Home Tax File Number Australia
Australia Tax File Number validator
How the Tax File Number format works
- Format
- 9 digits
- Example
- 123456782
Things to watch for
- Weighted mod-11 checksum over all 9 digits
- Format + checksum only — does not confirm the TFN is actually issued or active
- Older 8-digit TFNs exist but are no longer issued — this validator targets the current 9-digit format
^[0-9]{9}$A Tax File Number (TFN) is the 9-digit identifier the Australian Taxation Office (ATO) issues to individuals and entities for tax and superannuation purposes, usually written in three groups of three (for example, 123 456 782). It shows up on tax returns, super fund paperwork, employment forms, and bank account applications — and because it’s tied so closely to someone’s financial identity, Australian law tightly restricts who can collect, store, and use it.
How this validator works
This tool checks that the input is exactly 9 digits, then runs the ATO’s weighted modulus-11 checksum: each digit is multiplied by a fixed weighting factor, the products are summed, and a genuine TFN’s sum divides evenly by 11. That’s what separates a real TFN from nine random digits — a single mistyped or transposed digit almost always breaks the checksum, which is exactly the kind of error this check is built to catch before a form gets submitted or rejected downstream.
What a pass doesn’t tell you
A checksum pass confirms the number is structurally valid — nothing more. It does not mean the TFN was actually issued, is currently active, or belongs to the person who typed it in. This tool performs no lookup against the ATO or any other register, because no such public lookup exists or should exist; TFNs are sensitive personal identifiers protected under Australian privacy law. Everything here happens client-side: the number you type never leaves your browser and is never stored, logged, or transmitted.
Scope: this page covers TFN format and checksum validation only — not identity verification, ATO record lookup, or confirming a TFN is currently in use. Use it to catch a typo before submitting a form; use the ATO’s own channels for anything involving identity or account status.
Content last reviewed 2026-07-09.
Tax File Number FAQ
How is a TFN checked?
This tool confirms the TFN is 9 digits and runs the ATO's weighted modulus-11 checksum — each digit is multiplied by a fixed weight (1, 4, 3, 7, 5, 8, 6, 9, 10) and the total must divide evenly by 11. It catches a mistyped or transposed digit before you submit a form, all inside your browser.
Does a valid TFN identify a person?
No. A checksum pass only means the number is structurally well-formed — it does not confirm the TFN was ever issued by the ATO, is active, or belongs to anyone in particular. This tool does no lookup against any register and can't link a number to an identity.
Is my TFN sent anywhere when I use this tool?
No. The check runs entirely in your browser using JavaScript — your TFN is never transmitted to a server, logged, or stored anywhere, including by this site. Given how sensitive TFNs are, that's a deliberate design choice, not an afterthought.