Gather the documents you need. For changing your name on a SIN card, you need your proof of identity, such as an original Canadian birth certificate or Canadian citizenship certificate, and the original legal proof of your name change, such as a court order or marriage certificate.
Get a Social Insurance Number Application. Visit the official website of Service Canada, the Canadian government's online service website, to download an application.
Complete the SIN application. Select the box for "Legal Change of Name" as the application type on the top of the document. You need your old name, new name, address, SIN number, birthplace and date and the names of both your parents. Sign and date the application. Put your original documents with the application.
Mail the application and the documents to Social Insurance Registration, PO Box 7000, Bathurst NB, E2A 4T1. You'll receive the card with the new name and your original documents back in approximately three weeks.