Tax file number
Your unique identifier in the Australian tax system, used by the ATO, employers, banks and super funds.
A TFN is free, issued once, and stays with you for life regardless of name changes, job changes, or time spent overseas. You are not legally required to have one, but the practical consequences of going without are severe.
Without a TFN, employers must withhold tax at the top marginal rate plus Medicare levy, banks withhold tax on interest at the highest rate, and you cannot lodge a return normally or receive most government benefits.
Your TFN is sensitive information and a prime target for identity theft. Legitimate requests come from employers, banks, super funds, and Centrelink — never from someone contacting you unexpectedly by phone or message.
The cost of not supplying one
Start a job without providing your TFN and your employer must withhold at the top rate. You get the excess back at tax time, but you have lent the ATO a large slice of your pay in the meantime.
The bit people get wrong
Scam calls claiming your TFN has been 'suspended' or is 'linked to criminal activity' are common. A TFN cannot be suspended, and the ATO never demands immediate payment by phone or threatens arrest.
Common questions
How do I find my TFN?
It appears in myGov under ATO services, on any prior notice of assessment, on a payment summary, or via your tax agent or super fund.
Do I need to give my TFN to my super fund?
You are not obliged to, but without it the fund taxes contributions at a higher rate and cannot accept personal after-tax contributions, so withholding it is costly.
What should I do if my TFN is compromised?
Contact the ATO immediately. They can apply additional security to your record and monitor it for misuse. A TFN is only reissued in genuine cases of identity crime.