As a taxpayer, you are required to have a tax file number (TFN). Apart from serving as a means of identification of individual taxpayers, the number also helps the ATO in its collection of tax from revenue that may otherwise escape the tax net.

If you are an employee, you are required to provide your employer with your TFN and, subject to some exceptions, you may choose to quote the TFN to investment bodies, such as banks, credit unions, building societies and companies issuing dividends. Unless an exemption applies, if you do not quote your TFN, tax will be deducted from interest and dividend payments at the highest marginal tax rate plus the Medicare levy under the PAYG system. The amount of tax deducted will reduce the amount of tax payable on your taxable income, but will not be refunded until an income tax return for the year is lodged.