You must lodge a tax return if you are an Australian resident and any of the following apply to you:
(a) You paid tax under the pay as you go (PAYG) system;
(b) You had tax withheld from payments made to you by an employer; or
(c) Your taxable income was more than $18,200.
You must also lodge a tax return if you are a non-resident and you earn Australian-sourced income.
If you are unsure whether you need to lodge a tax return, you can check this based on your personal circumstances on the ATO website here.