Have a quick look at your Detailed Tax Summary paying extra attention to line 421 (CPP contributions due) near the bottom. If you're self-employed, you're responsible for paying your own CPP. Since tuition credits are non-refundable credits, they cannot offset CPP owing. The good news is, you'll still have lots of tuition credits left for future years.
*Tip - If you are self-employed, be sure to record all of your business-related expenses no matter how small. These expenses will lower both your tax owing and your CPP due.
