# EDGAR Filing Document

**Accession Number:** 0000002110
**File Stem:** 0001193125-26-172181
**Filing Date:** 2026-4
**Character Count:** 48546
**Document Hash:** 6593de51ae9b8e7819c29f10bc253561
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-172181.hdr.sgml**: 20260423

**ACCESSION NUMBER**: 0001193125-26-172181

**CONFORMED SUBMISSION TYPE**: 497K

**PUBLIC DOCUMENT COUNT**: 5

**FILED AS OF DATE**: 20260423

**DATE AS OF CHANGE**: 20260423

**EFFECTIVENESS DATE**: 20260423

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** COLUMBIA ACORN TRUST
- **CENTRAL INDEX KEY:** 0000002110

**ORGANIZATION NAME:**
- **EIN:** 362692100
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 497K
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 002-34223
- **FILM NUMBER:** 26886083

**BUSINESS ADDRESS:**
- **STREET 1:** 71 S. WACKER DRIVE, SUITE 2500
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606
- **BUSINESS PHONE:** 3126349200

**MAIL ADDRESS:**
- **STREET 1:** 71 S. WACKER DRIVE, SUITE 2500
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** LIBERTY ACORN TRUST
- **DATE OF NAME CHANGE:** 20010424

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** ACORN INVESTMENT TRUST
- **DATE OF NAME CHANGE:** 19940204

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** ACORN FUND INC
- **DATE OF NAME CHANGE:** 19920703

## Series and Classes Contracts Data

### Columbia Thermostat Fund (Series ID: S000009189)

| Class ID   | Class Name                                     | Ticker Symbol   |
|:---|:---|:---|
| C000024974 | Columbia Thermostat Fund Class A               | CTFAX           |
| C000024976 | Columbia Thermostat Fund Class C               | CTFDX           |
| C000024977 | Columbia Thermostat Fund Institutional Class   | COTZX           |
| C000122750 | Columbia Thermostat Fund Institutional 2 Class | CQTRX           |
| C000122751 | Columbia Thermostat Fund Institutional 3 Class | CYYYX           |
| C000251062 | Columbia Thermostat Class S                    | COTDX           |

![](g607054img26c3a0191.gif)

Columbia Thermostat Fund<sup>SM</sup>

**Summary Prospectus**

May 1, 2026 <br>

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| | |
|:---|:---|
| **Class** | **Ticker Symbol** |
| A | CTFAX |
| C | CTFDX |
| Institutional (Class Inst) | COTZX |
| Institutional 2 (Class Inst2) | CQTRX |
| Institutional 3 (Class Inst3) | CYYYX |
| S | COTDX |

---

Before you invest, you may want to review the Fund's prospectus, which contains more information about the Fund and its risks. You can find the Fund's prospectus, reports to shareholders, statement of additional information and other information about the Fund online at https://www.columbiathreadneedleus.com/resources/literature. If you hold your Fund shares through a financial intermediary (such as a broker-dealer or bank), you can get this information at no cost by contacting that financial intermediary. If you hold your Fund shares directly with the Fund, you can get this information at no cost by calling 800.345.6611 or by sending an email to serviceinquiries@columbiathreadneedle.com. This Summary Prospectus incorporates by reference the Fund's prospectus, dated May 1, 2026, and current Statement of Additional Information.

As with all mutual funds, the Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.

![](g607054fdic_2025.gif)

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**Investment Objective**

Columbia Thermostat Fund<sup>SM</sup> (the Fund) seeks long-term capital appreciation.

**Fees and Expenses of the Fund**

This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. **You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.** You may qualify for sales charge discounts if you and members of your immediate family invest, or agree to invest in the future, at least $50,000 in certain classes of shares of eligible funds distributed by Columbia Management Investment Distributors, Inc. (the Distributor). More information is available about these and other sales charge discounts and waivers from your financial intermediary, and can be found in the *Choosing a Share Class* section beginning on page 33 of the Fund's prospectus, in *Appendix A* to the prospectus beginning on page A-1 and in Appendix S to the Statement of Additional Information (SAI) under *Sales Charge Waivers* beginning on page S-1.

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| | | | |
|:---|:---|:---|:---|
| **Shareholder Fees (fees paid directly from your investment)** | **Shareholder Fees (fees paid directly from your investment)** | **Shareholder Fees (fees paid directly from your investment)** | **Shareholder Fees (fees paid directly from your investment)** |
|  | **Class A** | **Class C** | **Classes Inst, Inst2,** <br> **Inst3, and S**<br>|
| Maximum sales charge (load) imposed on purchases (as a % of offering price) | 5.75<br> %<br>|  |  |
| &nbsp;&nbsp; Maximum deferred sales charge (load) imposed on redemptions (as a % of the lower of the <br> original purchase price or current net asset value)<br>| 1.00 %<sup>(a)</sup><br>| 1.00 %<sup>(b)</sup><br>|  |

