Methodology · AU-HOME-018
How the Property Buying Costs Calculator works
This page documents how the Property Buying Costs Calculator produces its figures: the engines and formulas it runs, the rule packs it reads statutory values from, the official documents those packs cite, and how the engines are verified. Official sources were last retrieved on .
Engines and formulas
- E08 · Property transaction engine
General transfer duty as bracket base plus rate per $100 or part thereof, from per-state rule packs. Unsupported states block rather than guess.
Registered formulas: §12.8 duty brackets
Rule packs
Statutory values come only from versioned, hash-verified rule packs citing official sources. Current status of the packs this calculator can use:
- au-stamp-duty-nswactive · v0.1.0
- Transfer duty - current thresholds and ratesRevenue NSW · retrieved 2026-08-20
- au-stamp-duty-vicactive · v0.1.0
- Land transfer duty — non-principal place of residence (general) current ratesState Revenue Office Victoria · retrieved 2026-08-21
- au-stamp-duty-qldactive · v0.1.0
- Transfer duty ratesQueensland Revenue Office · retrieved 2026-08-20
- au-stamp-duty-waactive · v0.1.0
- Transfer duty assessment — general rateRevenueWA (Department of Treasury and Finance) · retrieved 2026-08-21
- au-stamp-duty-saactive · v0.1.0
- Rate of stamp duty (conveyances)RevenueSA · retrieved 2026-08-21
- au-stamp-duty-tasactive · v0.1.0
- Property transfer duties - rates of dutyState Revenue Office Tasmania · retrieved 2026-08-20
- au-stamp-duty-actactive · v0.1.0
- Conveyance duty for non-commercial property — not an eligible owner occupierACT Revenue Office · retrieved 2026-08-21
- au-stamp-duty-ntactive · v0.1.0
- Stamp Duty Act 1978, Schedule 1 cl 1 (conveyances) — as in force at 1 July 2025Northern Territory of Australia (legislation.nt.gov.au) · retrieved 2026-08-21
- Official conveyance duty calculator script (rounding convention)Northern Territory Government (nt.gov.au) · retrieved 2026-08-21
Verification
Engines carry boundary tests at every bracket edge, property-based tests, reconciliation invariants and, where official worked examples exist, tests that reproduce them exactly. The full source register is on the sources page.