Consider this situation:

- residential investment property, probably negatively geared for a few years

- considering renovations and then renting again for a few years

- probably move in eventually

- once used as a principal place of residence (PPOR), is there any liability for capital gains tax?

The short answer is Yes.

This is a misunderstood area of tax law.   It has been an investment property since acquisition.   Even if it was vacant for some time it was not at that time a PPOR either.

Even if it was a PPOR for some time, and being the only property used as a principal residence, it does not matter how long you stay in it, there will be some assessable gain for the time it was not a principal residence.   This is because it was an investment when acquired and no time as your principal residence removes this.

You need records of the purchase price and all monies spent on the property, so that the capital gain can be calculated and the gain apportioned between the periods of investment and home.

The reverse situation is that if may have been purchased as a principal residence but you moved out at some future time.   The property is then rented.   If you move back in within six years of moving out and still eventually sell, there is no taxable capital gain or apportionment required.   If you don't move back in, it is an apportionment situation once again.

As you would expect, the rules are fairly complex.   Always check; knowing is better than hoping.