You cannot claim a deduction for the interest on the Parent Plus loan because you are not legally obligated to pay it. Your father can claim a deduction for the interest, even though you paid it. It's treated as if you gave him the money and he used it to make the loan payments. Your father can claim the deduction because he is legally obligated to pay the interest, and you were his dependent when he took out the loan. It doesn't matter whether you are his dependent now.
