Sources & Methodology
The official sources we rely on, the methods behind our calculators, and how we keep everything reviewed.
PurchaseWise provides property calculators and educational guides for Australians researching property, mortgages and buying costs. This page explains the official sources we rely on, the methods behind our calculators, and the review process that keeps them current.
Our content is designed to help users understand common property and mortgage topics. It is general information only, not personal financial, legal, tax or credit advice.
Our Approach
We aim to create practical, easy-to-understand content using:
- Standard mortgage repayment and amortisation formulas
- Standard deposit, loan-amount and loan-to-value-ratio calculations
- Verified general transfer-duty rate schedules from official state and territory revenue offices
- Publicly available government and regulatory information
- Practical Australian property industry experience from our publisher
- Worked examples that show each step
- Editorial review before publication
Official Australian Sources We Refer To
Where relevant, PurchaseWise refers to publicly available Australian government and regulatory sources. These include the following:
ASIC MoneySmart
Australian Government financial guidance on mortgages, deposits, borrowing and managing money.
Reserve Bank of Australia (RBA)
Official cash rate and monetary policy context that influences home-loan interest rates.
Australian Taxation Office (ATO)
Tax treatment of property, including negative gearing, capital gains tax and deductions for investors.
Housing Australia
Australian Government housing agency administering support schemes such as the First Home Guarantee.
Australian Bureau of Statistics (ABS)
National housing, lending and property price statistics used for context in our guides.
State & Territory Revenue Offices
Stamp duty (transfer duty), concessions, grants and surcharges are set and administered by each state and territory. The official sources below are the authoritative reference for the rules in each jurisdiction, and we recheck our general-rate figures against them.
New South Wales
Revenue NSW
Victoria
State Revenue Office Victoria
Queensland
Queensland Revenue Office
Western Australia
Revenue WA (Department of Finance)
South Australia
RevenueSA
Tasmania
State Revenue Office Tasmania
Australian Capital Territory
ACT Revenue Office
Northern Territory
Territory Revenue Office (NT)
See also our Stamp Duty & First Home Buyer Costs by State resource for a guided overview of each jurisdiction.
Calculator Methodology
Our mortgage-related calculators use standard amortisation formulas with user-provided inputs: loan amount, interest rate, loan term, repayment frequency, deposit amount, purchase price and — where relevant — an extra repayment amount. The output is an estimate based on the inputs entered.
Our stamp duty calculator applies the verified general transfer-duty rate schedule for the selected state or territory and contract date. Concessions, grants and surcharges are not automatically applied to every scenario and may change the duty actually payable — which is why every result directs users to confirm with the relevant revenue office.
Our calculators do not access lender systems, credit files, bank approval policies or live loan pricing. They cannot confirm borrowing capacity, loan approval, exact stamp duty, mortgage insurance or final settlement costs. Full formula detail and worked examples are on the How Our Calculators Work page.
How We Keep Calculators and Guides Reviewed
Property and finance information changes over time. PurchaseWise keeps its content current through a documented review process:
- Mortgage and LVR formulas are reviewed against standard Australian lending practice at least annually.
- Stamp duty rates and concessions are rechecked against official state and territory revenue office publications as they are added, and on the review date shown on each calculator.
- Guides show a "last reviewed" date so readers can see how current the information is.
- When a material change is announced (for example a state-budget stamp duty change or a first-home buyer scheme update), the affected guide or calculator is reviewed and updated promptly.
- Reader-reported errors submitted through the Contact page are investigated by the responsible publisher and corrected where confirmed.
Formula review date: September 2026. See Publisher Information for who is responsible for this process.
Use of Examples
Many PurchaseWise guides include worked examples to make concepts easier to understand. Examples may use rounded numbers such as a $500,000 loan amount, a $750,000 or $1,000,000 purchase price, a 20% deposit scenario, a low-deposit buyer scenario, a first-home buyer scenario and an investor scenario.
These examples are illustrative only. They are not recommendations, and the exact figures a lender or revenue office calculates for your situation may differ.
Changing Information
Property and finance information can change. This includes:
Users should always confirm current information with the relevant government authority, lender, broker, accountant, solicitor, settlement agent or qualified adviser.
Editorial Standards
Our editorial standards are set out on the Editorial Policy page. In short: content is written in plain English, calculations use clearly stated assumptions, advertising does not determine results, and corrections are made when errors are confirmed.
PurchaseWise does not provide financial advice, legal advice, tax advice, credit advice or investment advice. Our calculators and guides are intended for general education only and may not account for every personal circumstance or all costs involved in a property purchase or loan.
Our Goal
Our goal is to help Australians understand the numbers, compare scenarios and become better prepared before speaking with a professional or making a major property decision — with free, transparent tools and clearly sourced information.