When you have an Installment sale of a property where you get payments each year after the year of sale which contain principal and interest in them, then each year you will need to use the original gross profit % calculated to determine the amount of interest income to claim each year and the amount of capital gain to claim each year.
The information that goes into the F6252 form to calculate the gross profit percentage only needs to be entered the year of the sale. The gross profit % is the only information needed on future year returns to be used to calculate the gains for each of the future years based on the amount of principal received each of those future years.
