How we check our numbers
People use our calculators to plan real decisions, so getting the numbers right is the most important thing we do. This page explains where our figures come from and how we keep them current.
Where the figures come from
Tax rates, thresholds and benefit rules come from official sources: government tax authorities (such as HMRC, the IRS, the Canada Revenue Agency, the Australian Taxation Office, Inland Revenue New Zealand, the UAE Federal Tax Authority and ZATCA in Saudi Arabia), published legislation, and official labour-law texts. Each calculator page links to the sources it relies on.
How we keep them current
Every calculator states the tax year or rules it uses and the date we last checked them. We review figures when they change, which for most of our countries happens at predictable times:
- United Kingdom: after the Budget, and before the tax year starts on 6 April.
- United States: when the IRS publishes the next year’s inflation adjustments, usually in October or November.
- Canada: when the CRA publishes indexed brackets in November, and before 1 January.
- Australia: after the Federal Budget, and before the income year starts on 1 July.
- New Zealand: after the Budget, and before the tax year starts on 1 April.
- VAT, GST and labour-law rules: whenever a change is announced.
How the calculators are tested
Before a calculator goes live we check its results against worked examples from the official source, or against the authority’s own calculator where one exists, at several income levels. The guide under each tool repeats a worked example so you can check the method yourself.
Simplifications
Real tax affairs can include allowances, credits and special cases that a quick calculator can’t cover. Where a tool leaves something out, the page says so. Results are estimates to help you plan; for decisions about your own situation, check with the official source or a qualified adviser.
Corrections
If you think something is wrong, tell us. We investigate every report, fix confirmed errors quickly, and update the “last checked” date on the page.
How we write
We use software, including AI writing tools, to help draft guides and build calculators. A person reviews every page, and all figures are checked against the sources above before publishing. Advertisers have no influence over our content.