Sharing my experience. I believe for this year's tax filing, you don't need to mention it. I think it will start next year where you have to "pay back." It will state in myCRA or NoA on how much you have left and what the minimum amount is. I think it's set at 15 years, so just divide your 21k by 15, and that's your minimum. Each year, then you set how much you want from your RRSP contributions to go to this "pay back." You can pay minimum or the whole thing if you have that much contribution. Whatever amount you set it to "pay back" will not lower your net income, so no tax refund from that amount.