£100k tax trap calculator 2026/27
Above £100,000 of adjusted net income, your taxable income less pension contributions and Gift Aid, you lose £1 of personal allowance for every £2 over, and childcare support stops. See what each extra £1 costs you, the pension contribution that gets you back under, and what it does to your take-home, student loan, childcare support and Child Benefit.
| Without | With | Change | |
|---|---|---|---|
| Take-home, after loan repayments | £65,114 | £62,214 | −£2,900 |
| Into your pension | £0 | £10,000 | +£10,000 |
| Income tax | £33,428 | £27,428 | −£6,000 |
| National Insurance | £4,210 | £4,010 | −£200 |
| Student loan repayments | £7,248 | £6,348 | −£900 |
| Personal allowance | £7,579 | £12,579 | +£5,000 |
| Adjusted net income | £110,000 | £100,000 | −£10,000 |
Each £1 into your pension costs you 29p of take-home. Take-home falls by £2,900 a year (about £242 a month); your pension gains £10,000; £5,000 of personal allowance comes back.
This year's cash: −£2,900 take-home = −£2,900, with £10,000 in your pension for later.
What else this changes
Each card is the difference between the two columns aboveRepayments fall to £6,348 a year, because they are worked out on pay after sacrifice. Enter your balance to see what that does to when it is cleared. Payoff projection →
Tax-Free Childcare and England's funded hours stop when either parent's adjusted net income is over £100,000. Add children in paid childcare to see what getting under the line is worth.
If you get Child Benefit, the charge takes all of it above £80,000 of adjusted net income, and this contribution leaves you above that, so the charge would not change. Enter your children on the take-home calculator to see it.
£50,000 of this year's allowance left. Unused allowance from the previous 3 years can be carried forward.
£5,000 of allowance comes back as adjusted net income drops to £100,000, under the line, saving £6,000 of income tax in all.
Salary sacrifice lowers your contractual pay. Some employers base death-in-service cover, sick and maternity pay and bonuses on the lower figure, and some lenders use it for mortgage affordability. Payroll can say how yours is treated. Childcare eligibility is reconfirmed every 3 months on expected income.
Methodology and assumptions
Adjusted net income is your taxable income less gross pension contributions and Gift Aid with the basic-rate tax added back. Between £100,000 and £125,140 the personal allowance falls by £1 for every £2, so each extra £1 is taxed at 40% and, by losing 50p of allowance, makes another 50p taxable at 40%: 60p in all, plus NI and any student loan. Every contribution method lowers adjusted net income £1 for £1, so the contribution needed is what you are over the target by. We run the take-home calculation twice, as now and with the contribution, and every card is the difference. Childcare support is valued from your provider's own prices: the funded hours are worth the gap between the unfunded and funded bills after any top-up, and Tax-Free Childcare adds 20% of what you still pay, within its caps.
What this cannot know
Whether your employer offers salary sacrifice or bonus sacrifice, and what else they base on contractual pay. Unused pension allowance from earlier years. Your partner's exact income (only whether it is over the line). Providers' local funding rules and whether they offer stretched hours. Wales tests childcare on gross income and is not modelled; Scotland's hours are not income-tested.
Questions people ask
Why does each extra £1 cost 62p or more?
The taper alone makes it 60%. National Insurance adds 2%, and a Plan 2 loan another 9%, so 71% of each extra £1 can go before it reaches you.
Does the contribution have to be a pension?
No: Gift Aid donations also reduce adjusted net income, grossed up by the basic rate. Enter them on the take-home calculator and they carry here.
What if a bonus takes me over mid-year?
Childcare eligibility is checked every 3 months on your expected income for the whole year, so a bonus that pushes expected adjusted net income over £100,000 ends it for that quarter. Sacrificing the bonus into your pension on its payday keeps it out of expected income, if your employer offers that.