Bonus Tax Calculator
✓ Verified for 2026/27Bonus Tax Breakdown
How We Calculated This
- Marginal Tax Band Assessment: The calculator evaluates your current base salary and identifies your highest marginal tax rate for the 2026/27 tax year. Since your standard Personal Allowance of £12,570 is typically allocated to your primary base salary, your bonus does not benefit from this tax-free threshold and is taxed entirely at your highest marginal rate (e.g., 20% basic, 40% higher, or 45% additional).
- Pension Salary Sacrifice (Bonus Sacrifice) Calculation: If you participate in a workplace bonus sacrifice scheme, you can choose to divert a percentage (from 0% up to 100%) of your gross bonus directly into your occupational pension pot. This amount is subtracted from your gross taxable bonus before any tax or National Insurance calculations are applied, representing an exceptionally powerful method of tax mitigation.
- Marginal Income Tax Calculation: The remaining taxable portion of your bonus (gross bonus minus pension sacrifice) is stacked on top of your base salary. The calculator applies the standard 2026/27 progressive income tax rates: 20% for taxable income within the basic rate band (up to £50,270), 40% for the higher rate band (£50,271 to £125,140), and 45% for the additional rate band (above £125,140). It also models the £100,000 personal allowance taper, where your £12,570 allowance is reduced by £1 for every £2 of adjusted net income exceeding £100,000, creating an effective 60% marginal tax rate.
- Employee National Insurance Contributions (Class 1 NICs): Employee National Insurance is calculated on a non-cumulative basis per pay period (weekly or monthly). A one-off bonus is added to your base earnings in the month it is paid. The calculator applies standard Class 1 NIC rates for the 2026/27 tax year: 8% on earnings between the Primary Threshold (£1,047.50 monthly / £12,570 annually) and the Upper Earnings Limit (£4,189.17 monthly / £50,270 annually), and 2% on all earnings exceeding the Upper Earnings Limit. Because NICs are calculated per pay period, a large bonus in a single month will typically cross the UEL, resulting in a 2% marginal NIC rate on the excess.
- Student Loan Repayments: If you have an active student loan (Plan 1, Plan 2, Plan 4, Plan 5, or Postgraduate), the calculator computes deductions on a non-cumulative basis. Repayments are calculated at 9% (or 6% for Postgraduate) on any earnings in the pay period that exceed the monthly equivalent of your plan's annual threshold. Since deductions are calculated weekly or monthly, a large bonus in a single month will trigger a high student loan deduction.
- Employer National Insurance and Pension Costs: The calculator also computes the employer's liability, including Employer Class 1 NICs (charged at the 2026/27 rate of 15% on earnings above the Secondary Threshold) and employer pension contributions (typically a minimum of 3% on qualifying earnings). If a salary sacrifice arrangement is in place, the calculator shows the employer's NIC savings, which some employers pass on to the employee's pension.
- Total Deductions Consolidation: The calculator aggregates the marginal Income Tax, Class 1 National Insurance, employee pension contributions, and student loan repayments attributable specifically to the bonus. It then subtracts this total from the gross bonus to determine your net take-home pay from the bonus and calculates your effective retention rate.
Real-World Examples
This scenario details the exact step-by-step mathematical calculations for an individual earning a base salary of £45,000 who receives a one-off £5,000 bonus. It assumes standard UK tax bands (England/NI/Wales), a standard 1257L tax code, no pension contributions, and no student loan repayments.
Step 1: Determine Base and Cumulative Earnings:
Base Annual Salary = £45,000.00
One-off Gross Bonus = £5,000.00
Total Combined Gross Earnings = £45,000.00 + £5,000.00 = £50,000.00
Step 2: Allocate Income Tax Bands (Higher Rate Threshold is £50,270):
Both base salary and total earnings fall below £50,270.
Therefore, the entire £5,000 bonus is taxed at the Basic Rate of 20%.
Income Tax on Bonus = £5,000.00 * 0.20 = £1,000.00
Step 3: Calculate Employee Class 1 National Insurance Contributions (NICs) on the Bonus:
NICs are calculated on a monthly pay-period basis.
Base Monthly Pay = £45,000.00 / 12 = £3,750.00
Monthly Pay with Bonus = £3,750.00 + £5,000.00 = £8,750.00
Monthly Upper Earnings Limit (UEL) = £4,189.17
- Portion of monthly pay below UEL: £4,189.17
- Base monthly pay already covers £3,750.00 of this.
- Portion of bonus taxed at standard Class 1 NIC rate (8%):
£4,189.17 - £3,750.00 = £439.17
NIC on this portion = £439.17 * 0.08 = £35.13
- Portion of bonus exceeding UEL taxed at the upper Class 1 NIC rate (2%):
£5,000.00 - £439.17 = £4,560.83
NIC on this portion = £4,560.83 * 0.02 = £91.22
- Total Class 1 NICs on Bonus = £35.13 + £91.22 = £126.35
Step 4: Sum Total Deductions on the Bonus:
Income Tax (£1,000.00) + National Insurance (£126.35) = £1,126.35
Step 5: Calculate Net Take-Home Pay from the Bonus:
Net Bonus Pay = £5,000.00 - £1,126.35 = £3,873.65
(This represents a net retention rate of 77.47% of the gross bonus.)This scenario illustrates the severe impact of the Personal Allowance taper. It details the step-by-step calculations for a £10,000 bonus on top of a £100,000 base salary, assuming standard UK tax bands (England/NI/Wales), a standard 1257L tax code, no pension contributions, and no student loan repayments.
