How GST works in Australia

GST on a standard taxable supply is 10%. Adding GST to an exclusive price is straightforward: multiply by 1.1. Taking GST out of an inclusive price is not “10% of the total”.

If a $100 item has GST added, the customer pays $110. The GST inside $110 is $10, which is one eleventh of the inclusive amount. Taking 10% of $110 would overstate the tax by a dollar.

Some groceries, medical services and education are GST-free. Most residential rent is input-taxed. The GST calculator only models the standard 10% rate.