A plain-English explainer on understanding your tax code, linked to the published UK tax rules and primary GOV.UK and HMRC sources behind it.
Primary source: Tax codes (GOV.UK).
This guide explains understanding your tax code in plain English, written against the published UK tax rules rather than summarised from memory. It links to the rules it relies on, so the figure behind each statement can be checked directly.
Where a rate or threshold has changed, the guide points to the effective date and the GOV.UK or HMRC publication that carries it. The guide is informational only and does not take account of an individual's circumstances.