Why is my pay different this month?

Paste the figures from your previous payslip into the left column and the current one into the right. We'll compute the line-by-line delta, tell you which movements drove the change, and surface the common UK causes — a pay rise, a bonus month, a tax code change, a benefit-in-kind, a student loan threshold crossed. Everything stays in your browser.

Deductions

Current payslip

Deductions

All figures stay in your browser. We never transmit or store any payslip amounts; analytics records which lines moved, not how much.

How to use this tool well

  1. Use the two most recent payslips from the same employer. Comparing payslips from different employers isn't meaningful because the tax code and NI category can be different.
  2. Match the period type. If one is a 4-weekly and the other is monthly, differences will mostly be from the period length, not from pay or policy changes.
  3. Check the tax code field on both. A tax code change (e.g. 1257L → 1137L, or a new W1/M1 marker) is the single most common reason PAYE moves.
  4. Add anything shown on the payslip to "Other deductions" — season ticket loan, union subs, give-as-you-earn, court order, overpayment recovery. These stay the same month-to-month only if nothing changed with them.

Related tools and guides

Methodology

Expected figures use the 2026/27 UK tax year and the published HMRC bands. The comparison narrative uses deterministic rules documented in our methodology page. We flag line movements of £1 or more as material changes worth discussing.

This tool does not store or transmit any payslip values. Analytics records only non-sensitive categorical event metadata (which line moved, which explanation card was opened); it never records monetary amounts, tax codes, or any personal data.

Last reviewed October 2026. Sources: GOV.UK Income Tax rates, GOV.UK tax codes, GOV.UK payslips.

Not financial advice. If a change persists and you can't explain it from the possibilities we list, speak to your payroll department — they are required to walk you through their calculation on request.