Key takeaways
- Your bonus was not taxed at 40% because bonuses have a special rate — PAYE looked at one month's pay and assumed you earn that every month.
- Over the full year, a £2,000 bonus on a £35,000 salary is taxed at your normal marginal rate, and the extra tax usually comes back by April.
- PAYE is cumulative, so a month that overpays is followed by months that underpay, and by 5 April the total is normally right.
- If your salary plus bonus genuinely takes you over £50,270 for the year, the slice above that line really is taxed at 40%.
Your bonus was not taxed at 40% because bonuses have a special rate. PAYE looked at one month's pay, assumed you earn that every month, and taxed that month as if your salary were much higher. The extra tax usually comes back by April.
It is one of the most common payslip shocks in Britain. Your salary is £35,000, your bonus is £2,000, and the payslip shows a tax deduction that looks like 40% on the bonus. Nothing is wrong with your tax code, and bonuses are not taxed at a special rate. What happened is a quirk of how PAYE works month by month — and understanding it saves you a panicked call to payroll.
How PAYE sees your bonus month
PAYE (Pay As You Earn) does not know your annual salary. Each month it looks at what you were paid that month, multiplies it by 12, and works out the tax as if that were your annual pay. In a normal month on £35,000, your monthly gross is £2,916.67, and the tax works out at 20% on the slice above your monthly personal allowance. In your bonus month, your gross jumps — say to £4,916.67 — and PAYE annualises that to £59,000. At £59,000, part of your pay falls into the 40% band, so that month's tax is calculated with some 40% in it.
Your employer has not made a mistake. HMRC designed PAYE this way because it has to work for people whose pay genuinely changes month to month — overtime, commission, irregular hours. The system assumes the spike is permanent, taxes it accordingly, and then corrects itself in later months when your pay returns to normal.
The numbers: a £2,000 bonus on a £35,000 salary
Over the full tax year, a £2,000 bonus on top of a £35,000 salary is taxed at your normal marginal rate — 20% income tax plus 8% National Insurance, with a little extra pension. Here is the annual picture, worked out by the take-home pay calculator with auto-enrolment pension at 5% of qualifying earnings:
| £35,000 salary | £35,000 + £2,000 bonus | Difference | |
|---|---|---|---|
| Gross pay | £35,000.00 | £37,000.00 | £2,000.00 |
| Pension (5% of qualifying earnings) | £1,438.00 | £1,538.00 | £100.00 |
| Income tax | £4,198.40 | £4,578.40 | £380.00 |
| National Insurance | £1,794.40 | £1,954.40 | £160.00 |
| Take-home pay | £27,569.20 | £28,929.20 | £1,360.00 |
Over the year, your £2,000 bonus adds £1,360.00 to your take-home pay — £380.00 of income tax (19% of the bonus, because £100 went to pension first) and £160.00 of National Insurance. But in the bonus month itself, the payslip can easily show £700 or £800 of extra tax, because PAYE taxed that month as if you earned £59,000 a year. The difference — roughly £300 to £400 — comes back in the following months, when your pay is back to normal and PAYE's cumulative calculation catches up.
Why it corrects itself (usually)
PAYE is cumulative. Each month, your employer adds up everything you have earned so far this tax year, works out the tax due on that total, and subtracts what you have already paid. So a month that overpays is followed by months that underpay, and by 5 April the total is normally right. The correction is automatic — you do not need to claim it.
There are two exceptions. First, if the bonus lands in March, the last month of the tax year, there are no later months to correct it in — but the tax year's final calculation still happens, and any overpayment is repaid, usually automatically through your tax code the following year or by a refund from HMRC. Second, if you change jobs mid-year, the cumulative chain breaks and a small over- or underpayment can linger until HMRC reconciles your record after the year ends.
