Number to check
Use a number you are authorised to handle.
Your TFN check
Ready to checkUnavailable. Check the message beside your input.
- Enter a TFN
The check runs on this device after you enter a number.
- Not checked
- Not checked
What a TFN Check Can Establish
A tax file number (TFN) checksum check tests whether the digits satisfy an arithmetic rule. A pass cannot establish that the Australian Taxation Office (ATO) issued the number or that it belongs to a particular person.
This TFN validator accepts eight or nine digits, with spaces allowed. It recognises the eight-digit legacy format and checks the checksum of nine-digit entries. An eight-digit entry receives “Checksum not assessed”, which is not an invalid-number verdict.
For nine-digit entries, the tool multiplies each digit by its position’s weight, then adds the products. A total divisible by 11 passes. For example, a total of 154 passes because 154 divided by 11 is 14; a total of 164 fails.
Clearwater publishes the nine-digit checksum procedure. The ATO’s technical specification describes TFN validation and recognises both lengths. The result returns no tax record, account status or identity information.
Handling an Invalid Result
A failed arithmetic check means the entered digits do not satisfy the nine-digit checksum. It cannot identify which digit was transcribed incorrectly.
- Compare every digit with the original tax document you are authorised to handle.
- Correct only a copying error that the source document confirms, then run the check again.
- If the entered number matches the source, retain the source unchanged and resolve the discrepancy through the authorised tax-record process.
Do not change a digit to force a pass. A TFN calculator cannot generate a replacement identifier or establish that another number belongs to the person.
Do not request a TFN as a routine loan requirement. The Office of the Australian Information Commissioner explains who can collect and use TFN information. A person can remove their TFN from a document before supplying it, including when the recipient can otherwise collect it.
Keeping the Number on the Device
The checker performs its calculation in this browser. It makes no network lookup and keeps no saved history. The masked number is excluded from results and screen-reader announcements.
Select “Clear number” to erase the entry and result. Reloading the page starts with an empty field. Leaving the page also clears the entry before browser-history restoration.
Use the checker only for information you are authorised to handle. A passing checksum does not authorise collection, storage or disclosure of the number.