COLUMBIA THERMOSTAT FUND CLASS A (CTFAX) Exchange: NMFQS

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 Wanger Asset Management, LLC, the Fund’s investment adviser (the Investment Manager) or its affiliates, including Columbia Management Investment Advisers, LLC (Columbia Management), serves as investment adviser or principal underwriter (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® Index.Generally, the Fund’s allocation to stock funds increases as the S&P 500® Index declines and decreases as the S&P 500® Index rises. When the S&P 500® 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® 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 set forth below. 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 below under Determination of Current Market State. Such determination will be made on at least an annual basis and will be reflected in the asset allocation table disclosed in this 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.From the Fund's inception in 2002 through April 2020, the asset allocation table in place reflected the Investment Manager’s determination that the equity market was “expensive.” The Fund’s current asset allocation table, which is set forth below, reflects the Investment Manager’s determination that the equity market is currently “normal.” The structure of the Fund's current allocation table reflects the form that has been in place since May 1, 2020. Stock/Bond Allocation Table   How the Fund will Invest the Stock/Bond Assets Level of the S&P 500® Index Stock Percentage Bond Percentage over 2677 50% 50% between 2570 – 2677 55% 45% between 2467 – 2570 60% 40% between 2368 – 2467 65% 35% between 2273 – 2368 70% 30% between 2182 – 2273 75% 25% between 2095 – 2182 80% 20% between 2011 – 2095 85% 15% under 2011 90% 10% When the S&P 500® Index moves into a new band on the table, the Fund will rebalance the stock/bond mix to reflect the new S&P 500® Index price level by redeeming shares of some Portfolio Funds and purchasing shares of other Portfolio Funds. Any such rebalancing typically will be implemented promptly. However, there are two circumstances when a rebalancing may be implemented over a longer timeline. First, when a rebalancing or allocation table change would trigger a 10% point or greater change in stock and bond allocations or individual Portfolio Funds, the rebalancing may be implemented over a period of up to two weeks, if deemed by the Investment Manager to be in the best interest of shareholders. The second exception is a “31-day Rule;” in order to reduce taxable events and minimize short-term trading if the S&P 500® Index price moves back and forth across a band in the allocation table, after the Fund has increased its percentage allocation to either stock funds or bond funds, it will not decrease that allocation for at least 31 days. Following a change in the Fund’s stock/bond mix, if the S&P 500® Index remains within the same band for a while, normal market fluctuations will change the values of the Fund’s holdings of stock Portfolio Funds and bond Portfolio Funds. The Investment Manager will invest cash flows from sales (or redemptions) of Fund shares to bring the stock/bond mix back toward the allocation percentages for that S&P 500® Index band. For example, if the S&P 500® Index is in the 2095 band, and the value of the holdings of the stock Portfolio Funds has dropped to 78% of the value of the holdings of all Portfolio Funds, the Investment Manager would invest new cash in the stock Portfolio Funds (or cash for redemptions would come from the bond Portfolio Funds) to restore the 80% stock allocation. If the 31-day Rule is in effect, the Investment Manager will invest new cash at the stock/bond percentage allocation as of the latest rebalancing.As another illustrative example, suppose the following: Date Level of the S&P 500® Index How the Fund will invest the Stock/Bond Assets(1) Nov. 1 We begin when the market is 2200 75% stocks, 25% bonds Dec. 1 The S&P 500® goes to 2275 rebalance 70% stocks, 30% bonds Dec. 6 The S&P 500® drops back to 2250 no reversal for 31 days Jan. 2 The S&P 500® is at 2230 rebalance 75% stocks, 25% bonds Jan. 20 The S&P 500 drops to 2180 rebalance 80% stocks, 20% bonds(2) Jan. 30 The S&P 500® goes to 2225 no reversal for 31 days Feb. 20 The S&P 500® is at 2200 rebalance 75% stocks, 25% bonds (1) For each rebalancing the Fund will trade the underlying stock and bond Portfolio Funds on the next business day.(2) The market has made a continuation move by going through a second action level, not a reversal move, so the 31-day Rule does not apply in this case.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.The following table shows 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. As described more fully below, the Investment Manager may substitute or add additional Portfolio Funds at any time, including funds introduced after the date of this prospectus. The target percentage within each asset class category is achieved by rebalancing the investments within the asset class whenever the S&P 500® Index moves into a new band on the allocation table, subject to the 31-day Rule described above. The Fund will not liquidate its investment in one Portfolio Fund in order to invest in another Portfolio Fund except in connection with a rebalancing due to a move of the S&P 500® Index into a new band (or due to a change by the Investment Manager in the Portfolio Funds or to the relative target percentages among them). Until a subsequent rebalancing, the Fund’s cash flows are invested in, or redeemed from, the Portfolio Funds in a manner that will reduce any deviation of the relative values of the Fund’s holdings of the Portfolio Funds from the percentages shown below. Allocation of Stock/Bond Assets Within Asset Classes Stock Funds Type of Fund Allocation Columbia Acorn® Fund Small/Mid-cap growth 10% Columbia Acorn International® Small/Mid-cap international growth 