Sources Policy

This page explains where our figures come from and how we choose them.

We prefer primary, official sources

For tax and government rules we use the relevant authority directly: HMRC and GOV.UK for the UK, the Ontario Ministry of Finance and the City of Toronto for Canadian land transfer tax, and the ATO for Australia. We link to these sources on the tools that use them so you can verify the figures yourself.

How source data is recorded

The figures behind each calculator — bands, thresholds, allowances, typical prices — are stored in editable data files, separate from the calculation code. Each file records the tax year or review date it relates to and a note that the figures must be verified before being relied on.

Material prices and estimates

For home-project costs, official sources don’t exist in the same way, so we use representative market figures and label them clearly as editable defaults. These vary by region and supplier, and we encourage readers to adjust them to local quotes.

When sources disagree or change

Rules sometimes change part-way through a year, and sources occasionally contain errors. When we become aware of a change, we update the data and the last-reviewed date. If a figure is contested or uncertain, we err on the side of caution and say so on the page.