Quick answer
Most employment bonuses are subject to income tax, employee National Insurance and possibly student loan repayments.
A large one-off bonus can push that month or week into a higher apparent deduction, even if the final annual tax position is adjusted across the tax year.
Worked example: £3,000 bonus on top of salary
If you receive a £3,000 annual bonus, payroll normally adds it to taxable pay in the period it is paid.
For a monthly-paid employee, that month may show higher income tax, employee NI and student loan repayment than a normal month.
The annual salary calculator can model a simple annual bonus by adding the bonus to yearly gross pay, but it does not reproduce every employer's month-by-month PAYE calculation.
Why bonus deductions can feel high
PAYE uses payroll period calculations. A one-off bonus can make one month's taxable pay look unusually high, which can affect tax and loan deductions in that month.
Employee National Insurance is also calculated by pay period for most employees. That means the timing of a bonus can matter.
Pension treatment depends on employer rules. Some schemes include bonuses in pensionable pay and others do not.
Common mistakes
Assuming the bonus will be taxed at one flat rate. It is usually added to payroll income and taxed through PAYE bands and period rules.
Forgetting student loan repayments. A bonus can increase repayment in the period it is paid if earnings are above the relevant threshold.
Comparing a bonus month with a normal month without allowing for year-to-date payroll adjustments.
Try the calculator
Use the related calculator to test the numbers against your own assumptions.
UK Salary CalculatorDisclaimer
This guide is for planning only. Bonus payroll can differ by tax code, employer setup, pension rules, pay frequency and year-to-date position.