10% Columbia Contrarian Core Fund Large-cap blend 10% Columbia Dividend Income Fund Large-cap value 10% Columbia Large Cap Enhanced Core Fund Large-cap blend 10% Columbia Large Cap Index Fund Large-cap blend 30% Columbia Research Enhanced Core ETF Beta Advantage® U.S. equity 10% Columbia Select Mid Cap Value Fund Mid-cap value 10% Total   100% Bond Funds Type of Fund Allocation Columbia Corporate Income Fund Corporate bond 10% Columbia Diversified Fixed Income Allocation ETF Beta Advantage® multi-sector bond 10% Columbia Quality Income Fund Government bond 20% Columbia Short Term Bond Fund Short term bond 15% Columbia Total Return Bond Fund Intermediate core bond 10% Columbia U.S. Treasury Index Fund U.S. Treasury notes/bonds 35% Total   100% See the Portfolio Funds Summary section of this 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 load on its purchases of shares of the Portfolio Funds.The Investment Manager has the authority to review the Portfolio Funds and to change the relative percentages among them or to add or eliminate funds. Such review will occur on at least an annual basis and will be reflected in the Portfolio Funds table disclosed in this prospectus.Determination of Current Market StateJust as a thermostat may be set at different ranges for different seasons, the Fund’s allocation of assets between stock and bond funds is expected to be set at different range bands depending principally on the Investment Manager’s view of how expensive the equity market is compared to historical levels.At least annually, the Investment Manager will conduct a review of the current equity market price levels compared to historical price levels, and will determine if the equity market is in an “expensive” state, or a “normal” state. This review will begin with a comparison of the S&P 500® Index’s cyclically adjusted price-to-earnings ratio for the prior seven years against a 40-year history, but the Investment Manager will also take into account additional quantitative or qualitative market factors, including for example, trends in equity price measures and comparisons of equity prices against prices for other asset classes. Based on its determination of the current market state, the Investment Manager will select the form of allocation table to be effective in the Fund’s current prospectus. Also as part of this review, the Investment Manager will update the median historical information used in the table, and the resulting S&P 500® Index levels used to create the bands around the median, regardless of the market state.As noted below, the form of table used for a “normal” market is expected to be different from that used for an “expensive” market.Generally, the Investment Manager will determine the current state of the equity market to be “normal” when its analysis of the S&P 500® Index’s cyclically adjusted price-to-earnings ratio for the prior seven years is outside the top quartile of ratio observations over a 40-year history. The “normal” equity market form of allocation table for the Fund is structured around an implied S&P 500® Index trading range median of 50% stocks/50% bonds (the 50/50 Band), with allocations to bonds decreasing through stratified range bands below the 50/50 Band, and allocations to stocks and bonds set at 50% stocks/50% bonds for all trading levels above the 50/50 Band, as shown by the following example: “Normal” Equity Market Form of Stock/Bond Allocation Table Level of the S&P 500® Index Stock Percentage Bond Percentage above trading range that is 2% below implied median (50/50 Band)* 50% 50% 4% trading range below bottom of range above 55% 45% 4% trading range below bottom of range above 60% 40% 4% trading range below bottom of range above 65% 35% 4% trading range below bottom of range above 70% 30% 4% trading range below bottom of range above 75% 25% 4% trading range below bottom of range above 80% 20% 4% trading range below bottom of range above 85% 15% below bottom of trading range above 90% 10% *Implied median price level as calculated by the Investment Manager.The “normal” form of allocation table has been in place since May 1, 2020.Generally, the Investment Manager will determine the current state of the equity market to be “expensive” when its analysis of the S&P 500® Index’s cyclically adjusted price-to-earnings ratio for the prior seven years is within the top quartile of ratio observations over a 40-year history. The “expensive” equity market form of allocation table for the Fund is also structured around the 50/50 Band, with allocations to bonds decreasing through stratified range bands below the 50/50 Band and allocations to bonds increasing through stratified range bands above the 50/50 Band, as shown by the example below. The “expensive” form of allocation table was in place from the Fund’s inception through April 2020. “Expensive” Equity Market Form of Stock/Bond Allocation Table Level of the S&P 500® Index Stock Percentage Bond Percentage above top of trading range below 10% 90% 4% trading range above top of range below 15% 85% 4% trading range above top of range below 20% 80% 4% trading range above top of range below 25% 75% 4% trading range above top of range below 30% 70% 4% trading range above top of range below 35% 65% 4% trading range above top of range below 40% 60% 4% trading range above top of range below 45% 55% 4% trading range centered on implied median (50/50 Band)* 50% 50% 4% trading range below bottom of range above 55% 45% 4% trading range below bottom of range above 60% 40% 4% trading range below bottom of range above 65% 35% 4% trading range below bottom of range above 70% 30% 4% trading range below bottom of range above 75% 25% 4% trading range below bottom of range above 80% 20% 4% trading range below bottom of range above 85% 15% below bottom of trading range above 90% 10% *Implied median price level as calculated by the Investment Manager.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.