If you failed to designate a repayment in prior years, the required repayment is added into your income as though you had withdrawn the funds in the year.
Each year it is as though you had made the repayment so it is not like you need to catch up. The balance will continue to decrease regardless if you made a payment or not.
There is no tax or financial benefit at this time to enter more then the designated required repayment.
In order to designate a repayment, you will need to have made RRSP contributions to cover the repayments.
