A mortgage loan (fixed-rate mortgage) that pays flat interest only (IO) over an interest only period within its life (10, 15, 20, or 30 years). It is a fully amortizing fixed-rate loan that allows the borrower to pay interest only for the initial interest-only period (a period shorter than the loan’s life). Thereafter, the outstanding balance will be re-amortized over the remaining term. In effect, after the initial IO period, the borrower will have to pay more: principal repayment and interest. At the end of the loan’s life, the mortagage will fully amortize.