Where can I find the amount of my excluded gain for my home installment sale?

You'll need to find the Form 6252 for the year in which you sold your main home. For several years, the excluded gain for a home installment sale has been found on Part I, Line 15 of Form 6252, labeled, "If the property described on Line 1 above was your main home, enter the amount of your excluded gain (see instructions). Otherwise, enter -0-."