As long as you didnt owe money to Revenue Canada, you can claim your taxes for the last 7 years. In Ontario you can claim PST if your 16 and up, and GST if your 19 and up. So even if you didn't have an income for the year, you are still entitled to those refunds. If you paid tuition for your school, you can claim that too (provided you didn't let someone else claim it). The sad part is that you must file each year seperately. Call Revenue Canada and ask them to send the forms for the years you wish to claim.