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

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| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
| **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)** | **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)** | **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)** | **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)** | **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)** | **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)** | **Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)** |
|  | **Class A** | **Class C** | **Class Inst** | **Class Inst2** | **Class Inst3** | **Class S** |
| Management fees | 0.10<br> %<br>| 0.10<br> %<br>| 0.10<br> %<br>| 0.10<br> %<br>| 0.10<br> %<br>| 0.10<br> %<br>|
| Distribution and/or service (12b-1) fees | 0.25<br> %<br>| 1.00<br> %<br>| 0.00<br> %<br>| 0.00<br> %<br>| 0.00<br> %<br>| 0.00<br> %<br>|
| Other expenses<sup>(c)</sup> <br>| 0.13<br> %<br>| 0.13<br> %<br>| 0.13<br> %<br>| 0.09<br> %<br>| 0.05<br> %<br>| 0.13<br> %<br>|
| Acquired fund fees and expenses | 0.39<br> %<br>| 0.39<br> %<br>| 0.39<br> %<br>| 0.39<br> %<br>| 0.39<br> %<br>| 0.39<br> %<br>|
| **Total annual Fund operating expenses**<sup>(d)</sup> | 0.87<br> %<br>| 1.62<br> %<br>| 0.62<br> %<br>| 0.58<br> %<br>| 0.54<br> %<br>| 0.62<br> %<br>|

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(a) This charge is imposed on certain investments of between $1 million and $50 million redeemed within 18 months after purchase, as follows: 1.00% if redeemed within 12 months after purchase, and 0.50% if redeemed more than 12, but less than 18, months after purchase, with certain limited exceptions.

(b) This charge applies to redemptions within 12 months after purchase, with certain limited exceptions.

(c) Other expenses have been restated to reflect current fees paid by the Fund.

(d) "Total annual Fund operating expenses" include acquired fund (Portfolio Fund) fees and expenses (expenses the Fund incurs indirectly through its investments in other funds) and may be higher than the ratio of expenses to average net assets shown in the *Financial Highlights* section of this prospectus because the ratio of expenses to average net assets does not include Portfolio Fund (acquired fund) fees and expenses.

**Example**

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

<sup>■</sup>

you invest $10,000 in the applicable class of Fund shares for the periods indicated,

<sup>■</sup>

your investment has a 5% return each year, and

<sup>■</sup>

the Fund's total annual operating expenses remain the same as shown in the *Annual Fund Operating Expenses* table above.

*Class C shares' 10-year cost examples below reflect the Class C shares' 8-year conversion policy.* Although your actual costs may be higher or lower, based on the assumptions listed above, your costs would be:

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| | | | | |
|:---|:---|:---|:---|:---|
|  | **1 year** | **3 years** | **5 years** | **10 years** |
| **Class A** (whether or not shares are redeemed) | &nbsp;&nbsp;&nbsp;&nbsp; $659 | &nbsp;&nbsp;&nbsp;&nbsp; $837 | &nbsp;&nbsp;&nbsp;&nbsp; $1029 | &nbsp;&nbsp;&nbsp;&nbsp; $1586 |
| **Class C** (assuming redemption of all shares at the end of the period) | &nbsp;&nbsp;&nbsp;&nbsp; $265 | &nbsp;&nbsp;&nbsp;&nbsp; $511 | &nbsp;&nbsp;&nbsp;&nbsp; $881 | &nbsp;&nbsp;&nbsp;&nbsp; $1721 |
| **Class C** (assuming no redemption of shares) | &nbsp;&nbsp;&nbsp;&nbsp; $165 | &nbsp;&nbsp;&nbsp;&nbsp; $511 | &nbsp;&nbsp;&nbsp;&nbsp; $881 | &nbsp;&nbsp;&nbsp;&nbsp; $1721 |
| **Class Inst** (whether or not shares are redeemed) | &nbsp;&nbsp;&nbsp;&nbsp; $63 | &nbsp;&nbsp;&nbsp;&nbsp; $199 | &nbsp;&nbsp;&nbsp;&nbsp; $346 | &nbsp;&nbsp;&nbsp;&nbsp; $774 |
| **Class Inst2** (whether or not shares are redeemed) | &nbsp;&nbsp;&nbsp;&nbsp; $59 | &nbsp;&nbsp;&nbsp;&nbsp; $186 | &nbsp;&nbsp;&nbsp;&nbsp; $324 | &nbsp;&nbsp;&nbsp;&nbsp; $726 |
| **Class Inst3** (whether or not shares are redeemed) | &nbsp;&nbsp;&nbsp;&nbsp; $55 | &nbsp;&nbsp;&nbsp;&nbsp; $173 | &nbsp;&nbsp;&nbsp;&nbsp; $302 | &nbsp;&nbsp;&nbsp;&nbsp; $677 |

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Columbia Thermostat Fund<sup>SM</sup>

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| | | | | |
|:---|:---|:---|:---|:---|
|  | **1 year** | **3 years** | **5 years** | **10 years** |
| **Class S** (whether or not shares are redeemed) | &nbsp;&nbsp;&nbsp;&nbsp; $63 | &nbsp;&nbsp;&nbsp;&nbsp; $199 | &nbsp;&nbsp;&nbsp;&nbsp; $346 | &nbsp;&nbsp;&nbsp;&nbsp; $774 |

---

**Portfolio Turnover**

The Fund and the underlying funds in which the Fund invests pay transaction costs, such as commissions, when they buy and sell securities (or "turn over" their portfolios). The Fund will indirectly bear the expenses associated with portfolio turnover of these underlying funds. A high portfolio turnover rate may indicate higher transaction costs. 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 84% of the average value of its portfolio.

