No. You need to report T-Slips on the return for the tax year that they were issued. If you have already filed your 2017 tax return, you can make changes to it, but you need to do it through the CRA. However, you
may want to wait until you have gotten your Notice Of Assessment, as the CRA
may correct the error themselves. https://turbotax.community.intuit.ca/replies/2647992
