Despite owning multiple properties, you cannot simply choose which property is your main residence to suit the best capital gains tax outcome at the time of sale.  In order to claim the Main Residence Exemption from CGT at the time of sale there is a need to establish the property as your main residence. 

Generally speaking, your main residence is considered to be the address at which you most frequently reside and is that recorded:

• on the Electoral Role;
• on your driver’s licence;
• with the ATO; and
• with your bank.

The existence of an electricity account and internet account in your name for the address and even photos of you residing at the property can also help establish a property as your main residence.