Social insurance number (SIN)
Your social insurance number (SIN) is the tax identification number used in Canada to identify you for income tax purposes under Section 237 of the Income Tax Act.
For individuals resident in Canada, this unique 9-digit number, issued by Service Canada, is used for income tax filing and certain federal programs.
Your SIN is confidential; however, it must be given to anyone who prepares your information slips (like a T3, T4 or T5 slip), such as your employer, trustee, bank or investment company. You must also give your SIN to the Canada Revenue Agency when you ask them for personal tax information.
Each time that you do not give your SIN when required, you may have to pay a $100 penalty.
Check your slips every year. If your SIN is missing or incorrect, inform your slip preparer.
For more information or to apply for a SIN, see Social Insurance Number (Service Canada).
Completing your tax return
Enter your SIN in "Step 1 – Identification and other information" of your income tax and benefit return.
Forms and publications
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