Keep the two payslip lines in separate columns
| Question | PAYE income tax | Employee National Insurance |
|---|---|---|
| Primary driver to verify | The employee tax code and taxable-pay records | The NI category, pay frequency and NI earnings |
| First record to inspect | HMRC tax-code service and payslip | Payslip category and payroll period |
| Wage101 coverage | No official PAYE calculator | Category A weekly or monthly estimate only |
| What a matching line does not prove | Final annual liability or refund | Correct category, adjustments or every NI case |
Review the source record before the arithmetic
- Match the payslip to the correct pay period and gross-pay records.
- Compare the payslip tax code with the current HMRC record.
- Confirm the NI category letter instead of inferring it from age or job title.
- Use weekly pay with weekly NI thresholds or monthly pay with monthly thresholds.
- Take unexplained adjustments, refunds or prior-period corrections to payroll or HMRC.
Frequently asked questions
- Do PAYE and National Insurance always use the same pay base?
- Do not assume so. Verify taxable pay and NI earnings from the applicable payroll records and official guidance; this article does not reconstruct either base.
- Why does the Wage101 calculator ask for Category A confirmation?
- Because the implemented engine contains only the reviewed Category A branch. Choosing another category or inferring the category would exceed its evidence and calculation scope.
Sources checked
- Check if the tax on your payslip is correct — HM Revenue & Customs (accessed 2026-08-01): PAYE, tax-code, gross-pay, deduction and net-pay interpretation only.
- Payslips: employee rights — UK Government (accessed 2026-08-01): Great Britain payslip coverage and required-field context; Northern Ireland is checked separately.