Key Takeaways
- Your personal allowance of £12,570 starts to reduce once your income exceeds £100,000 – falling by £1 for every £2 you earn above the threshold. This creates the so-called 100k tax trap.
- Income between £100,000 and £125,140 is taxed at an effective 60% marginal rate, rising to 62% once you include National Insurance contributions.
- Making pension contributions via salary sacrifice is one of the most tax-efficient ways to bring your adjusted net income below £100,000 and restore your full personal allowance.
- Earning even £1 over £100,000 can trigger the loss of free childcare entitlements worth up to £20,000 a year for families with young children.
- Gift Aid donations, personal pension contributions and timing of bonus payments can all be used to reduce your adjusted net income before the end of the tax year.
- You are required to file a self-assessment tax return once your income exceeds £100,000, even if all your tax is collected through PAYE.
Table of contents
- 1. What is the £100k tax trap and why does it matter?
- 2. How the personal allowance taper works in practice
- 3. How the £100k threshold affects free childcare and tax-free childcare
- 4. What adjusted net income means and how to calculate it?
- 5. How pension contributions help you avoid the £100k tax trap
- 6. Other strategies to reduce your adjusted net income
- 7. Why earning over £100,000 triggers a Self Assessment tax return?
- 8. Why the £100k tax trap is catching more people every year?
- 9. Getting ahead of the £100k tax trap with the right financial planning
1. What is the £100k tax trap and why does it matter?
The £100k tax trap is a quirk in the UK tax system that creates an effective income tax rate of 60% on earnings between £100,000 and £125,140. It exists because HMRC gradually withdraws your tax-free personal allowance once your adjusted net income crosses £100,000.
For the 2025/26 tax year, the standard personal allowance is £12,570. That is the amount of income you can earn without paying any income tax. Once your total income reaches £100,000, you start losing this allowance at a rate of £1 for every £2 of income above the threshold. By the time your income hits £125,140, your personal allowance has been completely removed.
This matters because the income that was previously sheltered by the personal allowance now becomes taxable at 40%. You are already paying 40% higher-rate tax on income above the basic rate threshold. The taper adds another 20% on top and pushes your marginal rate to 60% on every pound earned between £100,000 and £125,140.
Add in employee National Insurance contributions at 2%, and the real marginal tax rate in this band is 62%. For every extra £100 you earn, just £38 reaches your pocket.
2. How the personal allowance taper works in practice
The personal allowance taper is the mechanism behind the £100k tax trap.
Your personal allowance is reduced by £1 for every £2 of adjusted net income above £100,000. Adjusted net income is your total taxable income minus specific deductions like pension contributions and Gift Aid donations. If your adjusted net income is £110,000, you lose £5,000 of your personal allowance. If it reaches £125,140, you lose the entire £12,570.
The table below shows how the taper plays out at different income levels during the 2025–26 tax year:
| Adjusted net income | Personal allowance lost | Remaining personal allowance | Effective marginal rate |
|---|---|---|---|
| £100,000 | £0 | £12,570 | 40% |
| £105,000 | £2,500 | £10,070 | 60% |
| £110,000 | £5,000 | £7,570 | 60% |
| £115,000 | £7,500 | £5,070 | 60% |
| £120,000 | £10,000 | £2,570 | 60% |
| £125,140 | £12,570 | £0 | 45% |
Once your income passes £125,140, the personal allowance is fully withdrawn and the standard additional rate of 45% applies. The 60% effective band only exists in the £100,000–£125,140 window.
Note: Feel free to check our 👉 Take Home Pay Calculator, where you can see how the 100k tax trap works in real life.
3. How the £100k threshold affects free childcare and tax-free childcare
The financial impact of crossing £100,000 goes beyond income tax. If you have young children, the consequences can be severe… and they hit as a cliff edge rather than a taper.
Loss of 30 hours free childcare
In England, parents can claim up to 30 hours of free childcare a week for children aged nine months to four years for 38 weeks of the year. To qualify, each parent must earn at least the equivalent of 16 hours a week at National Minimum Wage, but no more than £100,000. If either parent earns £1 over the £100,000 limit, the entire entitlement is lost.
Loss of tax-free childcare
Tax-free childcare provides up to £2,000 per child per year (or £4,000 for disabled children). The government tops up 20p for every 80p you pay into a childcare account. Once either parent’s adjusted net income exceeds £100,000, this benefit is also withdrawn.
4. What adjusted net income means and how to calculate it?
Adjusted net income is the measure HMRC uses to determine if your personal allowance should be tapered. It is not the same as your gross salary, and understanding the difference gives you room to plan.