**Principal Investment Strategies**

The Fund is primarily managed as a fund that invests in other funds (i.e., a "fund-of-funds") that seeks to achieve its investment objective by investing its assets among a selected group of underlying stock and bond mutual funds and exchanged-traded funds (ETFs) for which Columbia Management Investment Advisers, LLC, the Fund's investment adviser (the Investment Manager), or its affiliates serves as investment adviser or principal underwriter (collectively, the Portfolio Funds). Under normal circumstances, the Fund allocates at least 95% of its net assets (stock/bond assets) among the Portfolio Funds according to an asset allocation table based on the current level of the Standard & Poor's (S&P) 500<sup>®</sup> Index.

Generally, the Fund's allocation to stock funds increases as the S&P 500<sup>®</sup> Index declines and decreases as the S&P 500<sup>®</sup> Index rises. When the S&P 500<sup>®</sup> Index goes up in relation to trading range bands that are predetermined by the Investment Manager, the Fund sells a portion of its stock Portfolio Funds and invests more in the bond Portfolio Funds, and when the S&P 500<sup>®</sup> Index goes down in relation to the predetermined bands, the Fund increases its investment in the stock Portfolio Funds. Under normal circumstances, the Fund may invest up to 5% of net assets plus any cash received that day in cash, high quality short-term paper and government securities.

Although many asset allocation funds follow a basic approach of moving assets from stocks to bonds when the equity market goes up, and from bonds to stocks when the equity market goes down, some are run by investment managers who allocate fund assets by making subjective decisions based on complicated economic and financial models and complex graphs of market behavior. By contrast, the day-to-day investment decisions for the Fund are made according to a single predetermined allocation table. The temperature in your house is run by a single rule: your thermostat turns on the furnace if your house is too cold or turns on the air conditioner if your house is too warm. This Fund works the same way, so it is named Columbia Thermostat Fund.

Just as a thermostat may be set at different ranges for different seasons, the structure and allocation ranges of the Fund's asset allocation table may be changed from time to time between two forms, based on the Investment Manager's determination of whether it expects the equity market to be moving over the next year in a side-ways or non-directional pattern, which the Investment Manager terms an "expensive" market, or to be trending upward, which the Investment Manager terms a "normal" market. The Investment Manager's process and methodology for determining whether the current market is "expensive" or "normal" and the structure of each form of allocation table are described in more detail in the *Principal Investment Strategies* section of the Fund's statutory prospectus. Such determination will be made on at least an annual basis and will be reflected in the asset allocation table disclosed in the Fund's statutory prospectus. In general, the two different forms of allocation table are intended to maximize the capture of value under the two different sets of market conditions.

The Fund's current form of asset allocation table, which is set forth in the *Principal Investment Strategies* section of the Fund's statutory prospectus, has been in place since the Fund's inception, except for the period from May 1, 2020 through April 30, 2021. The current form of asset allocation table reflects the Investment Manager's determination that the equity market is currently "expensive." The "expensive" form of table may result in equity investment allocations as low as 10% or as high as 90% of Fund assets. The Investment Manager evaluates the appropriate form of asset allocation table and updates the S&P 500<sup>®</sup> Index trading range bands within the table at least annually. From May 1, 2020 through April 30, 2021, the form of asset allocation table in place for the Fund reflected the Investment Manager's determination that the equity market was "normal." With the "normal" form of table, the Fund's equity investment allocations could be no less than 50% of Fund assets.

The Investment Manager chooses the Portfolio Funds to be generally consistent with the composition of the Fund's primary stock and bond benchmarks and to allow the Fund to participate in strategies the Investment Manager believes can provide additional return due to active management.

Columbia Thermostat Fund<sup>SM</sup>

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The stock and bond Portfolio Funds that the Fund currently uses in its "fund-of-funds" structure, and the current target percentage for each Portfolio Fund within the stock or bond asset class, is set forth in the *More Information – Principal Investment Strategies* section of the statutory prospectus for the Fund. The Investment Manager may substitute or add additional Portfolio Funds at any time, including funds introduced after the date of this prospectus.

See the *Appendix B: Portfolio Funds – Investment Objectives and Strategies* section of the Fund's statutory prospectus for information about the Portfolio Funds' investment objectives and principal investment strategies. Each of the Portfolio Funds is managed by the Investment Manager or its affiliates. The Fund does not pay any sales charges on its purchases of shares of the Portfolio Funds.

The Investment Manager will conduct the market state review at least annually prior to the annual updating of this prospectus, and may, in its discretion, assess the market state on an "emergency" basis and make any changes deemed necessary to reflect, for example, a very significant move in market levels or a structural change affecting the markets.

