Why was my Christmas bonus taxed so much? UK bonus tax explained (2026/27)

A UK bonus is taxed through PAYE in the month it is paid, alongside your salary. It often looks heavily taxed because it sits on top of your pay and takes your highest rate, plus student loan and pension. Usually the sums are right; sometimes the tax code is not.

How PAYE taxes a bonus

There is no special bonus tax. With a normal cumulative code such as 1257L, payroll adds the bonus to your pay so far this tax year (from 6 April) and compares it with your tax-free allowance and the 20% and 40% bands to date. In 2026/27 the first £12,570 is tax-free, then 20% applies on the next £37,700, 40% up to £125,140 and 45% above (England, Wales and Northern Ireland; Scotland has its own bands). Because the bonus sits on top of your salary, all of it is taxed at your highest rate. A December payslip is month 9 of the tax year.

Why it looks like 40% or more

If your salary already puts you in the higher rate band, every pound of bonus takes 40% tax. Add 2% National Insurance, 9% student loan and your pension percentage, and half the bonus can disappear. A smaller bonus can also tip a basic rate earner into 40% for part of it. The real problem case is a non-cumulative code (W1, M1 or X after the number): the bands are applied to that month alone, so a large bonus can be overtaxed. Between £100,000 and £125,140 your allowance shrinks by £1 for every £2 of income, an effective rate of 60% plus NI. PAYE usually does not apply that taper on its own; HMRC collects it through a new code or after the year ends.

National Insurance, student loan and pension

National Insurance is worked out on each pay period on its own. For category A in 2026/27 you pay 8% on monthly pay between £1,048 and £4,189 and 2% above. A bonus month often pushes pay above £4,189, so much of the bonus pays only 2% NI. Student loan is also per pay period: 9% above your plan's monthly threshold (Plan 2: £2,448.75), 6% for postgraduate loans. If the bonus is pensionable, your usual percentage comes off; check your scheme rules.

Sacrificing a bonus into your pension

Many employers let you swap all or part of a bonus for an employer pension contribution (bonus sacrifice). The sacrificed amount carries no income tax and no NI, and some employers add their NI saving. HMRC only accepts it if you agree before you are entitled to the bonus, so the choice usually has to be made in the bonus window, not after the payslip. For people near £100,000, it can also bring income back below the taper. From April 2029, NI relief on pension salary sacrifice is capped at £2,000 a year.

A worked example, what to check and April

Roughly: on £60,000 a year with a £5,000 December bonus, you are already in the 40% band, so the bonus pays £2,000 tax, £100 NI (2%) and, on Plan 2, £450 student loan. You keep about £2,450. Check the code has no W1, M1 or X, that the NI letter is right, that the student loan plan is yours and that the bonus amount matches what you were promised. Payslop checks this for free. On a cumulative code the tax is right for the year and nothing comes back in April. NI is never refunded. Student loan overpaid against your yearly threshold can be reclaimed from the Student Loans Company.

Questions people ask

Related guides

• Your UK payslip explained, line by line (2026/27)
• Your tax code explained: 1257L, BR, 0T and emergency codes

Indicative rules as of October 2026. Not tax or legal advice.