The £100,000 Tax Trap for High Earners: How It Works and How to Plan Around It

The Tax Band That Officially Does Not Exist

Most successful professionals assume that the more they earn, the more they keep. They believe this because they are:

• Working hard for promotions and pay rises
• Treating a bonus as money earned and money kept
• Assuming the tax system is broadly proportionate
• Confident that there is no tax rate higher than the 45% additional rate

For income up to £100,000, that holds true. Just above it, something stranger happens.

There is a stretch of income, between £100,000 and £125,140, where the effective tax rate is not 40%, and not 45%, but around 60%. It is not printed on any tax table. It has no official name. Yet for a growing number of UK earners, it is very real, and it can make a hard-won pay rise feel almost pointless.

What makes the trap frustrating is how invisible it is. It does not appear on a payslip as a line item, and it does not arrive as a bill. It simply shows up as a pay rise that did not feel like one, or a bonus that seemed to shrink somewhere between the announcement and the bank account. Many people sense that something is wrong without ever identifying what.

This article explains what the £100,000 tax trap is, how it works, who it now catches, and the legitimate steps that may ease it. None of this involves anything aggressive or artificial. It is about understanding a quirk of the rules and planning around it sensibly.

How the £100,000 Trap Actually Works

The trap is not a separate tax band. It is a side effect of the way the personal allowance is withdrawn.

Every taxpayer normally has a personal allowance, currently £12,570, which is the amount of income that can be earned before any income tax is due. Once adjusted net income rises above £100,000, that allowance is gradually taken away.

The mechanism is simple, and unforgiving:

• For every £2 of income above £100,000, £1 of personal allowance is lost
• The full £12,570 allowance is therefore gone by the time income reaches £125,140
• In that £25,140 band, you are taxed on the income itself, and taxed again on the allowance you are losing

Here is why that produces an effective 60% rate. On an extra £100 of income in this band, you pay 40% income tax on the £100, which is £40. You also lose £50 of personal allowance, and that £50 becomes taxable at 40%, which is a further £20. So £60 of an extra £100 disappears in tax. Once employee National Insurance is added, the effective rate is higher still.

The word effective matters. There is no 60% line in the legislation. The 60% is simply what the arithmetic produces when a normal tax rate and a disappearing allowance are combined. But the money is real, and so is the effect on take-home pay.

Illustrative example. Suppose someone earning £100,000 receives a £10,000 pay rise. Across that £10,000, income tax takes around 40%, and the gradual loss of personal allowance adds a further effective charge on top, so a large part of the rise never reaches their take-home pay. The gross figure on the payslip rises clearly. The amount that actually arrives in their account rises by far less. The figures depend on individual circumstances, but the pattern inside this band is consistent: the gap between gross pay and net pay is unusually wide.

Who Is Being Caught, and Why the Numbers Are Rising

When the £100,000 threshold was introduced, it affected a relatively small group of very high earners. That is no longer the case.

The threshold has not risen for many years. Salaries, meanwhile, have. The result is a steady widening of the trap, even though the rule itself has not changed. This effect, often called fiscal drag, pulls more people into the band each year simply because pay rises while the threshold stands still.

The scale is now significant. According to HMRC forecasts, more than 2 million people are expected to be affected by the £100,000 tax trap in the 2026/27 tax year, the highest number on record. Many of them are not who most people picture when they hear the phrase high earner. They are senior managers, experienced professionals, specialists and people whose pay has simply grown over a career.

There is also a behavioural cost. Some people in this band conclude that additional work, a promotion or a bonus is barely worth having, because so little of it reaches them. That is an understandable reaction. It is also one that planning can often address, because the effective rate is not fixed in stone for everyone.

It is worth being precise about what fiscal drag does and does not mean. The rule has not become harsher. The roughly 60% effect has existed for as long as the taper has. What has changed is the number of people standing in its path. A salary that felt comfortably clear of £100,000 a decade ago may now sit inside the band, through no decision of the earner’s own. That is why the trap increasingly affects people who would never describe themselves as wealthy.

The Hidden Cost for Parents: Childcare

For working parents, the £100,000 figure carries a second, often larger, sting that has nothing to do with income tax rates.

Eligibility for several forms of government childcare support depends on neither parent having an adjusted net income above £100,000. These include Tax-Free Childcare and the funded childcare hours available to working families.

This creates what is sometimes called a cliff edge. Unlike the gradual personal allowance taper, childcare support can be lost in full once income crosses £100,000. In practice, that means a modest pay rise of a few hundred pounds can, for a family using significant childcare, cost far more than it delivers, once the lost support is taken into account.

Illustrative example. A parent with adjusted net income just below £100,000 receives a pay rise of a few hundred pounds. That small rise takes them over the threshold, and the family loses access to Tax-Free Childcare and funded hours. For a household with one or two children in paid childcare, the value of that lost support can run well beyond the pay rise itself. The exact figures depend on the childcare used and the ages of the children, but the direction is clear. Close to this threshold, a small rise can leave a family worse off in cash terms.

The important point is this. Because the test is based on adjusted net income, the same step that can ease the personal allowance taper, a pension contribution, can also help a parent stay below the childcare threshold. For families with young children, the childcare effect is often the larger of the two, and it deserves to be part of the calculation rather than discovered by accident.

What Can Be Done: Pension Contributions

The single most relevant tool for the £100,000 trap is the pension contribution, because of how the threshold is measured.

The taper is based on adjusted net income, not gross salary. Adjusted net income is, broadly, your total taxable income, reduced by certain things, including personal pension contributions and Gift Aid donations. A personal pension contribution therefore reduces the figure used to test the personal allowance.

