Social insurance number (SIN)
Your SIN is the authorized number for income tax purposes under section 237 of the Income Tax Act and is used for 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, inform 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.
Completing your tax return
Enter your SIN on the first line of the "Information about you" area of the "Identification" section on page 1 of your tax return.
Forms and publications
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