INCOME TAX · 2026/27
The £100,000 Trap
How the UK tax system turns a raise into a pay cut — and what to do about it
16 min read · Updated June 2026
In £100,000 is a lot of money. Let us be clear about that from the start. You are in the top 5% of UK earners. You almost certainly own your home. You have a good pension, probably a decent car, and the kind of financial cushion that most people in this country will never experience. Nobody reading this at that salary level should feel hard done by.And yet. The UK tax system does something at £100,000 that is genuinely extraordinary — and genuinely unfair. It imposes an effective marginal tax rate of 60% on every pound earned between £100,000 and £125,140. Not because of some new surcharge on the wealthy. But as the quiet, mathematical consequence of withdrawing a tax-free allowance at precisely the moment when most people stop paying attention to their payslip.
The people it catches are not oligarchs. They are partners at law firms, senior directors at FTSE companies, experienced consultants, GPs who have built a successful practice, finance professionals in their forties who have spent two decades earning their way to a comfortable salary. Wealthy by any reasonable definition. But not the kind of wealthy where you have a team of tax advisers watching your back.
The trap has been there since 2010. It has barely moved. And every year, inflation and wage growth quietly push more people into it.
A 60% marginal tax rate. On people who are already paying 40%. Hidden in plain sight.
The Invisible Mechanism
To understand the trap, you first need to understand something called the Personal Allowance. Every UK taxpayer gets one. It is the amount you can earn before paying any Income Tax at all. In 2026/27, it is £12,570.
For most people, the Personal Allowance is invisible. It just exists, quietly, doing its job. You earn a salary, the first £12,570 is untouched, and everything above it gets taxed at 20%, then 40% above £50,270. Simple enough.
But above £100,000, something different happens. HMRC begins withdrawing the Personal Allowance. The rule is precise: for every £2 of income above £100,000, you lose £1 of allowance. By the time income reaches £125,140, the allowance has been reduced to zero.
This sounds technical. The consequences are not.
Imagine you are earning £100,000. Your next pay rise takes you to £102,000. On that additional £2,000, you owe tax in the normal way — 40%, because you are a higher rate taxpayer. That is £800. But the rise has also cost you £1,000 of Personal Allowance. That £1,000 is now taxable income. At 40%, that is another £400.
Total tax on a £2,000 raise: £1,200. Effective rate: 60%.
The arithmetic of 60%
For every £2 you earn above £100,000:
→ 80p in Income Tax on those £2 (at 40%)
→ 80p more as £1 of Personal Allowance is withdrawn and taxed at 40%
= £1.60 tax on £2 earned. That is 60%.
Compare this to earning £99,999: marginal rate is 40%. At £100,001: instantly 60%. The system does not ease you in gently.
Martin Lewis built a media empire on a single insight: most people are losing money not because they earn too little, but because they do not understand the rules of the financial system they are operating in. The £100,000 trap is a perfect example. The incentive structure it creates is genuinely strange: it discourages earnings in the very range where most professionals are trying hardest to grow.
What the Numbers Actually Say
Abstract percentages are easy to dismiss. Concrete numbers are harder to ignore.
Salary
Personal Allowance
Income Tax
Net Take-Home
£95,000
£12,570
£28,528
£62,211
£100,000
£12,570
£30,528
£65,211
£105,000
£10,070
£32,528
£68,211
£110,000
£7,570
£34,528
£71,211
£115,000
£5,070
£36,528
£74,211
£120,000
£2,570
£38,528
£77,211
£125,140
£0
£40,583
£80,296
£130,000
£0
£42,714
£82,937
Source: WageLab calculator, 2026/27 rates. NI not included. Use the WageLab calculator for your exact figures.
Look at the column on the right. From £100,000 to £105,000 — a £5,000 pay rise — net take-home increases by £3,000. Two thousand pounds of a five thousand pound raise goes to HMRC. That is not a rounding error. That is a structural feature of the tax system.
Now look at what happens past £125,140. The marginal rate drops back to 45%. Which means that, counterintuitively, someone earning £130,000 pays a lower marginal rate on their last pound than someone earning £110,000. The trap has an entrance and an exit, and between the two it is uniquely, unfairly expensive.
The trap has an entrance and an exit, and between the two it is uniquely, unfairly expensive. A pay rise that leaves you worse off. A tax band with a 60% rate that HMRC has never once called a 60% rate.
The People It Catches
There is a tempting assumption that this only matters to a small number of very high earners. That assumption is wrong, and it is getting wronger every year.
The £100,000 threshold was set in 2010. It has never been adjusted for inflation. In real terms, £100,000 in 2010 is worth approximately £150,000 today. The Resolution Foundation estimates that the number of taxpayers caught in the taper has roughly tripled since its introduction.
