UK tax explained: the 60% trap and how to save tax

What is the £100,000 tax trap?

Once your income passes £100,000, your tax-free Personal Allowance of £12,570 is withdrawn at £1 for every £2 you earn above it. It disappears completely once you reach £125,140.

Losing that allowance means that, on top of the 40% higher rate you already pay, another slice of your income becomes taxable too. Between £100,000 and £125,140 your marginal rate, meaning the tax on your next £1, rises above 60%, and reaches about 62% once National Insurance is added. It is the highest tax band most employees will ever face, and it is easy to miss because no tax table lists a "60% rate".

This is the trap the calculator is built to show. Bringing your income back under £100,000, usually with a pension contribution or a Gift Aid donation, restores the lost allowance. That can be worth far more than the amount you put in.

Effective rate versus marginal rate: what is the difference?

Your effective rate is the share of your whole income that goes in tax and National Insurance. It is a useful headline number. Your marginal rate is what you pay on your next £1 of income.

The two can be very different, and it is the marginal rate that matters for decisions. Someone earning £110,000 might have an effective rate of roughly a third but a marginal rate of 62%. Every extra £100 of salary then adds only about £38 to their take-home, while £100 put into a pension can save far more than £38 in tax.

How to save tax legally in the UK

You cannot change the tax rates, but you can change how much of your income is exposed to them. Here are the main levers for a UK employee, all of them modelled by the calculator.

Pension contributions reduce the income that is taxed. In the £100,000 to £125,140 trap they are especially powerful, because they can restore your Personal Allowance as well as save tax at your marginal rate.

There is a limit on how much you can pay in and still get tax relief. The Annual Allowance is £60,000 a year across all your pensions. On top of that, relief on contributions you make yourself stops at whatever you earn, or £3,600 a year if that is more, so a low earner can still pay in £3,600. Contributions made by salary sacrifice are treated as your employer paying in, so what you earn does not limit them at all.

The Annual Allowance itself shrinks for very high earners. It starts to reduce only when your income is above £200,000 on one measure and above £260,000 on another, and it never falls below £10,000. Both measures count income from every source, so the calculator can warn you that this may apply but cannot work it out for you.

Salary sacrifice means giving up salary for a pension or a benefit such as an electric car. It also saves National Insurance, which an ordinary pension contribution does not.

Sacrificing a bonus into a pension avoids tax and National Insurance on money you might not miss, and can keep your income below a threshold such as £100,000.

Gift Aid donations extend your basic-rate band and, like pensions, reduce the income that counts towards the £100,000 taper. That gives higher-rate and additional-rate taxpayers extra relief to claim.

You can also claim higher-rate relief. If you pay into a personal pension (relief at source), only 20% is added automatically, so higher-rate and additional-rate taxpayers must claim the rest back from HMRC. Many never do.

How Income Tax and National Insurance work

In England, Wales and Northern Ireland the first £12,570 is tax-free (the Personal Allowance). Income is then taxed at 20% up to £50,270 (the basic rate), 40% from £50,270 to £125,140 (the higher rate), and 45% above £125,140 (the additional rate).

Employee National Insurance is charged at 8% between £12,570 and £50,270, and 2% on everything above. These thresholds are frozen, so as wages rise more income is dragged into the higher bands over time. That is one reason effective rates keep creeping up.

The three ways a pension can be taken

All three save you tax, but they do not save the same tax, and your payslip decides which one you have.

Salary sacrifice reduces your gross pay itself. Because the money never counts as your salary, you pay neither Income Tax nor National Insurance on it. That is why it saves more than the other two.

Net pay leaves your gross pay unchanged but takes the contribution before Income Tax is worked out. You save Income Tax at your highest rate, but National Insurance is still charged on the full amount.

Relief at source is paid out of your take-home pay, and your provider claims 20% back from HMRC and adds it to your pot. If you pay tax above the basic rate, that automatic 20% is not the full relief you are owed. You have to claim the rest from HMRC yourself, and many people never do.

Salary sacrifice, and why it saves more

Salary sacrifice means giving up part of your salary in exchange for something else, such as a pension contribution, an electric car, extra holiday or a cycle-to-work scheme. The swap happens before tax and National Insurance are worked out, so the money is never treated as your pay.

