Bonus Tax UK 2025/26: Why Your £5,000 Bonus Feels Like £2,500

Quick answer

A UK bonus is taxed at your normal marginal rate for that income slice — there's no special "bonus tax". But a one-off lump sum often pushes you into a higher tax band for that period, plus NI and student loan apply on top, which is why bonuses feel painful.

For a typical UK higher-rate taxpayer earning £55,000, an extra £5,000 bonus:

• Income tax (40%): £2,000.
• Employee NI (2%, since over UEL): £100.
• Student loan (9% Plan 2): £450.
• Pension auto-enrolment 5%: £250.
• Net take-home from bonus: £2,200.

That's a 56% deduction. Not punitive in rate-of-tax terms, but enough to feel like half of it disappeared.

The PAYE quirk — why bonus months look weird

UK PAYE is cumulative — each pay period, the system calculates "given your YTD income, how much tax should you have paid YTD?".

For a one-off bonus, the system temporarily projects your annual income upward, often pushing you into higher tax bands. That month's deductions can look extreme. Subsequent months automatically reconcile downward.

Worked example — Sarah, £42,000 salary + £8,000 March bonus

In March (final tax year month), Sarah's payroll calculates:

• YTD pay before bonus: £38,500.
• Add March bonus £8,000 = £46,500 YTD income.
• Annualised for cumulative PAYE: still falls in basic rate, no special crossing.

But what if the bonus is paid early in the year, in May:

• YTD pay through May (2 months at £3,500/month = £7,000) + £8,000 bonus = £15,000 YTD by end of May.
• PAYE projects annual: £15,000 × 12/2 = £90,000 annualised.
• That month, deductions calculated as if she were on £90,000 — higher-rate.
• Lots of tax deducted from May pay.
• Then June, July, etc. her actual pay (£3,500/month) catches up.
• The system gradually refunds the over-collection through later months.

By 5 April (year end), Sarah's total deductions match her actual £50,000 annual income (£42k + £8k bonus). The PAYE system has self-corrected.

Practical impact: large early-year bonuses look brutal that month. End-of-year bonuses look more normal. Total annual tax is the same either way.

Worked examples — bonus by salary level

For a £5,000 bonus on different base salaries (excluding pension and student loan):

The £100k-£125k band is uniquely brutal — bonus income there has an effective tax+NI rate of 62%.

The £100,000-£125,140 trap

Between £100,000 and £125,140 of adjusted income, your personal allowance tapers — £1 lost for every £2 earned.

Effect on a £5,000 bonus pushing you from £100,000 to £105,000:

• Income tax on bonus at 40%: £2,000.
• Plus PA taper: £2,500 of allowance lost, equivalent to extra £1,000 of tax.
• Plus NI 2%: £100.
• Total tax on bonus: £3,100.
• Net keep: £1,900 out of £5,000.

This is why high earners with bonuses are aggressively recommended to salary-sacrifice into pension when their income approaches £100k.

Worked example — Mark, £105,000 salary, £20,000 bonus

Without pension sacrifice:

• Bonus £20,000 fully in the taper band.
• Total tax + NI on £20,000: ~£12,400 (62% effective).
• Net keep: £7,600.

With £20,000 sacrificed to pension:

• Adjusted income drops to £105,000 (where it was without bonus).
• PA restored fully.
• No bonus impact on take-home.
• £20,000 added to pension pot.

The sacrifice option creates £20,000 of pension wealth at zero cost of net pay. For high earners with bonuses, this is the textbook play.

Student loan impact

Student loan plans deduct 9% on income above the threshold (or 6% for postgraduate loans):

A £5,000 bonus pushed someone earning £40,000 well above each threshold:

• Plan 2: 9% × £5,000 = £450 SL deducted.
• Combined with income tax (£1,000) + NI (£400) = £1,850.
• Net bonus: £3,150.

For someone on multiple plans (Plan 2 + PGL = 9% + 6% = 15%) the loan deduction alone is £750.

Salary sacrifice — bonus version

Many employers offer bonus sacrifice — instead of receiving the bonus as cash, you can:

• Sacrifice some or all of it into your pension.
• Receive it as enhanced contributions to a Cycle to Work scheme.
• Convert to an EV salary sacrifice scheme top-up.

Why bonus sacrifice is more powerful than salary sacrifice

A bonus is single-event income, so:

1. You can sacrifice 100% of the bonus into pension (vs typical 5-15% of regular salary).
2. The tax/NI saving is at your highest marginal rate for that period.
3. You can use it to escape band crossings without affecting your regular take-home.

Worked example — Lisa, £55k salary, £10k bonus, sacrifices 80%

• Cash bonus: £2,000 (20% of £10k).
• Pension contribution: £8,000.
• Tax saved on £8,000 sacrifice (40% IT + 2% NI = 42%): £3,360.
• Lisa keeps £2,000 cash + £8,000 in pension at cost of £8,000 - £3,360 = £4,640 net.
• Compare to taking all as cash: £5,800 net (after £4,200 tax).

Lisa effectively gets a £8,000 pension boost for a £1,160 net pay sacrifice (£5,800 - £4,640) compared to taking all cash.

When you can't sacrifice

Some employers don't offer bonus sacrifice; some have restrictive rules. Check with HR before the bonus is paid — once it's paid, the tax position is locked.

What about commission?

Sales commission follows the same rules as bonus. Treated as employment income, taxed at marginal rate. PAYE may handle it more smoothly if it's regular monthly rather than annual lumps.

What about share awards / RSUs?

UK employee share awards (RSUs, share options, ESPP) are mostly taxed as employment income when they vest:

• Income tax at marginal rate on the vest value.
• NI on the vest value.
• Subsequent capital gain when sold = CGT on the difference between vest value and sale value (above the £3,000 exemption).

Tax-advantaged share schemes (SAYE / SIP) have specific rules — generally more favourable than ordinary RSUs.

Common errors

1. Assuming bonus is taxed at a special rate — it isn't.
2. Panicking at a bonus-month payslip — the cumulative PAYE system reconciles.
3. Not realising bonus pushes into the £100k taper trap — biggest pitfall for high earners.
4. Forgetting student loan applies to bonuses — adds 9% to the effective deduction.
5. Not exploring bonus sacrifice — biggest missed opportunity for higher earners.

Try the numbers

For income tax band visualisation:

Sources

• HMRC: Income Tax rates and Personal Allowances
• HMRC: PAYE: how it works
• HMRC: Tax on employee share schemes
• gov.uk: Student loan repayments
• HMRC: Salary sacrifice and the effects on PAYE