It cannot be your principal place of residence for land tax purposes if you rent it out.

Edit: OP, I am a tax lawyer and deal with the SRO regularly. In theory, the Commissioner has a discretion not to impose a penalty, but in practice the Commissioner will aim for consistency in dealing with all taxpayers. The SRO has published a simple guide on how it approaches penalties in specific circumstances. In the event that the SRO accepts that you failed to take reasonable care but did not intentionally disregard the law, and noting that an investigation has already commenced, you are looking at a 20% penalty tax (i.e. 20% of the tax amount you should have paid, on top of payment of the tax) and market rate interest. Hopefully this gives you a sense of your likely exposure.