- This tells you whether the number is correctly formed. It cannot tell you whether it was ever issued, or to whom.
🔒 Your number never leaves this page. The check runs in your browser: nothing is sent, stored or logged, and there is no account.
How the checksum works
The last digit of a SIN is a check digit. The CRA’s published method takes four steps; here they are on its own example, 999 999 998.
Double every second digit
Take the 2nd, 4th, 6th and 8th digits and multiply each by 2.
Add the digits of each product
A product of 18 becomes 1 + 8 = 9. Add the four results.
Add the other digits
Add the 1st, 3rd, 5th and 7th digits. The check digit is left out.
Round up to the next ten
Add the two sums, then find the gap up to the next multiple of 10. That gap must equal the last digit.
| Position | Digit | Doubled | Counted as |
|---|---|---|---|
| 1 | 9 | — | 9 |
| 2 | 9 | 9 × 2 = 18 | 1 + 8 = 9 |
| 3 | 9 | — | 9 |
| 4 | 9 | 9 × 2 = 18 | 1 + 8 = 9 |
| 5 | 9 | — | 9 |
| 6 | 9 | 9 × 2 = 18 | 1 + 8 = 9 |
| 7 | 9 | — | 9 |
| 8 | 9 | 9 × 2 = 18 | 1 + 8 = 9 |
| 9 | 8 | — | = check digit |
| Sum of the doubled digits | 36 |
| Sum of the other digits | 36 |
| Total | 72 |
| Next multiple of 10 | 80 |
| Gap = check digit | 8 |
What a pass does and doesn’t mean
A pass tells you
The nine digits are consistent with each other. A mistyped digit, or two swapped neighbours, will usually be caught. About one in ten random nine-digit strings passes.
A pass does not tell you
That the number was issued, that it is current, or that it belongs to the person giving it. Only Service Canada can confirm a SIN, and it does not offer a public lookup.
Handling a SIN
Share it only when there is a legal reason, such as an employer or a tax slip. This page keeps nothing: close the tab and the number is gone.
SINs that start with 9
ESDC issues SINs beginning with 9 to temporary residents, such as people on work or study permits. This page flags them, because a 9-series number does not prove ongoing status.
Tied to immigration documents
A SIN starting with 9 has an expiry date linked to the person’s permit or other document, and it must be renewed when that document is.
Employers keep it current
ESDC’s guidance for employers covers checking and tracking the expiry date of a 9-series SIN. See the ESDC pages in the sources below.
Frequently asked questions
Can this tell me if a SIN is real?
No. It only checks that the nine digits are consistent with the checksum. A well-formed number may never have been issued, and there is no public database to check against.
Is the number I type sent anywhere?
No. The check is a few lines of JavaScript on this page. Nothing is uploaded, stored or logged, and there are no cookies tied to what you type.
Does the first digit tell me the province?
We do not claim that. The first digit is not given a published province meaning in the sources we use, apart from 9 for temporary residents, so this page does not guess.
Why does a SIN starting with 9 get a warning?
Those are issued to temporary residents and expire with their immigration documents. It is information, not an error: the number can still be valid.
Does the Business Number use the same checksum?
The first nine digits of a Business Number use the same check, according to the CRA sheet. The Business Number validator on this site also checks the program account.
Last updated
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Sources
How we check it
The tests reproduce the CRA’s worked example, 999 999 998, step by step: doubled digits 18, 18, 18, 18; sums 36 and 36; total 72; next ten 80; check digit 8. Changing any digit of that number must make it fail.
The checksum is compared with a second, independently written Luhn routine on 20,000 pseudo-random nine-digit strings, and with the standard Luhn test number 79927398713.
Limits: the CRA sheet is a 2002 archived copy, and ESDC does not publish a lookup. We therefore test the checksum, not whether a SIN was issued. The rule for numbers starting with 9 comes from ESDC’s pages and is not tested against data.