Step 1: Determine Base and Cumulative Earnings:
Base Annual Salary = £100,000.00
One-off Gross Bonus = £10,000.00
Total Combined Gross Earnings = £100,000.00 + £10,000.00 = £110,000.00
Step 2: Calculate the Personal Allowance Taper:
For adjusted net income between £100,000 and £125,140, the Personal Allowance of £12,570 is reduced by £1 for every £2 of income.
Excess Income = £110,000.00 - £100,000.00 = £10,000.00
Reduction in Personal Allowance = £10,000.00 / 2 = £5,000.00
New Personal Allowance = £12,570.00 - £5,000.00 = £7,570.00
Step 3: Calculate the Income Tax on the Bonus:
- Because the Personal Allowance was reduced by £5,000.00, an extra £5,000.00 of income is pushed into the Higher Rate band (40%).
Additional Tax from Taper = £5,000.00 * 0.40 = £2,000.00
- The £10,000.00 bonus itself is taxed at the Higher Rate of 40%.
Standard Tax on Bonus = £10,000.00 * 0.40 = £4,000.00
- Total Income Tax on the Bonus = £2,000.00 + £4,000.00 = £6,000.00 (an effective 60% tax rate!)
Step 4: Calculate Employee Class 1 National Insurance Contributions (NICs) on the Bonus:
Base Monthly Pay = £100,000.00 / 12 = £8,333.33 (already exceeds UEL of £4,189.17)
Since the base monthly salary is already above the monthly UEL, the entire £10,000.00 bonus is taxed at the upper Class 1 NIC rate of 2%.
Class 1 NICs on Bonus = £10,000.00 * 0.02 = £200.00
Step 5: Sum Total Deductions on the Bonus:
Income Tax (£6,000.00) + National Insurance (£200.00) = £6,200.00
Step 6: Calculate Net Take-Home Pay from the Bonus:
Net Bonus Pay = £10,000.00 - £6,200.00 = £3,800.00
(This represents a net retention rate of only 38.00% of the gross bonus due to the 60% marginal tax trap.)Related Calculators
Frequently Asked Questions & Detailed Tax Guide
How are cash bonuses taxed in the UK?
There is a common misconception that cash bonuses are taxed at a special, higher rate in the UK. In reality, a bonus is treated as regular employment income by HMRC. It is subject to standard Income Tax rates (20%, 40%, or 45%) and employee National Insurance contributions (8% or 2%) at your highest marginal tax bracket. However, because payroll software calculates tax on each pay period in isolation, receiving a large bonus in a single month can temporarily push you into a higher tax bracket, resulting in a large upfront deduction.
What is “Bonus Sacrifice” and how does it save tax?
Bonus Sacrifice (or bonus exchange) is a scheme where you agree to swap some or all of your cash bonus in exchange for a direct, pre-tax contribution into your workplace pension. Because the money is paid directly into your pension before payroll runs, it avoids both Income Tax and employee National Insurance deductions entirely. This is one of the most effective tax-saving strategies for UK employees.
Step-by-Step Mathematical Calculation: Cash vs. Sacrifice
Let’s compare the net cash received from a £10,000 bonus for a higher-rate (40%) taxpayer:
Scenario A: Cash Bonus Paid in Payroll
- 1. Gross Bonus: £10,000.
- 2. Income Tax at 40%: £10,000 * 40% = £4,000.
- 3. National Insurance at 2%: £10,000 * 2% = £200.
- 4. Net Cash Received: £10,000 – £4,000 – £200 = £5,800 (42% total deduction).
Scenario B: Bonus Sacrifice into Pension
- 1. Salary sacrificed: £10,000.
- 2. Income Tax due: £0.
- 3. National Insurance due: £0.
- 4. Added to Pension Pot: £10,000 (saving £4,200 in tax and NI!).
- 5. Employer NI savings: The employer saves 13.8% NI (£1,380) on this bonus. Many employers pass back a portion of this saving (e.g. 50% or £690) to the employee’s pension pot, increasing the total pension addition to **£10,690**!
Tax Expert Pro-Tips: Tapering and Pension Allowances
David Vance, CTA FCA, recommends: “If your bonus pushes your annual income over £100,000, your personal allowance will taper, resulting in a 60% effective tax rate on that portion of the bonus. In this scenario, sacrificing the bonus into your pension is highly recommended, as it protects your personal allowance and reduces your tax liability. Always check that you have sufficient unused annual pension allowance (including carry forward) before executing a large bonus sacrifice.”
Legislative References
- Income Tax (Earnings and Pensions) Act 2003 – Valuation of employment income and bonuses.
- HMRC Employment Income Manual – Salary sacrifice and pension exchange rules.