The son has a BILL of Sale for $200,000 + $40,000 Interest, it will be paid off over 10 years. I can show all of that income for the father with the 4797. Where can I show the expense for the son? He is paying it monthly, $1,600 principal and $400 Interest. I believe that the 4797 on the father's return negates the need for the son to give him a 1099INT, but how does the son get to show the money he is paying?