If your payslip shows a different amount, start with the tax year, gross pay and deduction settings. Then check these common reasons.
Checked . Based on official GOV.UK guidance. About our calculators and content.
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Your tax code and earlier pay
Payroll may use the pay and tax from earlier in the year. An emergency code or an adjustment for benefits or unpaid tax can also change the result. The calculator does not read your previous payslips.
NI and student loans
Your employer calculates these deductions for each pay period. A bonus or uneven shifts can give a different result from an annual estimate divided by twelve. Historical NI estimates also average changes within a tax year.
Your pension scheme
Check whether your pension uses net pay, relief at source or salary sacrifice. Then check whether the percentage applies to full or qualifying earnings, and whether bonuses and overtime count. Other payroll deductions and rounding may explain the rest.
Source: Read the original rules and guidance. Content checked 23 October 2026. General explanation, not personalised tax advice.