How can I find my tax file number?
Ask your accountant
Your accountant has your tax file number, and the tax file numbers of your associated entities, on file at their office. It is usually stored in a computer system and is easily accessible. Alternatively, your accountant can get your tax file number from your file at the Australian Taxation Office.
Your tax file number appears on your tax return and various other statements, and notices, issued by the Tax Office.
The Tax Office can supply you with your tax file number after you pass a proof of identity test.