There is no special bonus tax rate. But PAYE does something in a bonus month that makes it look as if there is.
The bonus arrives in your bank account and the number is wrong. Not slightly wrong. Substantially wrong. You were expecting something in the region of £3,500 from a £5,000 bonus. You got £2,700. Or £2,400. Or something else entirely.
This experience is so common that “why is my bonus taxed so much” is one of the most-searched tax questions in the UK every April and May. And the answer, when it finally arrives, tends to produce a mixture of relief and frustration. Relief that there is a logical explanation. Frustration that nobody told you about it beforehand.
There is no special bonus tax rate. There never has been. But the way PAYE works means that a bonus can produce a payslip that looks as if there is.
Your bonus is taxed at your marginal rate. But PAYE does not always know what your marginal rate is until the year is over.
The PAYE Monthly Calculation Problem
PAYE calculates your Income Tax monthly. Each month, your employer looks at that month’s earnings, annualises them — treats them as representative of the full year — and deducts the corresponding tax.
In a normal month, this works smoothly. Your salary is consistent, the annualised figure is accurate, and the monthly deduction is correct.
In a bonus month, it breaks down. Suppose you earn £3,000 per month (£36,000 per year) and receive a £5,000 bonus in March. Your March earnings are £8,000. Annualised: £96,000. PAYE calculates the tax due on £96,000 and deducts accordingly. The deduction looks nothing like your normal monthly tax bill.
By April, however, the cumulative PAYE system has corrected itself. Your total earnings for the year are £41,000. The total tax deducted should equal the correct annual amount. If you were overtaxed in the bonus month, you typically receive a correction in April or in your final payslip.
The shock comes from looking at a single month in isolation rather than the full-year picture. The tax is not wrong. The timing is temporarily distorted.
When It Is Not Just Timing
The PAYE correction applies when your annual income stays within a single tax band. When a bonus pushes your earnings across a threshold, the additional tax is permanent — not a timing difference.
Crossing £50,270: income above this is taxed at 40% rather than 20%. If your salary is £48,000 and your bonus is £5,000, £2,730 of the bonus sits above the threshold. That £2,730 is taxed at 40% rather than 20% — an additional £546 that would not have arisen without the bonus.
Crossing £100,000: the Personal Allowance taper begins, creating an effective 60% rate. A salary of £95,000 and a bonus of £10,000 means £5,000 of the bonus sits in the taper zone. The effective tax on that £5,000 is 60%. See our article on the £100,000 trap for the full explanation.
A worked example:
Salary: £95,000. Bonus: £10,000. Total: £105,000.
£5,000 of the bonus is in the normal higher rate band. Tax: £2,000.
£5,000 of the bonus is in the PA taper zone. Effective tax: £3,000.
Total additional tax on the bonus: £5,000. Effective rate on the bonus as a whole: 50%.
Without the bonus, marginal rate on the last pound of salary: 40%. The bonus pushes income into a more expensive zone.
National Insurance on Bonuses
National Insurance adds another layer. NI is also calculated monthly — and the NI treatment of a bonus depends on whether it pushes monthly earnings above the Upper Earnings Limit.
The Upper Earnings Limit in 2026/27 is £50,270 per year — or £4,189 per month. Below this, employee NI is 8%. Above it, employee NI is 2%.
If your monthly salary is £3,000 and your bonus is £8,000, your total monthly earnings are £11,000. The portion between the Primary Threshold (£1,047/month) and the Upper Earnings Limit (£4,189/month) is taxed at 8%. The portion above £4,189 is taxed at 2%. You will pay 2% NI on a significant portion of the bonus rather than 8% — which is actually more favourable than the standard rate.
The NI calculation does not correct cumulatively in the same way that Income Tax does. What happens in the bonus month is what happens, full stop.
Salary Sacrifice and Bonuses
If your employer offers salary sacrifice, and specifically allows sacrifice of bonus payments, a pension contribution from your bonus is worth serious consideration.
Sacrificing your bonus into a pension eliminates Income Tax at your marginal rate, eliminates employee NI, and reduces your Adjusted Net Income — which matters significantly if the bonus is pushing you toward or into the £100,000 PA taper zone.
The effective relief for someone whose bonus pushes them into the taper zone is 60% — the combined effect of tax relief and restored Personal Allowance. A £10,000 bonus sacrifice costs £4,000 in forgone take-home pay and delivers £10,000 into the pension.
Not all employers permit bonus sacrifice elections, and the window for making the election is typically before the bonus is paid. It requires planning rather than retrospective action. But for those in or near the taper zone, it is the single most impactful thing that can be done with a bonus.
The Bottom Line
The shock on the bonus payslip is almost always either a temporary PAYE timing difference that corrects by April, or the genuine cost of crossing into a higher tax band. It is not a special bonus rate, an error, or an injustice — even when it feels like all three.
- 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. Seek independent advice from a qualified financial adviser before making any financial decisions. When you invest, your capital is at risk. WageLab is not FCA regulated.
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