Your SIN is the authorized number for income tax purposes under section 237 of the Income Tax Act and is used under certain federal programs. You must give it to anyone who prepares information slips (such as a T3, T4, or T5 slip) for you. Each time you do not give it when you are supposed to, you may have to pay a $100 penalty. Check your slips. If your SIN is missing or is incorrect, advise the slip preparer. You must also give it to us when you ask us for personal tax information.
Your SIN card is not a piece of identification, and it should be kept in a safe place. For more information, or to get an application for a SIN, contact Service Canada.
To apply for a SIN, you must complete an application form which you can get from Service Canada.
You must also provide a primary document proving your identity and status in Canada, as well as a supporting document if the name on your primary document is different from the one you are currently using. It is important that documents are originals and that they are written in English or French.
For more information, visit Service Canada. You will find the addresses and telephone numbers of their offices on their Web site.
Enter your SIN on the first line of the "Information about you" area of the "Identification" section on page 1 of your tax return.