£100k tax trap calculator
Is the trap 60%, 62% or 71%? All three are quoted by authoritative sources, and none is wrong: they just count different deductions. 60% is income tax alone, 62% adds the 2% National Insurance, and a Plan 2 student loan takes it past 70%. Rather than pick a headline, this calculator computes the tax on one more pound of your income and reports the rate you actually face.
Your exact marginal rate at £115,000
62.0%
Of the next £100 you earn, £38.00 reaches your pocket. We measure this by actually computing the tax on £1 more, not by quoting a headline figure.
The marginal rate, salary by salary
| Salary | Marginal rate | Next £100 is worth |
|---|---|---|
| £95,000 | 42.0% | £58.00 |
| £100,000 | 62.0% | £38.00 |
| £105,000 | 62.0% | £38.00 |
| £115,000 | 62.0% | £38.00 |
| £125,140 | 47.0% | £53.00 |
| £130,000 | 47.0% | £53.00 |
Check what the same income does to childcare and Child Benefit →
Why does the £100k tax trap exist?
Above £100,000 of adjusted net income the personal allowance is withdrawn at £1 for every £2 earned. Each extra pound is therefore taxed at 40% and pulls 50p of previously tax-free income into 40% tax, 60% combined, before National Insurance. The taper ends at £125,140, where the allowance is exhausted and the marginal rate falls back to 47%, making this the only place in the UK system where earning more is taxed above the additional rate itself. And the tax is not the worst of it: the same £100,000 line is a cliff edge for childcare: one pound of adjusted net income over it forfeits free childcare hours and Tax-Free Childcare entirely, a loss that can exceed £5,000 a year for a family with two children in nursery. The escape route for both is the same: salary sacrifice or a pension contribution that brings adjusted net income back under the line.
What does the trap cost in total?
Crossing the whole taper, earning £125,140 instead of £100,000, means £25,140 of extra gross pay of which roughly £15,587 goes in tax and National Insurance at the 62% effective rate: you keep about £9,553. That is why salaries between £100,000 and £125,140 are where large pension contributions make the most arithmetic sense in the UK, the taper means the state funds most of them. The withdrawal itself follows from the personal allowance rules on gov.uk's “Income over £100,000” guidance, and the thresholds are on our rates reference with their HMRC sources.
2026/27 rates, checked 2026-08-28. The marginal rate is measured by computation, not quoted, the engine and its test anchors are described on the about page.