Methodology & sources

How our calculators work, where the numbers come from, and their limits.

Principles

• Official sources first. Rates and thresholds come from the ATO, SRO Victoria, Fair Work Ombudsman and ASIC Moneysmart.
• Show the working. Each calculator lists its formula and a worked example you can reproduce by hand.
• Tested. The calculation code is checked against hand-worked examples (50 automated checks) before each release.
• Dated. Figures were last checked on 29 Oct 2026 and apply to the 2026–27 financial year (1 July 2026 to 30 June 2027).

Known simplifications

• Tax calculators assume Australian residents for tax purposes and don't cover every offset or levy (for example the Medicare levy surcharge).
• The stamp duty calculator covers Victoria only and excludes foreign purchaser duty, off-the-plan and pensioner concessions and registration fees.
• The mortgage calculator uses monthly compounding; lenders calculate daily.

Primary sources

• ATO: Tax rates for Australian residents
• ATO: Super guarantee
• ATO: Study and training loan repayment thresholds and rates
• ATO: Rental expenses you can claim
• SRO Victoria: General land transfer duty rates
• SRO Victoria: PPR current rates
• Fair Work Ombudsman: National Employment Standards
• ASIC Moneysmart: Mortgage offset accounts

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