About
effectivetax.co.uk is a free UK take-home calculator with a single focus: showing you your real marginal and effective tax rate, and the moves that lower it.
Its flagship is the £100,000–£125,140 “tax trap”, where losing your Personal Allowance pushes your marginal rate above 60% — and where a pension contribution or Gift Aid donation can claw it back.
What it models
Income tax for England, Wales, Northern Ireland and Scotland; National Insurance; pensions (net pay, salary sacrifice and relief at source, with the higher-rate relief you can reclaim); student loans (Plans 1, 2, 4, 5 and postgraduate); benefits in kind; Gift Aid; bonuses; and generic salary sacrifice — all on current 2026/27 rates.
How accurate is it?
The calculation engine is checked against HM Revenue & Customs’ own PAYE estimator to the penny across 180+ captured scenarios, and every figure the site shows comes straight from that verified engine.
Not financial advice
This tool gives estimates to help you understand your position — it is not financial or tax advice. Always check the numbers against HMRC and, for decisions that matter, speak to a qualified adviser.