Your gross salary is not the same as the amount that reaches your bank account. Income Tax, National Insurance and pension contributions all play a part. The way your pension is arranged can change the calculation even when the headline contribution looks identical.
Three common ways workplace pension contributions are handled
- Salary sacrifice: You agree to reduce contractual cash pay in exchange for an employer pension contribution. This can affect Income Tax and employee National Insurance, subject to scheme rules and current law.
- Net pay arrangement: Your pension contribution is deducted before Income Tax is calculated, but usually not before National Insurance is calculated.
- Relief at source: You contribute from pay after tax and the pension provider normally claims basic-rate tax relief. Some taxpayers may need to claim additional relief separately.
These arrangements are not interchangeable. A calculator that simply subtracts a percentage from salary without knowing the scheme type may produce the wrong take-home estimate.
Why your payslip might not match a calculator
Payroll calculations may use a different tax code, a different National Insurance category, bonuses, benefits, student loan deductions, irregular pay periods or Scottish Income Tax rates. Pension contributions may be based on qualifying earnings rather than the whole salary. Some employers also share part of their National Insurance saving, but this is not universal.
A useful comparison to run
First, calculate take-home pay without pension contributions. Next, add the contribution using the arrangement that matches your payslip or employer documents. Compare the change in take-home pay with the amount going into the pension. Do not assume the reduction in take-home pay will equal the pension contribution.
What salary sacrifice can affect beyond tax
Because contractual cash salary may be reduced, salary sacrifice can affect calculations linked to salary, such as some borrowing assessments or statutory benefits, depending on the rules and the employer's reference-salary policy. It is also subject to eligibility and minimum-wage restrictions. Check your scheme documents before making a change.
Important: UK tax and pension rules change. This guide explains the mechanics; it is not a recommendation to join, leave or change a pension scheme. For an actual payslip discrepancy, check your employer's payroll team or a suitably qualified professional.
Explore the figures using your own assumptions.
Open the take-home pay calculator →Life Figured provides general educational information and illustrative calculators, not personalised financial, tax or investment advice. Figures and assumptions may not reflect your circumstances.