That is the whole advantage. An ordinary pension contribution saves Income Tax but not National Insurance, while a sacrifice saves both. There is one limit worth knowing: your sacrifices together cannot take your pay below the minimum wage.

Benefits in kind are taxed differently

A benefit in kind is something your employer gives you instead of cash, such as a company car or private medical cover. It is taxed like extra salary, so it raises your Income Tax bill.

The difference is National Insurance. On most benefits, including a company car and medical cover, you pay none at all, because your employer pays it instead. That is why a benefit can be worth more to you than the same value in salary. A few things that look like benefits are treated as pay, such as vouchers you can exchange for cash and shares you can sell straight away, and those do carry National Insurance.

Benefits still count towards the income used for the £100,000 allowance taper, so a large benefit can push you into the trap without your salary changing at all.

Student loan repayments

A student loan repayment is not a tax, but it leaves your pay in the same way and it changes what you actually keep. You repay a fixed percentage of the amount you earn above your plan threshold, not of your whole salary. The amount used is the same one your National Insurance is worked out on, so salary sacrifice reduces what you repay while an ordinary pension contribution does not.

Because it stacks on top of Income Tax and National Insurance, it raises your marginal rate. For someone already in the higher-rate band, each extra £1 earned can be worth noticeably less than the headline rates suggest.

Why your payslip may not match this calculator

This calculator works out your position for a whole tax year. Your payslip is worked out one pay period at a time, and the two do not always agree along the way.

Income Tax catches up by itself. Payroll recalculates your position from the start of the year every single time you are paid, so a month that looks wrong corrects itself later. A pay rise, a bonus or a change of tax code moves when you pay, not how much you pay by the end of the year.

National Insurance does not work that way. Each pay period stands on its own and is never revisited, so it really can differ from a yearly calculation. For steady pay the difference is a few pence a year. For a large bonus paid in a single month it can be a few hundred pounds, because most of that one month sits above the monthly upper earnings limit where the rate drops to two per cent. The effect disappears once you earn more than about fifty thousand pounds, since your pay is above that limit every month anyway.

Leaving a job part way through the year usually means you have paid too much. Your tax-free allowance is spread evenly across the year, so stopping work early leaves part of it unused. That money is not always refunded automatically, and it is worth checking with HM Revenue and Customs.

If the gap lasts all year rather than settling down, your tax code is the usual reason. You can enter it under Options on the calculator and we will compare it with the tax-free pay we would expect, then tell you roughly what any difference is worth.

Tax rules that depend on your family

Three rules look at your household rather than just your salary, and each has a threshold worth knowing about.

The High Income Child Benefit Charge claws back Child Benefit once one parent earns above £60,000, and takes all of it by £80,000. It is assessed on the higher earner alone, not on the couple combined.

Tax-Free Childcare and funded childcare hours stop completely once either parent goes a single pound over £100,000. This is a cliff rather than a taper, so a small pay rise can cost far more than it pays. Reducing the income that counts, usually with a pension contribution, restores the whole thing.

Marriage Allowance works the other way, and helps couples where one person earns very little. If one of you earns less than the Personal Allowance, that person can transfer £1,260 of it to the other, provided the other is a basic-rate taxpayer.

Scotland is different

Scotland sets its own Income Tax and has six bands instead of three: a 19% starter rate, 20% basic, 21% intermediate, 42% higher, 45% advanced and a 48% top rate. National Insurance is the same across the UK.

Because National Insurance is set for the whole UK but the bands are not, the two fall out of step, and that creates an odd stretch of income. Scottish higher-rate tax of 42% starts at £43,663, but National Insurance stays at 8% until £50,270. Between those two points your next £1 is taxed at 50%, which then eases to 44% once you pass £50,270. It is the only place in the UK tax system where earning more can briefly become less rewarding, then more rewarding again.

That means Scottish taxpayers reach higher marginal rates sooner, and the £100,000 Personal Allowance trap is even sharper, with the marginal rate inside it approaching 70%. The calculator switches to the correct Scottish bands when you choose Scotland.