Free online tool
TFN Validator.
Check Tax File Number format using ATO weighting rules for 8 and 9 digit TFNs.
Private Local Check
TFNs are private — this tool does not store or transmit your TFN.
Never share your TFN with unverified parties.
Three simple steps
How to use TFN Validator
1
Enter TFN
Paste your 8 or 9 digit TFN.
2
Validate
Run format check based on ATO weighting.
3
Review result
See valid or invalid TFN format.
Helpful answers
Frequently asked questions
Can this tool look up who a TFN belongs to?
No, and no tool legally can. It only checks that the digits satisfy the ATO's checksum. TFNs are protected by the Privacy Act and there is no public lookup.
Is it legal to store customer TFNs?
Only if you are authorised to collect them (for example as an employer or registered agent) and you meet the TFN Rule under the Privacy Act — secure storage, restricted access and secure destruction when no longer needed.