How Bonuses Are Taxed in the UK — and Why Your Payslip Looks Wrong

Why a bonus month shows a high deduction

When a bonus is paid in a single month, payroll adds it to that month's gross pay and calculates income tax as if you were earning that amount every month. This can push the month's pay into a higher tax band, triggering what looks like an unusually high deduction — even though your annual calculation will often result in a refund or lower deductions later.

The PAYE cumulative system corrects itself across the tax year. If April has an unusually high bonus, later months will collect less tax to compensate once cumulative income settles into the right band. By the end of the tax year, the total tax deducted should align with your actual annual income.

If you receive a bonus and leave the job shortly afterwards, or if you're on a non-cumulative (W1/M1) tax code, the correction mechanism does not apply and you may need to claim a refund via self-assessment or HMRC's online refund process.

• Bonus month tax is annualised: treated as if every month paid that amount.
• Cumulative PAYE corrects the over-deduction in later months.
• Non-cumulative codes (W1/M1) do not self-correct — manual refund required.
• Bonuses over £12,570 annual equivalent push income into higher bands.

National Insurance on bonuses

National Insurance on a bonus follows the same monthly calculation logic as income tax. The primary threshold and upper earnings limit are applied monthly, so a large bonus in one month may attract 8% NI on more of the payment than your normal salary does. Unlike income tax, NI has no annual reconciliation — what is deducted in the bonus month is not corrected in later months.

This means bonuses are sometimes taxed at a higher NI effective rate than your regular salary if the monthly figures push earnings above the lower earnings limit more dramatically. For a bonus received on top of an already-high salary, the NI deduction is capped at 2% above the upper earnings limit.

The absence of NI correction across the year is a reason why total NI can look slightly different from a simple annual calculation.

• NI is calculated monthly with no annual reconciliation.
• A large bonus can attract 8% NI on more income than usual.
• Above the upper earnings limit (£50,270/year), NI rate drops to 2%.
• No automatic refund mechanism for NI — only income tax corrects itself.

Planning around bonus payments

If your employer offers the choice of timing a bonus payment, receiving it at the start of the tax year gives the cumulative system the most time to self-correct. Receiving a bonus in March — the final payroll month — means almost no time for correction, potentially leaving you with a higher effective deduction for that year.

Pension salary sacrifice on a bonus can reduce both income tax and NI significantly. If your employer allows, sacrificing part of the bonus directly into pension before tax is calculated can be more efficient than contributing from net pay afterwards.

If you leave employment shortly after a bonus, submit a P50 or use the HMRC refund claim system to recover any overpaid income tax from the bonus month.

• Early tax year bonuses give PAYE more time to self-correct.
• Salary sacrifice on the bonus reduces both tax and NI in one step.
• Leaving employer after bonus: claim overpaid tax via P50 or HMRC account.
• Use a calculator to model net-pay impact before bonus month.