Any such "emergency" changes by the Investment Manager, which are expected to be infrequent, would be disclosed in this prospectus.

**Principal Risks**

An investment in the Fund involves risks, including **Allocation Risk**, **Market Risk**, **Fund-of-Funds Risk**, and **Changing Distribution Level Risk**, among others. Descriptions of these and other principal risks of investing in the Fund, including select risks related to the Portfolio Funds in which it invests, are provided below. More information about the Portfolio Funds, including their principal risks, is available in their prospectuses. A description of the principal risks associated with investment in these Portfolio Funds is included in the prospectus Appendix C. This prospectus is not an offer for any of the Portfolio Funds. *There is no assurance that the Fund will achieve its investment objective and you may lose money*. The value of the Fund's holdings may decline, and the Fund's net asset value (NAV) and share price may go down. An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. References in this section to "the Fund" also include the Portfolio Funds, as applicable. The significance of any specific risk to an investment in the Fund will vary over time depending on the composition of the Fund's portfolio, market conditions, and other factors. You should read all of the risk information below carefully, because any one or more of these risks may result in losses to the Fund.

**Active Management Risk.** Due to its active management, the Fund could underperform its benchmark index and/or other funds with similar investment objectives and/or strategies.

**Allocation Risk.** The Investment Manager uses an asset allocation strategy in pursuit of its investment objective, there is a risk that the Fund's allocation among asset classes or investments will cause the Fund's shares to lose value or cause the Fund to underperform other funds with similar investment objectives and/or strategies, or that the investments themselves will not produce the returns expected.

**Changing Distribution Level Risk.** The Fund normally expects to receive income which may include interest, dividends and/or capital gains, depending upon its investments. The distribution amounts paid by the Fund will vary and generally depend on the amount of income the Fund earns (less expenses) on its portfolio holdings, and capital gains or losses it recognizes. A decline in the Fund's income or net capital gains arising from its investments may reduce its distribution level.

**Credit Risk.** Credit risk is the risk that the value of loans or other debt instruments may decline if the issuer thereof defaults or otherwise becomes unable or unwilling, or is perceived to be unable or unwilling, to honor its financial obligations, such as making payments to the Fund when due. Various factors could affect the actual or perceived willingness or ability of the issuer to make timely interest or principal payments, including changes in the financial condition of the issuer or in general economic conditions. Credit rating agencies, such as S&P Global Ratings, Moody's Investors Service, Inc. (Moody's Ratings), Fitch Ratings, Inc. (Fitch), Morningstar DBRS (DBRS) and Kroll Bond Rating Agency, LLC (KBRA), assign credit ratings to certain debt instruments to indicate their credit risk. A rating downgrade by such agencies can negatively impact the value of such instruments. Lower-rated or unrated instruments held by the Fund may present increased credit risk as compared to higher-rated instruments. Non-investment grade debt instruments may be subject to greater price fluctuations and are more likely to experience a default than investment grade debt instruments and therefore may expose the Fund to increased credit risk. If the Fund purchases unrated instruments, or if the ratings of instruments held by the Fund are lowered after purchase, the Fund will depend on analysis of credit risk more heavily than usual.

**Derivatives Risk.** Derivatives may involve significant risks. Derivatives are financial instruments with a value in relation to, or derived from, the value of an underlying asset(s) or other reference, such as an index, rate or other economic indicator (each an underlying reference). Derivatives may include those that are privately placed or

Columbia Thermostat Fund<sup>SM</sup>

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otherwise exempt from SEC registration, including certain Rule 144A eligible securities. Derivatives could result in Fund losses if the underlying reference does not perform as anticipated. Use of derivatives is a highly specialized activity that can involve investment techniques, risks, and tax planning different from those associated with more traditional investment instruments. The Fund's derivatives strategy may not be successful, and use of certain derivatives could result in substantial, potentially unlimited, losses to the Fund regardless of the Fund's actual investment. A relatively small movement in the price, rate or other economic indicator associated with the underlying reference may result in substantial losses for the Fund. Derivatives may be more volatile than other types of investments. The value of derivatives may be influenced by a variety of factors, including national and international political and economic developments. Potential changes to the regulation of the derivatives markets may make derivatives more costly, may limit the market for derivatives, or may otherwise adversely affect the value or performance of derivatives. Derivatives can increase the Fund's risk exposure to underlying references and their attendant risks, such as credit risk, market risk, foreign currency risk and interest rate risk, while potentially exposing the Fund to correlation risk, counterparty risk, hedging risk, inflation risk, leverage risk, liquidity risk, pricing risk and volatility risk.

**Emerging Market Securities Risk.** Securities issued by foreign governments or companies in emerging market countries, such as China, Russia and certain countries in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid changes or developments in social, political, economic or other conditions. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity (i.e., lower trading volumes and less liquidity) than more developed countries. Emerging market securities tend to be more volatile, and may be more susceptible to market manipulation, than securities in more developed markets. Many emerging market countries are heavily dependent on international trade and have fewer trading partners, which makes them more sensitive to world commodity prices and economic downturns in other countries, and some have a higher risk of currency devaluations. Due to the differences in the nature and quality of financial information of issuers of emerging market securities, including auditing and financial reporting standards, financial information and disclosures about such issuers may be unavailable or, if made available, may be considerably less reliable than publicly available information about other foreign securities.

