TFN Generator

What this tool does

It generates random nine-digit numbers that satisfy the Australian Taxation Office's checksum rule for Tax File Numbers. They pass TFN validators, which makes them useful for filling test databases, exercising form validation and writing test fixtures.

They are not real TFNs. They are not issued to anyone, they identify nobody, and using them on an official form is fraud. This tool exists so you don't have to put your own TFN into a staging environment.

How the TFN checksum works

A TFN is valid when each digit is multiplied by its position weight and the total divides evenly by 11.

The weights are:

1, 4, 3, 7, 5, 8, 6, 9, 10

So for the TFN 123456782:

(1×1) + (2×4) + (3×3) + (4×7) + (5×5) + (6×8) + (7×6) + (8×9) + (2×10) = 253
253 ÷ 11 = 23 exactly  → valid

This tool doesn't guess and re-check. It draws the first eight digits at random, then solves directly for the check digit that satisfies the rule. Because the ninth weight is 10, and 10 ≡ −1 (mod 11), the constraint reduces neatly to check digit ≡ sum of the first eight (mod 11). When that lands on 10 there is no single digit that works, so the number is redrawn.

How to use it

Pick how many TFNs you want (up to 50) and whether to format them as plain digits or in the conventional XXX XXX XXX grouping. Click Generate, then copy or download.

Will these pass a real validator?

They'll pass a checksum validator, which is what most software implements. They will not match anything in the ATO's records, and any system that checks against the real register will reject them — as it should.

Privacy

Numbers are generated in your browser. Nothing is sent to a server, and nothing is stored.