The effect can be considerable. A contribution that brings adjusted net income from above £100,000 back down towards, or below, that level can restore some or all of the personal allowance. Because the income being moved was effectively taxed at around 60%, the relief on that contribution is unusually valuable. In simple terms, money that would largely have gone in tax is instead going into your own pension.

Illustrative example. A person with adjusted net income of £110,000 who makes a personal pension contribution of £10,000 reduces the figure used for the taper to £100,000, which can restore the full personal allowance. The money has moved from income, where much of it faced the roughly 60% effective rate, into a pension held for their own retirement. The arithmetic is appealing. Whether it is the right choice still depends on whether that £10,000 can genuinely be spared, and whether locking it away until later life suits the rest of the plan.

There are important conditions, and they are not optional caveats:

• The money is going into a pension, so it is tied up until at least the normal minimum pension age
• Contributions must be affordable and consistent with your wider financial plan
• There are limits on how much can be paid into a pension with tax relief each year
• For very high earners, the tapered annual allowance can reduce those limits further, which is a specialist area

This is why a pension contribution to address the £100,000 trap should be a considered decision, not a reflex. It can be highly effective, but only where it also fits your retirement plans and your cashflow. Understanding how it interacts with the wider picture of how much you are saving for retirement is part of getting it right.

Other Levers, and Their Limits

Pension contributions are the main lever, but they are not the only one. Each of the others has limits worth understanding.

Gift Aid donations also reduce adjusted net income, in the same way as pension contributions. For people who already give to charity, making sure those gifts are recorded correctly can have a useful side effect on the personal allowance calculation.

Bonus timing can matter. Where there is genuine flexibility over when a bonus is paid or how it is structured, spreading income across tax years rather than concentrating it can sometimes reduce how much falls into the trap. This depends entirely on what your employer allows, and should never drift into anything artificial.

Salary sacrifice into a pension has long been a common route for higher earners, because it can also save National Insurance. This is changing. From April 2029, the National Insurance advantage of salary sacrifice into a pension will be capped, with only the first £2,000 sacrificed each year remaining free of National Insurance. The income tax position is not the same as the National Insurance position, but anyone relying heavily on salary sacrifice should be aware that one part of its value is being reduced.

It is also worth knowing what does not help. Increasing ISA contributions, for example, is sensible saving, but ISA contributions do not reduce adjusted net income, so they have no effect on the personal allowance taper. The same is true of most ordinary investment decisions. Only a small number of specific things, chiefly pension contributions and Gift Aid, actually move the figure the taper is measured against. Knowing the difference avoids effort being spent in the wrong place.

The common thread is that every lever has conditions. None of them works the same way for everyone, and the way these decisions interact with your longer-term plan is what determines whether they actually help.

Used together and reviewed in good time, these levers can meaningfully soften the trap. Used in isolation, or discovered too late in the tax year, they often cannot. The difference is rarely the cleverness of any single step. It is whether the whole position was looked at early enough to act on it.

Why Timing and Planning Matter

The £100,000 trap is unusually sensitive to timing, because it resets every tax year.

• The personal allowance taper is calculated on each tax year separately
• Pension contributions generally need to be made within the tax year to affect that year
• A bonus paid in March falls into a different position from one paid in April
• Childcare eligibility is also assessed against income, so the same timing affects it

This means the trap rewards people who plan ahead and quietly penalises those who do not. Someone who reviews their expected income partway through the tax year still has time to act. Someone who discovers the problem when their tax position is finalised has usually run out of room.

None of this requires complicated arrangements. For many people it is simply a matter of knowing, in advance, roughly where their income will land, and deciding deliberately what to do about it before the tax year closes.

There is one more reason timing matters. Income is not always predictable. Bonuses, commission, dividends and one-off payments can push a year’s total higher than expected. Building in a margin, and reviewing the position before the tax year ends rather than after, is what turns the trap from something that happens to you into something you have planned for.

How Professional Planning Support Actually Fits

For UK high earners, professional planning tends to be most valuable when it does the following.

• Establishes clearly where your income sits relative to the key thresholds
• Models the real effect of the taper, and of childcare loss where it applies
• Tests whether a pension contribution genuinely fits your retirement plan and cashflow
• Coordinates the timing of income, bonuses and contributions across the tax year
• Keeps the wider picture in view, so a tax decision does not quietly distort everything else

For people with variable pay, this is rarely a one-off exercise. Income shifts from year to year, the thresholds stay frozen, and rules such as the salary sacrifice change in 2029 alter the picture over time. A position that was handled well in one tax year may need revisiting in the next.

The aim is not simply to reduce a tax bill. It is to make sure that the steps taken to do so also make sense for your retirement, your family and your wider goals.

This is why high earners often seek a structured conversation rather than a quick fix.

The Soft But Decisive Next Step

If you are reading this and thinking:

• My pay has gone up, but my take-home pay has not moved as much as I expected
• I am not sure how much personal allowance I am actually losing
• A bonus is coming, and I do not know what it will do to my position
• We may be losing childcare support and I had not connected it to my income

then the next step is usually a structured conversation focused on clarity, not implementation. The £100,000 trap is far easier to plan for than to unpick after the event, and the tax year is a real deadline. Seeing the numbers clearly, while there is still time to act, is the whole point.

Final Takeaway

The £100,000 tax trap is not about:

• A penalty for success that nothing can be done about
• Aggressive or artificial tax avoidance
• Turning down pay rises to stay below a line

It is about:

• Understanding a genuine quirk in how the personal allowance is withdrawn
• Knowing the real effective rate on income between £100,000 and £125,140
• Recognising the separate, and often larger, effect on childcare support
• Using pension contributions and timing deliberately, where they fit your plan

Most people only notice the trap when a pay rise underwhelms them. Those who understand it in advance can make calm, deliberate decisions, and often keep far more of what they have earned.