**Equity Securities Risk.** Equity securities may experience significant volatility. Such securities may fall sharply in response to adverse events affecting overall markets, a particular industry or sector, or an individual company's financial condition.

**Exchange-Traded Fund (ETF) Risk.** Investments in ETFs have unique characteristics, including, but not limited to, the expense structure and additional expenses associated with investing in ETFs. ETFs are subject to, among other risks, tracking risk and passive and, in some cases, active investment risk. In addition, shareholders bear both their proportionate share of the Fund's expenses, and indirectly the ETF's expenses, incurred through the Fund's ownership of the ETF. Because the expenses and costs of an underlying ETF are shared by its investors, redemptions by other investors in the ETF could result in decreased economies of scale and increased operating expenses for such ETF. The ETFs may not achieve their investment objective. The Fund, through its investment in ETFs, may not achieve its investment objective.

**Fixed Income Instruments Risk.** The Fund is subject to the general risks and considerations associated with investing in debt securities, including the risk that issuers will fail to make timely payments of principal or interest or default altogether. Lower-rated securities in which the Fund may invest may be more volatile and may decline more in price in response to negative issuer developments or general economic news than higher rated securities. In addition, as interest rates rise, the Fund's investments typically will lose value.

**Foreign Securities Risk.** Investments in or exposure to securities of foreign companies may involve heightened risks relative to investments in or exposure to securities of U.S. companies. Investing in securities of foreign companies subjects the Fund to the risks associated with an issuer's (and any of its related companies') country of organization and places of business operations, including risks related to political, regulatory, economic, social, diplomatic and other conditions or events (including, for example, military confrontations and actions, war, other conflicts, terrorism and disease/virus outbreaks and epidemics) occurring in the country or region, as well as risks associated with less developed custody and settlement practices. Foreign securities may be more volatile and less liquid than securities of U.S. companies and are subject to the risks associated with potential imposition of economic and other sanctions against a particular foreign country, its nationals or industries or businesses within the country. In addition, foreign governments may impose withholding or other taxes on the Fund's income, capital gains or proceeds from the disposition of foreign securities, which could reduce the Fund's return on such securities.

Columbia Thermostat Fund<sup>SM</sup>

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**Frequent Trading Risk.** The portfolio managers may actively and frequently trade investments in the Fund's portfolio to carry out its investment strategies. Frequent trading of investments increases the possibility that the Fund, as relevant, will realize taxable capital gains (including short-term capital gains, which are generally taxable to shareholders at higher rates than long-term capital gains for U.S. federal income tax purposes), which could reduce the Fund's after-tax return. Frequent trading can also mean higher brokerage and other transaction costs, which could reduce the Fund's return. The trading costs and tax effects associated with portfolio turnover may adversely affect the Fund's performance.

**Fund-of-Funds Risk.** Determinations regarding asset classes or Portfolio Funds and the Fund's allocations thereto may not successfully achieve the Fund's investment objective, in whole or in part. The selected Portfolio Funds' performance may be lower than the performance of the asset class they were selected to represent or may be lower than the performance of alternative Portfolio Funds that could have been selected to represent the asset class. The Fund also is exposed to the same risks as the Portfolio Funds in direct proportion to the allocation of its assets among the Portfolio Funds. By investing in a combination of Portfolio Funds, the Fund has exposure to the risks of many areas of the market. The ability of the Fund to realize its investment objective will depend, in large part, on the extent to which the Portfolio Funds realize their investment objectives. There is no guarantee that the Portfolio Funds will achieve their respective investment objectives. The performance of Portfolio Funds could be adversely affected if other entities that invest in the same Portfolio Funds make relatively large investments or redemptions in such Portfolio Funds. The Fund, and its shareholders, indirectly bear a portion of the expenses of any funds in which the Fund invests. Because the expenses and costs of each Portfolio Fund are shared by its investors, redemptions by other investors in a Portfolio Fund could result in decreased economies of scale and increased operating expenses for such fund. These transactions might also result in higher brokerage, tax or other costs for a Portfolio Fund. This risk may be particularly important when one investor owns a substantial portion of a Portfolio Fund. The Investment Manager may have potential conflicts of interest in selecting affiliated funds over unaffiliated funds for investment by the Fund, and may also face potential conflicts of interest in selecting affiliated funds, because the fees the Investment Manager receives from some Portfolio Funds may be higher than the fees paid by other Portfolio Funds. Columbia Thermostat Fund currently invests only in affiliated Portfolio Funds.

**Growth Securities Risk.** Growth securities typically trade at a higher multiple of earnings than other types of equity securities. Accordingly, the market values of growth securities may never reach their expected market value and may decline in price. In addition, growth securities, at times, may not perform as well as value securities or the stock market in general, and may be out of favor with investors for varying periods of time. Growth securities may also be sensitive to movements in interest rates.

