If you don't pay the taxes you owe CRA by April 30 every year, it will charge you interest at the agreed interest rate. Usually, the interest is compounded daily on amount of money you owe starting May 1. The interest rate can change every three months. If you can convince the CRA that you have truly tried to get funds to settle the debt but still can't pay the balance in full, you can request a payment arrangement. This is the kind of plan that will help you pay you pay the the taxes.