These are mortgage that allow the borrower not to make repayments by the due date under agreed conditions.
Typically missed payments or underpayments are rolled up and added to the mortgage and must be repaid over the remaining life of the mortgage, unless the lender agrees with you to extend the mortgage term. Normally lenders will not let the total debt exceed their lending limits. If you have made any over payments in the past it is not uncommon that your lender will let you underpay up to the amount of any previous overpayments.
