert Research and Management ("CRM" or the "Adviser").

**Portfolio Managers**

Vishal Khanduja, CFA, Vice President of CRM, has managed the Fund since July 2012.

Brian S. Ellis, CFA, Vice President of CRM, has managed the Fund since March 2015.

**Purchase and Sale of Fund Shares**

You may purchase, redeem or exchange Fund shares on any business day, which is any day the New York Stock Exchange is open for business. You may purchase, redeem or exchange Fund shares either through your financial intermediary or directly from the Fund either by writing to the Fund, P.O. Box 219544, Kansas City, MO 64121-9544, or by calling 1-800-368-2745. The minimum initial purchase or exchange into the Fund is $1,000 for Class A, $1,000,000 for Class I and $5,000,000 for Class R6 (waived in certain circumstances). There is no minimum for subsequent investments.

**Tax Information**

If your shares are held in a taxable account, the Fund's distributions will be taxed to you as ordinary income and/or capital gains, unless you are exempt from taxation. If your shares are held in a tax-advantaged account, you will generally be taxed only upon withdrawals from the account.

**Payments to Broker-Dealers and Other Financial Intermediaries**

If you purchase the Fund's shares through a broker-dealer or other financial intermediary (such as a bank) (collectively, "financial intermediaries"), the Fund, its principal underwriter and its affiliates may pay the financial intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the financial intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary's website for more information.

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Calvert Ultra-Short Duration Income Fund 7 Summary Prospectus dated February 1, 2023