Your adjusted net income starts with your total taxable income for the year. This includes:
- employment income
- self-employment profits
- rental income
- savings interest
- dividends and
- any other taxable sources.
From that total, you deduct specific reliefs that HMRC allows before assessing the taper. The most common deductions include:
- Gross pension contributions made under relief at source (where the pension provider claims basic rate tax relief)
- Trading losses that can be set against general income
- Gift Aid donations (grossed up to include basic rate tax relief)
Salary sacrifice pension contributions work differently: they reduce your gross pay before it is reported to HMRC, so they lower your total income rather than being deducted from it. The effect is the same: a lower adjusted net income.
If your gross salary is £112,000 and you sacrifice £12,000 into a pension, your adjusted net income drops to £100,000. (Assuming no other income pushes adjusted net income back above.) Your full personal allowance is restored and you escape the 60% band entirely.
5. How pension contributions help you avoid the £100k tax trap
Making pension contributions is regarded as the most effective way to reduce your adjusted net income and escape the 60% trap. The tax relief you receive in this band is extraordinarily generous compared to normal rates.
Salary sacrifice
Under salary sacrifice, you agree with your employer to give up part of your salary or bonus in exchange for an employer pension contribution. Your gross pay is reduced before tax and National Insurance are calculated. This means you save income tax, employee NI and – in many cases – your employer saves employer NI too.
Some employers pass their NI savings into your pension as an additional contribution.
If you earn £110,000 and sacrifice £10,000, your taxable income falls to £100,000. Your full personal allowance is restored.
Keep in mind that from April 2029, the government plans to cap the NI exemption on salary sacrifice pension contributions at £2,000 per year. Contributions above £2,000 will still receive full income tax relief but will no longer save National Insurance.
Personal pension contributions
If salary sacrifice is not available through your employer, you can still get pension tax relief by making personal contributions. Under the relief-at-source system, your pension provider automatically adds 20% basic-rate tax relief, and higher-rate taxpayers can usually claim the additional relief through Self Assessment.
If you pay £8,000 net into a pension, the provider adds £2,000, making a gross contribution of £10,000. That full £10,000 is deducted from your adjusted net income for taper purposes.
Pension Contribution Limits
You can contribute up to £60,000 per year across all pension contributions (the annual allowance for 2025–26) or 100% of your relevant UK earnings, whichever is lower. If you have unused annual allowance from the previous three tax years, you may be able to carry it forward to make a larger contribution in the current year.
6. Other strategies to reduce your adjusted net income
Pension contributions are not the only tool available. Several other approaches can bring your adjusted net income below the £100,000 mark.
- Gift Aid donations: Donate £4,000 net to charity (grossed up to £5,000 with basic rate relief) to reduce adjusted net income by £5,000.
- Defer bonuses: Shift March bonuses to April to keep this year’s income under £100,000.
- Salary sacrifice: Use for pensions, cycle-to-work, or electric car schemes to lower gross pay.
7. Why earning over £100,000 triggers a Self Assessment tax return?
Once your income exceeds £100,000, HMRC requires you to file a Self Assessment tax return – even if all your tax is collected through PAYE and you owe nothing further.
This is a legal obligation, not optional!
The self-assessment return is how HMRC recalculates your personal allowance based on your actual income for the year.
The deadline for online self-assessment returns is 31 January following the end of the tax year. If you need to register for self-assessment for the first time, you must do so by 5 October after the end of the tax year in which your income first exceeded £100,000. Missing either deadline triggers automatic penalties.
8. Why the £100k tax trap is catching more people every year?
The £100,000 personal allowance threshold has not changed since it was introduced in April 2010. Over 15 years of wage growth, inflation and fiscal drag have pulled hundreds of thousands more taxpayers into the trap.
The freeze on income tax thresholds – in place since April 2021 and now extended to at least April 2028 – is the main driver. The basic rate threshold, higher rate threshold and personal allowance are all locked at their current levels. As salaries rise with inflation, more workers cross the £100,000 mark.
For UK creative professionals (designers, photographers, agency owners, film directors, etc.) income can change from year to year.
9. Getting ahead of the £100k tax trap with the right financial planning
The £100k tax trap is one of the most punitive features in the UK tax system, but it is also one of the most manageable.
The common thread across every mitigation strategy is adjusted net income. Reduce it below £100,000 and the taper disappears, your personal allowance is restored and – if applicable – your childcare entitlements are protected.
At WallsMan Creative, we specialise in accountancy for creative businesses across the UK. If your income is approaching or has crossed £100,000 and you want to make sure you are not paying more tax than you need to, our team can help you structure your finances, plan your pension contributions and your tax year with confidence.
