Dear Liz: I am selling my house and will not be buying another one. I believe that I know the rules of capital gains taxes in general. However, must I include the capital gains of previous homes, even those experienced many years ago?

Answer: Possibly.

Before 1997, homeowners could avoid capital gains taxes by rolling their profits into another home, as long as the purchase price of the new house was equal to or greater than the home they sold. Homeowners 55 and older could get a one-time exclusion of up to $125,000.

The rules changed in 1997. Now homeowners can exclude up to $250,000 of home sale gains as long as they have owned and lived in the home at least two of the prior five years. A married couple can exclude up to $500,000.

If you have not sold a home since the rules changed, however, any previously deferred gains would lower the tax basis on your current home.

Let’s say you bought your current home for $300,000 prior to 1997. Normally, that amount (plus certain other expenses, including qualifying home improvements) would be your tax basis. If the net proceeds from your sale were $500,000, for example, you would subtract the $300,000 basis from that amount for a capital gain of $200,000.

But now let’s say you rolled $200,000 of capital gains from previous home sales into your current home. That amount would be subtracted from your tax basis, so your capital gain would be $400,000 — the $500,000 net sale proceeds minus your $100,000 tax basis.

Before selling any home, you should consult with a tax pro to make sure you understand how capital gains taxes may affect the sale. You don’t want to find out you owe a big tax bill after you’ve spent or invested the proceeds.