**High-Yield Investments Risk.** Securities and other debt instruments held by the Fund that are rated below investment grade (commonly called "high-yield" or "junk" bonds) and unrated debt instruments of comparable quality expose the Fund to a greater risk of loss of principal and income than a fund that invests solely or primarily in investment grade debt instruments. In addition, these investments have greater price fluctuations, are less liquid and are more likely to experience a default than higher-rated debt instruments. High-yield debt instruments are considered to be predominantly speculative with respect to the issuer's capacity to pay interest and repay principal.

**Interest Rate Risk.** Interest rate risk is the risk of losses attributable to changes in interest rates. In general, if interest rates rise, the values of loans and other debt instruments tend to fall, and if interest rates fall, the values of loans and other debt instruments tend to rise. Changes in the value of a debt instrument usually will not affect the amount of income the Fund receives from it but will generally affect the value of your investment in the Fund. Changes in interest rates may also affect the liquidity of the Fund's investments in debt instruments. In general, the longer the maturity or duration of a debt instrument, the greater its sensitivity to changes in interest rates. For example, a three-year duration means a bond is expected to decrease in value by 3% if interest rates rise 1% and increase in value by 3% if interest rates fall 1%. Interest rate declines also may increase prepayments of debt obligations, which, in turn, would increase prepayment risk. The Fund is subject to the risk that the income generated by its investments may not keep pace with inflation. Actions by governments and central banking authorities can result in increases or decreases in interest rates. Higher periods of inflation could lead such authorities to raise interest rates. Such actions may negatively affect the value of debt instruments held by the Fund, resulting in a negative impact on the Fund's performance and NAV. Any interest rate increases could cause the value of the Fund's investments in debt instruments to decrease. Rising interest rates may prompt redemptions from the Fund, which may force the Fund to sell investments at a time when it is not advantageous to do so, which could result in losses.

**Issuer Risk.** An issuer in which the Fund invests or to which it has exposure may perform poorly or below expectations, and the value of its securities may therefore decline, which may negatively affect the Fund's performance. Underperformance of an issuer may be caused by poor management decisions, competitive pressures,

Columbia Thermostat Fund<sup>SM</sup>

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breakthroughs in technology, reliance on suppliers, labor problems or shortages, corporate restructurings, fraudulent disclosures, natural disasters, military confrontations and actions, war, other conflicts, terrorism, disease/virus outbreaks, epidemics or other events, conditions and factors which may impair the value of your investment in the Fund.

**Market Risk.** The Fund may incur losses due to declines in the value of one or more securities in which it invests. These declines may be due to factors affecting a particular issuer, or the result of, among other things, political, regulatory, market, economic or social developments affecting the relevant market(s) more generally. In addition, turbulence in financial markets and reduced liquidity in equity, credit and/or fixed income markets may negatively affect many issuers, which could adversely affect the Fund's ability to price or value hard-to-value assets in thinly traded and closed markets and could cause significant redemptions and operational challenges. Global economies and financial markets are increasingly interconnected, and conditions and events in one country, region or financial market may adversely impact issuers in a different country, region or financial market. These risks may be magnified if certain events or developments adversely interrupt the global supply chain; in these and other circumstances, such risks might affect companies worldwide. As a result, local, regional or global events such as terrorism, war, other conflicts, natural disasters, disease/virus outbreaks and epidemics or other public health issues, recessions, depressions or other events – or the potential for such events – could have a significant negative impact on global economic and market conditions.

**Sector Risk.** At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in an industry or related group of industries within one or more economic sectors. Companies in the same sector may be similarly affected by economic, regulatory, political or market events or conditions, which may make the Fund vulnerable to unfavorable developments in that industry, group of industries or economic sector.

**U.S. Government Obligations Risk.** While U.S. Treasury obligations are backed by the "full faith and credit" of the U.S. Government, such securities are nonetheless subject to credit risk (i.e., the risk that the U.S. Government may be, or be perceived to be, unable or unwilling to honor its financial obligations, such as making payments). Securities issued or guaranteed by federal agencies or authorities and U.S. Government-sponsored instrumentalities or enterprises may or may not be backed by the full faith and credit of the U.S. Government.

**Value Securities Risk.** Value securities are securities of companies that may have experienced, for example, adverse business, industry or other developments or may be subject to special risks that have caused the securities to be out of favor and, in turn, potentially undervalued. The market value of a portfolio security may not meet the perceived value assessment of that security as determined by the portfolio managers, or may decline in price, even though the securities are already believed to be undervalued by the portfolio managers. There is also a risk that it may take longer than expected for the value of these investments to rise to the perceived value as determined by the portfolio managers. In addition, value securities, at times, may not perform as well as growth securities or the stock market in general, and may be out of favor with investors for varying periods of time.

