Why don’t you just figure out the interest paid from an amortization schedule. You probably know when you originally got the loan what the interest rate was and the total balance. Just plug those numbers in a amortization calculator like the one found here (http://www.bankrate.com/calculators/mortgages/mortgage-calculator.aspx) and click on the amortization schedule and figure out the interest paid for the year in question. It’s pretty simple to do the math and it will be close enough.