If your mortgage is not fully open, you may be charged a penalty if you want to pay off all or part of your mortgage before the end of the fixed term. The normal prepayment penalty is the greater of three months\' interest or the Interest Rate Differential (IRD) on the amount to be prepaid. CMHC (for insured mortgages) and a few of the major lenders set the maximum penalty at 3 months interest after the mortgage has been in effect for three years, regardless of the number of times it has been renewed.