**Performance Information**

The following bar chart and table show you how the Fund has performed in the past, and can help you understand the risks of investing in the Fund. The bar chart shows how the Fund's Class A share performance (without sales charges) has varied for each full calendar year shown. If the sales charges were reflected, returns shown would be lower. The table below the bar chart compares the Fund's returns (after applicable sales charges shown in the *Shareholder Fees* table in this prospectus) for the periods shown with those of two broad-based indexes: the S&P 500<sup>®</sup> Index, the Fund's primary benchmark for equity securities, and the Bloomberg U.S. Aggregate Bond Index, the Fund's primary benchmark for debt securities. The table below also compares the Fund's returns with a secondary, custom index, the Blended Benchmark. The percentage of the Fund's assets allocated to underlying stock and bond Portfolio Funds will vary, and accordingly the composition of the Fund's portfolio will not always reflect the composition of the Blended Benchmark.

The performance of one or more share classes shown in the table below begins before the indicated inception date for such share class. The returns shown for each such share class include the returns of the Fund's Class Inst shares for periods prior to its inception date.

Except for differences in annual returns resulting from differences in expenses and sales charges (where applicable), the share classes of the Fund would have substantially similar annual returns because all share classes of the Fund invest in the same portfolio of securities.

The after-tax returns shown in the *Average Annual Total Returns* table below are calculated using the highest historical individual U.S. federal marginal income tax rates in effect during the period indicated in the table and do not reflect the impact of state, local or foreign taxes. Your actual after-tax returns will depend on your personal tax

Columbia Thermostat Fund<sup>SM</sup>

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situation and may differ from those shown in the table. In addition, the after-tax returns shown in the table do not apply to shares held in tax-advantaged accounts such as 401(k) plans or Individual Retirement Accounts (IRAs). The after-tax returns are shown only for Class A shares and will vary for other share classes.

The Fund's performance prior to May 2018 reflects returns achieved following a principal investment strategy with a single form of asset allocation table. While the Fund now follows a principal investment strategy with two potential forms of asset allocation tables, as described above in the *Principal Investment Strategies* section, the form of the Fund's currently effective asset allocation table was in place from the Fund's inception in 2002 through April 30, 2020. The Fund's performance prior to May 1, 2020 and after April 30, 2021 reflects the current form of allocation table. The Fund's performance from May 1, 2020 through April 30, 2021 reflects a different form of asset allocation table.

**The Fund's past performance (before and after taxes) is no guarantee of how the Fund will perform in the future.** Updated performance information can be obtained by calling toll-free 800.345.6611 or visiting columbiathreadneedleus.com.

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| | | | |
|:---|:---|:---|:---|
| **Year by Year Total Return (%)**<br> **as of December 31 Each Year\***<br>| &nbsp;&nbsp; **Best and Worst Quarterly Returns**<br> **During the Period Shown in the Bar Chart** | &nbsp;&nbsp; **Best and Worst Quarterly Returns**<br> **During the Period Shown in the Bar Chart** | &nbsp;&nbsp; **Best and Worst Quarterly Returns**<br> **During the Period Shown in the Bar Chart** |
| ![](g607054bg_655.jpg) | &nbsp;&nbsp; Best | 2nd Quarter 2020 | 13.23% |
| ![](g607054bg_655.jpg) | &nbsp;&nbsp; Worst | 2nd Quarter 2022 | -6.88% |

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**Average Annual Total Returns After Applicable Sales Charges (for periods ended December 31, 2025)\***

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| | | | | |
|:---|:---|:---|:---|:---|
|  | &nbsp;&nbsp;&nbsp; **Share Class** <br> **Inception Date**<br>| **1 Year** | **5 Years** | **10 Years** |
| **Class A** | 03/03/2003 |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; returns before taxes |  | 8.18% | 3.64% | 6.91% |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; returns after taxes on distributions |  | 6.89% | 1.96% | 5.21% |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; returns after taxes on distributions and sale of Fund shares |  | 4.87% | 2.20% | 4.84% |
| **Class C** returns before taxes | 03/03/2003 | 12.86% | 4.10% | 6.74% |
| **Class Inst** returns before taxes | 09/25/2002 | 15.02% | 5.14% | 7.81% |
| **Class Inst2** returns before taxes | 11/08/2012 | 15.12% | 5.20% | 7.86% |
| **Class Inst3** returns before taxes | 11/08/2012 | 15.20% | 5.24% | 7.90% |
| **Class S** returns before taxes | 10/02/2024 | 15.02% | 5.14% | 7.81% |
| &nbsp;&nbsp; **Blended Benchmark** (Secondary Benchmark; an equally weighted custom <br> composite of the Fund's primary benchmarks for equity and debt securities, <br> established by the Investment Manager; reflects no deductions for fees, expenses <br> or taxes)<br>|  | 12.64% | 6.99% | 8.50% |
| &nbsp;&nbsp; **S&P 500**<sup>®</sup> **Index** (Primary Equity Benchmark; reflects no deductions for fees, <br> expenses or taxes)<br>|  | 17.88% | 14.42% | 14.82% |
| &nbsp;&nbsp; **Bloomberg U.S. Aggregate Bond Index** (Primary Debt Benchmark; reflects no <br> deductions for fees, expenses or taxes)<br>|  | 7.30% | -0.36% | 2.01% |

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Class A share performance (without sales charges) is shown in the bar chart and after-tax returns in the table are shown for Class A shares because Class A shares have at least ten calendar years of performance and Class A shares are the most common share class across the Columbia Funds complex that are available for investment by the general public.

