Yes, the Internal Revenue Service considers a mutual fund exchange the sale of one fund and the purchase of another. You will be responsible for capital gains tax on mutual fund gains if you exchange your fund at a profit, just like you would in an outright sale. Your holding period will determine how much you owe.

I made this "mistake" in 2020.  Is there any remedy for me?  I am on fixed income and the taxes on this exchange are going to kill me.

Have you entered the exchange yet on your tax return?  If you exchange your fund one year or less after you bought it, you'll pay taxes at the short-term capital gains rate, which is the same as you pay on your ordinary income.  If you held the fund for longer than one year, you can take advantage of the long-term capital gains rate.   

Exchanging a losing mutual fund could end up saving you money in taxes. Just like you're responsible for the capital gains if you exchange your fund at a profit, you're also entitled to the benefit of your capital losses if your fund has gone down in value. The IRS allows you to use capital losses to offset any of your other investment gains and up to $3,000 in ordinary income. Additional losses can be rolled forward to future tax years. Because an exchange is considered a sale for tax purposes, you could exchange your losing fund into another to capture the loss. Rather than paying tax on the exchange, you'd actually be lowering your tax bill.

The tax you owe will depend on your basis in the funds, the income you received, and how long you owned the fund that was exchanged.   That link has information specific to mutual funds.   @Glondlo

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