Who are these people? They are NHS consultants whose salaries have grown with successive pay awards. Senior managers in financial services, law, and consulting who have spent a decade climbing. Engineers and technologists in the companies that now dominate the economy. GPs. Headteachers of large schools. People who have worked hard, saved carefully, and arrived at an income level where the tax system quietly begins to penalise their success.
They are not billionaires. They are not financial sophisticates with teams of advisers and offshore structures. Many of them have no idea the trap exists until they see their first payslip after a raise and wonder where the money went.
There is also the bonus problem. If your base salary is £90,000 and your employer pays you a £15,000 bonus, £5,000 of that bonus falls inside the trap. The effective tax rate on that £5,000 is 60%. A bonus designed to reward performance ends up working rather differently on paper than it does in your bank account.
You can be wealthy and still be paying far more tax than you realise.
The Second Sting — What Else You Lose
The Personal Allowance disappearing is not the only consequence of crossing £100,000. Two other things happen, and both of them can be worth more, in cash terms, than the extra tax itself.
The first is free childcare. England's 30-hour free childcare entitlement for three and four-year-olds requires both parents to have an Adjusted Net Income below £100,000. There is no gradual reduction. No partial benefit. You either qualify or you do not. If one parent earns £100,001, the household loses the additional 15 hours entirely.
Depending on location and provider, those 15 hours are worth somewhere between £6,000 and £8,000 per year. In London, the figure is higher. Think about what that means: a £1 pay rise above £100,000 can trigger a loss of benefit worth thousands of pounds per year. When you add this to the additional tax, the effective cost of earning just above the threshold can be extraordinary.
The second is the Self Assessment obligation. Above £100,000, you must file a tax return every year. This is not financially catastrophic but it is administratively real, and the return is where HMRC will expect you to account for any adjustments to your position. For many people crossing this threshold for the first time, the tax return is the first indication that anything unusual has happened at all.
There is also a quieter consequence: the Child Benefit High Income Charge begins at £60,000 and is fully repaid by £80,000. For households combining the HICBC with the PA taper, the interaction between the two creates effective marginal rates that are difficult to calculate and easy to misunderstand.
Complexity, in tax as in investing, is rarely neutral. It almost always advantages those who understand it and disadvantages those who do not.
The Way Out: Adjusted Net Income
Here is where the story changes.
HMRC does not use your gross salary to determine how much Personal Allowance you receive. It uses something called your Adjusted Net Income — ANI. This is a specific calculation, and it is the key to escaping the trap.
ANI starts with your total income and subtracts certain deductions. The most important of these are pension contributions made through salary sacrifice or a Net Pay Arrangement, the grossed-up value of Gift Aid donations, and Cycle to Work scheme contributions. What remains is your ANI.
If your ANI falls below £100,000, your Personal Allowance is fully restored.
This is not a grey area. It is not aggressive tax planning. It is a feature of the system, deliberately designed to encourage pension saving and charitable giving. Every pound you contribute to a pension in the taper zone does not just benefit from standard 40% tax relief. It also restores allowance. The combined effect is a 60% effective relief rate.
The pension arithmetic in the taper zone
Starting position: Salary £110,000. ANI: £110,000. Personal Allowance: £7,570. Income Tax: approximately £34,528.
After a £10,000 salary sacrifice pension contribution:
New ANI: £100,000. Personal Allowance restored to £12,570. Income Tax: approximately £30,528.
Tax saved: £4,000. Your pension pot grows by £10,000. Your take-home pay falls by £6,000.
Effective relief rate on the pension contribution: 60%.
The question is not whether this is worth doing. It almost certainly is. The question is whether you know about it.
The system, whatever its flaws, is designed to reward exactly the behaviour that escapes it: put money into a pension.
The instrument most commonly used is either a workplace salary sacrifice scheme or a Self-Invested Personal Pension — a SIPP. If your employer offers salary sacrifice, this is usually the most efficient route. The contribution reduces your contractual salary, which means HMRC sees a lower gross income, your ANI falls, and both you and your employer save National Insurance contributions on top of the Income Tax saving.
For those whose employer does not offer salary sacrifice, a personal SIPP contribution still works — the mechanics differ slightly, as Relief at Source contributions are deducted from ANI rather than gross pay — but the outcome is the same. Your ANI falls, your allowance is restored, and the effective relief rate in the taper zone remains 60%.
Gift Aid and the Multiplier Effect
Pension contributions attract the most attention in this conversation, but they are not the only lever.
Gift Aid donations are also deducted from ANI. When you donate cash to a charity under Gift Aid, the charity claims 20% basic rate tax relief from HMRC and adds it to your donation. But the deduction from your ANI is calculated on the grossed-up amount — the donation divided by 0.8.
