If you sold them this property as an installment sale and you did not use the form 6252 but reported the entire sale in the year of sale on the Sch D and have only been reporting the interest on the return since the sale then you will ONLY report the interest paid this year ... the pay off of the principal is not reported at all ... it was taken into consideration on the return in the year of sale.
However, if you have been reporting this yearly on the form 6252 then you will report the interest and principal paid as usual.
