How we verify

1. Every rule in a tool comes from an official source (a law, a tax authority page, an official form) and the tool page names that source and the date it was last updated.
2. We read official sources every day; when a rate, threshold, form or deadline changes, the tool is updated and the page date moves.
3. Calculators are tested against worked examples with known results before they go live; a tool that fails its own examples is not published.
4. Dates and facts we publish outside our site (posts, extensions, packages) are re-read from the source at the moment we publish them.
5. Our tools apply published rules; they are not tax or legal advice. For your own case, the official source on the page is the final word.

Found an error? Tell us — we correct it and date the correction.