A £4,000 cash donation under Gift Aid reduces your ANI by £5,000. For someone sitting at £105,000, this brings ANI to £100,000, fully restoring the Personal Allowance. The tax saving — £2,000 from the restored allowance — comes on top of the relief the charity has already claimed.
Think about what this means in practice. You donate £4,000 to a cause you care about. The charity receives £5,000. You save £2,000 in additional Income Tax. The government has effectively contributed £3,000 of your £4,000 donation. Your net cost is £2,000 to generate a £5,000 benefit to the charity.
At any income level, Gift Aid is efficient. In the taper zone, it is extraordinary.
This is not a trick or a scheme. It is precisely what Gift Aid was designed to do: encourage charitable giving by making it financially rational. The fact that the saving is larger inside the taper zone is a consequence of the mechanics, not a loophole.
The Part Nobody Talks About
There is a dimension to this that the tax textbooks do not capture.
Most of the people who fall into the £100,000 trap are not wealthy in the sense of having significant assets or financial flexibility. They earn a good salary. They probably have a mortgage. They may have children. Their income feels comfortable but not abundant, and the idea of voluntarily reducing it — even in exchange for a pension contribution that comes back to them later — can feel psychologically difficult.
This is the tension that Richard Thaler — who won the Nobel Prize for his work on behavioural economics — spent decades documenting: the most financially logical decision is rarely the one people actually make, because we respond to how choices feel, not just what they produce. Redirecting £10,000 of your salary into a pension requires understanding the mechanics, trusting that the money is not lost, and accepting a smaller number on your monthly payslip in exchange for a larger number in a retirement account you cannot touch for years.
Most people find this hard. Not because they are irrational, but because the trade-off is genuinely uncomfortable — and because nobody explained to them that the effective cost of the pension contribution, in this particular income range, is just 40p for every £1 going in.
Knowledge changes decisions. Understanding that a £10,000 pension contribution costs you £6,000 in take-home pay rather than £10,000 is not a minor clarification. It is a fundamental reframing of the choice.
Working It Out for Yourself
The interaction between salary, bonus, pension contributions, Gift Aid, and the PA taper is complex enough that the only reliable way to understand your own position is to model it directly. The variables that matter are:
Your gross salary and any expected bonus. Your pension contribution method — salary sacrifice, Net Pay Arrangement, or Relief at Source — and the rate. Any Gift Aid donations you make regularly. Whether your employer passes on their National Insurance saving from salary sacrifice. And whether your household claims Child Benefit or the 30-hour childcare, which changes the calculus significantly for earnings near the threshold.
The calculator does not replace a qualified financial adviser. But it is the right starting point for understanding the shape of your own situation — and for arriving at that conversation with the right questions already formed.
The Honest Bottom Line
The £100,000 trap is real. It is significant. And it is affecting more people every year as wages rise and the threshold stays frozen.
The 60% effective rate is not a rounding error or an exaggeration. It is the mathematically precise consequence of losing a Personal Allowance while already paying tax at 40%. Combined with the childcare cliff edge, crossing £100,000 can mean that a pay rise leaves you genuinely worse off — not just paying more tax, but losing benefits that were worth more than the raise itself.
But the trap is escapable. The UK pension system was designed to reward exactly the behaviour that escapes it. A £10,000 pension contribution costing £6,000 net is not a sacrifice. It is, in the taper zone, one of the most financially efficient decisions available in the entire UK tax system.
There is an old observation about British culture: we are deeply uncomfortable talking about money, which means most people arrive at important financial decisions with no preparation and no map. The biggest financial advantages tend to go to people who simply know more about how the system works. Not because they are smarter. Not because they earn more. But because they asked the right questions at the right time.
The £100,000 trap is a question worth asking. The answer, once you understand it, is usually straightforward.
Important: This article is for informational purposes only and does not constitute financial or tax advice. Based on 2026/27 HMRC rates which are subject to change. Individual circumstances vary significantly. Seek independent advice from a qualified financial adviser before making pension, salary sacrifice, or tax planning decisions. When you invest, your capital is at risk. WageLab is not FCA regulated.
© WageLab 2026 · wagelab.co.uk
The calculator
Use the WageLab calculator to model exactly how your take-home pay changes as your salary moves through the £100,000–£125,140 zone. Enter a salary of £100,000, then increase it in steps to see the effect on your net pay.
Pay particular attention to:
- The Adjusted Net Income figure shown in the calculator
- The PA taper row in the Allowances tab
- The 60% marginal rate warning that appears when your ANI is in the taper zone
WageLab is not regulated by the FCA and does not provide financial advice. This article is for informational purposes only. Seek independent advice before making financial decisions.