FAQ 71 What records do I need to keep for my Properties?

The ATO have quite a lot of explanatary documents about this topic.

Be aware that a PPR , when sold, will not NORMALLY incur any liablity to pay CGT . However if anything is done to affect the CGT free status ( rent out part of the property or rent out and leave the property for more than 6 years) then a liability to pay CGT on any gain that is made may result.. It is important to keep records EVEN FOR A PPR. Any capital or acquisition expenses can be claimed against any potential gains – thereby reducing the tax paid.

The following link covers this topic:

https://www.ato.gov.au/Individuals/Investing/Keeping-good-investment-records/

Electronic copies of records/invoices are fully acceptable by the ATO.