When a bonus really is taxed at 40%
Sometimes the 40% is real, not a PAYE quirk. If your salary plus bonus genuinely takes you over £50,270 for the year, the slice above that line is taxed at 40%. On a £50,000 salary, a £2,000 bonus pushes £1,730 over the higher-rate threshold (after pension), and that slice really is 40%. And above £100,000 the personal allowance taper makes the effective rate 60% on a slice of income — a bonus there can look brutal, and that part does not come back. Use the take-home pay calculator with your own salary to see which case you are in: if your annual total stays under £50,270, the 40% is a timing effect, not a real rate.
What about National Insurance on a bonus?
Income tax is only half the story. National Insurance is charged on your bonus month's pay too, and it annualises in the same way — but with a twist that usually works in your favour. Employee NI is 8% on pay between £12,570 and £50,270 a year, then 2% above, and it is worked out per pay period: in your bonus month, the monthly thresholds are £1,048 and £4,189. On a £35,000 salary your normal monthly pay of £2,916.67 sits comfortably inside the 8% band, and a £2,000 bonus pushes the month to £4,916.67 — just over the £4,189 upper threshold. So a small slice of your bonus month's NI is charged at 2% instead of 8%, which slightly reduces the NI on the bonus compared with the annual picture. Over the year it evens out: the annual NI on the bonus is £160.00, exactly 8% of £2,000, because your annual pay of £37,000 never crosses £50,270. The monthly wobble is real but small, and it corrects itself the same way the tax does.
The same logic applies to your pension, but in the opposite direction. Auto-enrolment pension is 5% of your qualifying earnings — the band from £6,240 to £50,270 — and a bonus inside that band increases your pension by £100.00 on a £2,000 bonus. That is money going into your pension pot, not money lost: your take-home pay is £100 lower, but your retirement savings are £100 higher, plus your employer's 3% on the same slice. If your bonus takes you over £50,270, the qualifying-earnings band caps out and no further pension is due on the excess — another reason the annual picture is kinder than the bonus month suggests.
Bonuses and the £100,000 taper
There is one situation where a bonus really does cost you far more than 20%, and it is worth knowing before you accept it. Above £100,000, you lose £1 of personal allowance for every £2 you earn, so between £100,000 and £125,140 your effective income-tax rate is 60% — 40% tax plus 20% from the lost allowance — before National Insurance and student loan. A £5,000 bonus in that zone can cost £3,000 in income tax alone, plus 2% NI and 9% student loan if you have a Plan 2 loan: a marginal rate of 71% on the bonus. Nothing about that comes back in later months, because it is the annual position, not a PAYE timing effect. If you are anywhere near £100,000, ask whether the bonus can be paid into your pension instead: pension contributions made through salary sacrifice reduce the income counted for the taper, so a sacrificed bonus can dodge the 60% band entirely. The take-home pay calculator shows the taper warning and the marginal rate at any salary — run your own figure before bonus season, not after.
What to do about it
Mostly, nothing. Check the payslip: your tax code should be the same as usual (1257L for most people), and the bonus should appear as a separate line. If the code changed, that is a different problem — see our guide to 1257L and when your tax code is wrong. If the over-deduction has not corrected itself two or three months after the bonus, call HMRC or check your Personal Tax Account — but give it those months first, because the cumulative system needs them. And if your employer offers salary sacrifice, putting the bonus into your pension instead can be worth asking about: pension contributions come off before income tax, so a sacrificed bonus escapes the 40% month entirely.
One more thing to check: student loans. A bonus is charged for student loan at 9% above your plan threshold, just like salary, and the same PAYE annualising can make the loan deduction spike in the bonus month. It corrects the same way.
The short version
Your bonus is taxed at your normal rate over the year. PAYE just pretends, for one month, that you will earn that much every month — and that pretence is what makes the payslip look like 40%. Give it a few months, and the money comes back.
Check your own bonus
See what a bonus really leaves you — work out your own bonus before bonus season, not after.
Figures from the 2026/27 rates, last checked against GOV.UK on 5 November 2026. See all the rates on UK tax rates 2026/27. Next in this series: Two jobs? How tax codes BR and D0 really work.