You should lodge your outstanding tax returns as soon as possible and before the Australian Taxation Office takes any action to have you lodge these tax returns. Once they have begun any action, it could result in a court conviction. The ATO may charge a penalty of $170 for every 28 days that the return is outstanding. The maximum penalty is $850 even if you are due a refund. In addition, the ATO will charge interest. This is called the general interest charge and is levied on any outstanding monies. The rates can be found via this link. Karis Tax office can assist you to lodge your outstanding prior year returns.