Canada SIN Format Validator

Canadian SIN (Social Insurance Number): 9 digits with a Luhn check

The Social Insurance Number (SIN) is Canada's identifier for work and access to government programs and benefits, administered by Service Canada. The format is 9 digits, conventionally grouped as NNN-NNN-NNN, e.g. 123-456-789. Unlike the US SSN, the SIN does carry a check digit — the 9th digit validates the whole number via the Luhn (mod 10) algorithm.

The Luhn check works on the first 8 digits: double every second digit (positions 2,4,6,8), subtract 9 from any result over 9, add the untouched digits, and the 9th digit is what makes the total a multiple of 10. This is the same checksum used by credit cards, so a single typo or transposition is usually caught immediately.

What the first digit means

• The first digit historically indicated the province/region of registration (e.g. 1 Atlantic provinces, 2–3 Quebec, 4–5 Ontario, 6 Prairies/Territories, 7 Pacific, 8 reserved).
• A SIN starting with 9 is a temporary number issued to people who are not Canadian citizens or permanent residents (e.g. temporary workers/students). These carry an expiry date tied to immigration status.
• A SIN starting with 0 is never issued.

Common pitfalls

• Forgetting the Luhn check: a 9-digit string with a valid first digit can still fail the checksum — always run Luhn.
• Temporary SIN expiry: a 9-series SIN expires with the work permit; a valid format doesn't mean it's currently usable.
• Treating it as ID: Service Canada warns the SIN is not a piece of ID and should be shared only when legally required (employment, tax, benefits) to limit fraud.

FAQ

Does the SIN have a check digit? Yes — the 9th digit is a Luhn (mod 10) checksum over the first eight.

What does a SIN starting with 9 mean? It's a temporary SIN for non-residents, tied to immigration status and an expiry date.

Is a valid SIN proof it's registered? No. The Luhn check confirms it's well-formed; only Service Canada confirms it's assigned and active.