Columbia Thermostat Fund<sup>SM</sup>

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**Fund Management**

**Investment Manager:** Columbia Management Investment Advisers, LLC

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| | | | |
|:---|:---|:---|:---|
| **Portfolio Management** | **Title** | **Role with Fund** | **Managed Fund Since** |
| Alex Rivas | Associate Portfolio Manager | Portfolio Manager | 2022 |
| Corey Lorenzen, CFA | Senior Portfolio Manager | Portfolio Manager | 2023 |

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**Purchase and Sale of Fund Shares**

You may purchase or redeem shares of the Fund on any business day by contacting the Fund in the ways described below:

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| | | | |
|:---|:---|:---|:---|
| **Online**  | **Regular Mail** | **Express Mail** | **By Telephone** |
| columbiathreadneedleus.com/investor/ | &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Columbia Management<br> Investment Services Corp. <br> P.O. Box 219104<br> Kansas City, MO 64121-9104<br>| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Columbia Management<br> Investment Services Corp. <br> 801 Pennsylvania Ave., STE. 219104<br> Kansas City, MO 64105-1307<br>| 800.422.3737 |

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You may purchase shares and receive redemption proceeds by electronic funds transfer, by check or by wire. If you maintain your account with a broker-dealer or other financial intermediary, you must contact that financial intermediary to buy, sell or exchange shares of the Fund through your account with the intermediary.

The minimum initial investment amounts for the share classes offered by the Fund are shown below:

**Minimum Initial Investment** 

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| | | | |
|:---|:---|:---|:---|
| **Class** | &nbsp;&nbsp; **Category of eligible** <br> **account**<br>| &nbsp;&nbsp; **For accounts other than**<br> **Systematic Investment**<br> **Plan accounts (as described in the Fund's Prospectus)**<br>| &nbsp;&nbsp; **For Systematic Investment**<br> **Plan accounts**<br>|
| **Classes A & C** | &nbsp;&nbsp; All accounts other than <br> IRAs<br>| $2000 | $100 |
| **Classes A & C** | IRAs | $1000 | $100 |
| **Class Inst** | All eligible accounts | &nbsp;&nbsp; $0, $1,000 or $2,000 <br> depending upon the category<br> of eligible investor<br>| $100 |
| **Class Inst2**  | All eligible accounts |  | N/A |
| **Class Inst3** | All eligible accounts | &nbsp;&nbsp; $0, $1,000, $2,000<br> or $1 million depending<br> upon the category of<br> eligible investor<br>| &nbsp;&nbsp; $100 (for certain<br> eligible investors)<br>|

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More information about these minimums can be found in the *Buying, Selling and Exchanging Shares - Buying Shares* section of the prospectus. There is no minimum additional investment for any share class.

Class S shares are available (i) to be held, but not purchased, by accounts of financial intermediaries that, with specific written permission from the Distributor, have instructed the Fund to exchange Class Inst shares for Class S shares; and (ii) to be held and purchased by omnibus group retirement plans that (A) opened and, subject to exceptions, funded a Class Inst share account as of the close of business on March 28, 2013 and have continuously held Class Inst shares in such account through at least September 30, 2024 and (B) received specific written permission from the Distributor to exchange Class Inst shares for Class S shares. Only omnibus retirement plans referenced in (ii) above may purchase Class S shares, open new Class S accounts, or add new plan participants to a Class S shares omnibus retirement plan account. Otherwise, Class S shares are not available for purchase (other than through the reinvestment of distributions on Class S shares).

**Tax Information**

The Fund normally distributes net investment income and net realized capital gains, if any, to shareholders. These distributions are generally taxable to you as ordinary income or capital gains, unless you are investing through a tax-advantaged account, such as a 401(k) plan or an IRA. The use of a fund-of-funds structure could affect the timing, amount and character of distributions to you and therefore may increase the amount of taxes payable by you. If you are investing through a tax-advantaged account, you may be taxed upon withdrawals from that account.

Columbia Thermostat Fund<sup>SM</sup>

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

If you purchase the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and its related companies — including Columbia Management Investment Advisers, LLC (the Investment Manager), Columbia Management Investment Distributors, Inc. (the Distributor) and Columbia Management Investment Services Corp. (the Transfer Agent) — may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your financial advisor to recommend the Fund over another investment. Ask your financial advisor or visit your financial intermediary's website for more information.

Columbia Thermostat Fund<sup>SM</sup>

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Columbia Threadneedle Investments (Columbia Threadneedle) is the global brand name of the Columbia and Threadneedle group of companies.

The Fund is distributed by Columbia Management Investment Distributors, Inc., 290 Congress Street, Boston, MA 02210.© 2026 Columbia Threadneedle. All rights reserved.

**columbiathreadneedleus.com**SUM235_12_T01_(05/26)

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