Do I need an Australian business number?
You may need to supply your payer with an Australian business number (ABN). If you don't, your payer may be required to withhold at the top rate of tax, currently 49%, from your payments.
In limited circumstances you do not need to supply your payer with an ABN. These include where your income is either:
It is your payer's responsibility to be satisfied that you do not need to provide your ABN.