1. Annualise the pay
The calculator starts by converting the amount entered into an annual figure. Monthly pay is multiplied by 12, weekly pay by 52, and daily pay by 260. Annual bonus is then added to create the annual gross pay used in the rest of the model.
2. Apply salary sacrifice pension
The salary sacrifice pension percentage is applied to annual gross pay, including bonus. That sacrificed amount is treated as leaving pay before Income Tax, employee National Insurance, employer National Insurance, and loan calculations are estimated.
3. Work out Income Tax
The calculator uses 2026/27 band assumptions for either Scotland or the rest of the UK. It also models the standard tapering of the personal allowance above £100,000 so users can see the impact in higher earning ranges.
4. Work out employee and employer NI
Employee NI uses annual Class 1 Category A thresholds and rates in this simplified model. Employer NI is also shown so users can compare their salary with the broader cost to an employer. Selecting State Pension age removes employee NI from the estimate.
5. Work out loans
UK Net Pay supports student loan plans 1, 2, 4, and 5, plus an optional postgraduate loan. Thresholds are handled annually and repayments are shown separately from tax and NI so users can see why take-home pay changes.
6. Show average pay periods
After annual deductions are calculated, the site divides them into year, month, week, and day averages. This is especially useful for comparing jobs or seeing the planning impact of a pay rise.
What is not included
- Custom tax codes and cumulative payroll history
- Marriage allowance, blind person allowance, or child benefit charge
- Dividends, savings income, self-employment, or company benefits
- One-off payroll handling for irregular bonus months