Australia · identifier format check
Australian TFN validator.
Type a 9-digit tax file number to see whether it passes the weighted check calculation. The test runs on this page only: the number is not sent, saved or logged.
Check a number
Result
Enter a 9-digit TFN and press Check number.
How the TFN check calculation works
A current tax file number has 9 digits. Multiply the digits, left to right, by the weights 1, 4, 3, 7, 5, 8, 6, 9 and 10, add the products, and divide the total by 11. A number that passes leaves no remainder.
Worked example, 123 456 782: 1×1 + 2×4 + 3×3 + 4×7 + 5×5 + 6×8 + 7×6 + 8×9 + 2×10 = 253, which is 11 × 23, so the check passes.
Source: the Australian Taxation Office describes the TFN as a 9-digit number and publishes this weighted-sum validation for software that collects TFNs. Older 8-digit TFNs exist and are not checked here. Calculation checked October 4, 2026.
Frequently asked questions
Does a passing TFN mean it is real?
No. About one in eleven random 9-digit numbers passes the check. A pass only shows the digits are internally consistent; it cannot show the number was issued or who holds it.
Is my number stored or sent anywhere?
No. The calculation runs in your browser and this page loads no advertising or analytics scripts.
Where do I find my own TFN?
Your TFN appears on notices from the ATO and your myGov-linked ATO account. If you cannot find it, contact the ATO directly.
A format check, not verification
This tool cannot confirm that a TFN was issued or belongs to a person. To verify a TFN for payroll, use the ATO’s own channels.