How we calculate
Where our numbers come from, and how we keep them right.
Built from official sources
Every calculator is built from the rates, thresholds and rules published by the government agency responsible: state and territory revenue offices for stamp duty, and the Australian Taxation Office for income tax. Each calculator lists the exact pages it uses under "Sources".
Tested against official examples
Before a calculator goes live, we run it against the worked examples the agency publishes and against independent test cases at every threshold. For example, our Queensland calculator reproduces the Queensland Revenue Office's own example of a $730,000 first home, which pays $6,555.
Rounding
We apply the same rounding the agency uses. Queensland, for instance, charges duty "for each $100 or part of $100", so any part of $100 is rounded up before the rate is applied.
Keeping it current
We re-check every calculator when state budgets are announced, when the new financial year starts on 1 July, and whenever an agency announces a change. The "last checked" date on each page tells you when we last confirmed the rules.
What calculators can't do
Calculators assume a straightforward purchase. They can't fully model shared ownership, trusts and companies, mixed-use land, or eligibility questions that need a judgement call. Where that matters, each page says so.
Found an error?
Email [email protected] with the page and the numbers you used. We fix confirmed errors as a priority.