The ATO knows that many taxpayers are facing lasting impacts left in the wake of natural disasters, so if they find their records have been lost or destroyed, whether in cyclones, floods or bushfires, the ATO can help.  According to ATO Assistant Commissioner Tim Loch:

Government agencies, private health funds, financial institutions and businesses provide information to the ATO which is available to tax agents and automatically included in returns by the end of July.

If taxpayers have lost receipts due to a natural disaster, the ATO can accept reasonable claims without evidence, so long as it’s not reasonably possible to access the original documents (although the taxpayer may be required to tell the ATO how they calculated the claim).