How Bonus Tax Works in the UK — And Why Your Payslip Looks Wrong

The Myth: "Bonuses Are Taxed at a Higher Rate"

This is one of the most common misconceptions in UK personal finance. Your bonus is not taxed at a special "bonus rate." It is subject to exactly the same income tax bands and National Insurance rates as your regular salary.

The reason your payslip looks like you're being hammered is how PAYE calculates tax monthly — and it all gets corrected at year end.

How PAYE Calculates Monthly: The Annualisation Problem

PAYE works on an annualised basis. Each month, your employer takes your gross pay for that month, multiplies it by 12, and calculates what your full year's tax would be on that annualised figure. Your monthly tax is then one-twelfth of that total.

In a normal month with no bonus, this works perfectly — 12 × your regular salary = your actual annual salary. But when a bonus lands in a single month, the calculation goes like this:

• Your regular monthly salary: £3,500
• Bonus received this month: £5,000
• Total gross this month: £8,500
• PAYE annualises: £8,500 × 12 = £102,000
• Tax is calculated as if you earn £102,000 annually — pushing you into higher bands
• You're only taxed on one month (£8,500 ÷ 12 of the annual bill), but the rate used is based on a much higher bracket

Worked Example: £42,000 Salary + £5,000 Bonus (April)

The payslip shows dramatically higher tax, making it look like the bonus is being taxed at a 40%+ rate. But it isn't. The actual tax on the £5,000 bonus portion, at the correct annual rate, is around £1,000–£1,200 depending on which band it falls in.

Year-End Reconciliation: How You Get the Overpayment Back

Because PAYE accumulates across the year, the over-deduction in the bonus month is corrected in subsequent months. In the months after the bonus month, your annualised income returns to normal (£42,000), and PAYE uses up the tax credit from overpayment in the bonus month. Your subsequent months will show lower than usual tax deductions until the year balances out.

If you leave a job or the tax isn't corrected within the year, HMRC will issue a P800 tax calculation after the year end showing any overpayment — which will be refunded automatically or credited to your next tax year.

Bonus and Student Loan Repayments

This is where things can catch people out. Student loan repayments are deducted in the same way as PAYE — your bonus month's gross is used to calculate the deduction. This means:

• If your annual salary is below the repayment threshold (e.g. £22,000 on Plan 5's £25,000 threshold), you normally make no repayments
• But if your bonus takes your gross in that month above the equivalent monthly threshold, a deduction is made
• If your total annual income for the year remains below the threshold, you can reclaim the overpayment from HMRC or SLC after the year end

Bonus Into the £100,000–£125,140 Trap Zone

If your salary is around £90,000–£100,000 and you receive a bonus that takes your annual income into the Personal Allowance taper zone, the tax consequences are real and permanent — not just a PAYE timing issue. You face an effective 60% marginal rate on income in the £100,000–£125,140 band.

In this situation, you can ask your employer to divert some or all of the bonus into your pension (if they offer this) rather than taking it as cash. This keeps your adjusted net income below £100,000 and preserves your full Personal Allowance.

Can You Time Your Bonus to Pay Less Tax?

Within the tax year, the timing of a bonus payment makes no difference to your total tax bill — PAYE is cumulative and reconciles by 5 April. Across tax years, however, timing can matter: if you are likely to be a basic rate taxpayer this year but a higher rate taxpayer next year (or vice versa), asking for your bonus to be paid in the earlier year could save tax.

Similarly, if you plan to make large pension contributions or gift aid donations this year that will reduce your adjusted net income, receiving the bonus in the same year maximises the benefit of those deductions.