Stamp duty (now called 'transfer duty' in most states) is a one-off state government tax paid on the purchase of property. Rates and thresholds vary widely between Australian states and territories — this calculator implements the current scale for every state, including the first-home-buyer concession that applies in most of them. Enter the property value and state, tick first-home-buyer if it applies, and the calculator returns the duty payable plus the concession amount.