Stamp duty is a state government tax on property purchases. It's one of the largest upfront costs of buying — and unlike your deposit, it can't be borrowed. You need to have it in cash at settlement.
Every state sets its own rates, brackets, and concessions, which is why the numbers vary so wildly depending on where you buy.
The tax that was supposed to disappear. When the GST was introduced in July 2000, state governments signed an intergovernmental agreement committing to abolish a list of "inefficient" taxes — stamp duty on property was explicitly on that list. The deal was straightforward: the Commonwealth hands over all GST revenue, the states phase out the old nuisance taxes in return.
That was 26 years ago. Stamp duty is still here. In the intervening decades it has ballooned into one of state governments' biggest revenue streams — NSW alone collects over $8 billion a year from it. The ACT is the only jurisdiction that has actually started phasing it out, replacing it with a broad-based land tax from 2012. Every other state has quietly shelved the commitment and hopes you've forgotten it was ever made.
You haven't. Now you know.