The ATO says, “In certain circumstances, we will remove some or all of an individual’s tax debt. We call this ‘release’ from payment of particular tax liabilities.
“We can only assess releasing you from debt in circumstances where you are experiencing serious hardship. We define serious hardship as when payment of your debt would leave you unable to provide food, accommodation, clothing, medical treatment, education or other necessities for yourself, family, or others for whom you are responsible.
“We consider applications for release against the criteria outlined in Practice Statement Law Administration PS LA 2011/17- Debt relief which has been summarised in How is release assessed.”
For more information see the link blow:

https://www.ato.gov.au/Individuals/Payments-to-ATO/Help-with-paying/Release-from-your-tax-debt/