Canada SIN Check Digit Validator (Social Insurance Number)

Free tool to validate and calculate the check digit of a Canadian Social Insurance Number (SIN). Enter 8 or 9 digits and it auto-detects the format, verifies the checksum with the Luhn algorithm (mod 10), and identifies the registrant category (permanent resident, temporary resident, etc.) from the leading digit. Everything runs in your browser.

What is the Canada SIN check digit validator?

This free online tool validates and calculates the check digit of a 9-digit Canadian Social Insurance Number (SIN), and also identifies the registrant category (permanent resident, temporary resident, or unassigned) from its leading digit. It follows the Luhn algorithm (mod 10), the same checksum scheme used to validate credit card numbers.

It automatically detects the input format based on length (8 or 9 digits), so there's no mode to switch manually. If you enter a number that already includes a check digit, it validates it; if you enter the 8-digit body only, it calculates and appends the correct check digit. Note that this tool only confirms whether the format is valid — it cannot identify whether the number was actually issued to a real person (you'll need to check the person's ID documents to confirm that).

How to use it

Enter the SIN You can paste it with spaces or hyphens still in place.
Check the detected format and result The detected format (with or without a check digit) and the validation or calculation result are shown.
Check the registrant category The category (permanent resident, temporary resident, or unassigned) identified from the leading digit is displayed.
Try another number Use the clear button to reset the input and check a different number.

Tips for getting more out of it

You can paste a number that still has spaces or hyphens — they are stripped automatically before the calculation runs.
Enter the 8-digit body without a check digit and the tool automatically fills in the correct check digit to show the full 9-digit number.
A SIN starting with 9 is issued to a temporary resident (someone holding a work or study permit). It expires as soon as that permit's validity period ends.
This tool only checks whether the format (check digit) is valid — it cannot confirm whether the number was actually issued to a real person. Confirming that requires the person's ID documents or an inquiry to the CRA.
A SIN is highly sensitive personal information. Even when checking a number given to you by someone else, clear the input promptly afterward and avoid showing the screen to anyone else.

Use cases

Catching HR/payroll data entry errors

Before registering a new hire's SIN in a payroll system, catch transcription errors with the check digit.

Managing temporary worker employment

Since a SIN starting with 9 expires along with the work permit, check the registrant category as a reference when assessing whether employment can continue.

Reference for building payroll validation logic

Use it as a reference to confirm the expected behavior of a SIN validation (Luhn algorithm) implemented in a Canada-facing HR or payroll system.

Digitizing old paperwork

When entering SINs from paper documents into a database, use the check digit to catch OCR misreads.

Glossary

SIN (Social Insurance Number): A 9-digit number used in Canada for employment insurance, pensions, and tax administration, introduced in 1964 and now also used as a form of identification.
Luhn algorithm: A checksum formula (mod 10) devised by IBM's Hans Peter Luhn in 1954, also widely used to validate credit card numbers.
Check digit: The final digit of a SIN, calculated from a formula to detect typos and transcription errors.
Temporary resident: Someone staying in Canada under a work or study permit rather than permanent residency or citizenship. Their SIN starts with 9.
Service Canada: The Canadian government agency responsible for issuing and administering SINs.
CRA (Canada Revenue Agency): The government agency that administers taxation and benefits in Canada. A SIN is also used for tax filing.

Frequently Asked Questions

It's the 9th digit of a SIN, derived from the other 8 digits using the Luhn algorithm (mod 10). It's designed to catch transcription and typing errors — it does not guarantee that the number itself was actually issued.

It likely means a transcription or OCR error. First double-check the original document (a SIN card or notice letter). If it still fails, ask the person to show their SIN card, or contact the CRA or Service Canada if needed.

It indicates the number was issued to a temporary resident (someone without Canadian permanent residency or citizenship) holding a work or study permit. This category of SIN is tied to the permit's expiry date and becomes invalid once it expires.

No. This tool only checks whether the check digit calculation is valid — it cannot verify whether the number was actually issued by Service Canada. If you need to confirm that, ask for the person's ID documents.

No. All calculations run entirely in your browser using JavaScript; nothing is sent to an external server. That said, since a SIN is highly sensitive personal information, we recommend clearing the input promptly after checking it.

Side Note — Protected by the same scheme as your credit card

Canada's Social Insurance Number (SIN) was introduced in 1964 as a 9-digit number used for employment insurance, pensions, and tax administration. It was originally meant to track pension plan membership, but it has since become an essential piece of identification for living and working in Canada — required for payroll paperwork, opening bank accounts, and filing tax returns.

The Luhn algorithm used for the trailing check digit is actually the same verification scheme widely used for credit card numbers and some corporate identification codes. Devised in 1954 by IBM scientist Hans Peter Luhn, it catches most single-digit typos and adjacent digit-swap errors using nothing more than doubling digits at alternating positions and summing their digit values.

The leading digit of a SIN carries meaning too. A number starting with 9 is issued to a temporary resident (someone without Canadian permanent residency) who holds a work or study permit, and it expires the moment that permit's validity period ends. Employers who aren't aware of this rule have run into real trouble continuing payroll with an expired SIN for a temporary worker, making it a detail HR and payroll staff shouldn't overlook.

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