UK tax code and emergency tax checker 2026/27
Decode common PAYE tax codes, identify emergency markers and estimate the annual tax treatment the code suggests.
How the Tax code checker estimate works
The checker decodes common allowance, flat-rate, zero-allowance and K codes, recognises emergency markers and gives a deliberately limited annual projection. Payroll history is not available to the tool.
Rules checked
Read the checking method
What the result includes
- Scottish and Welsh prefixes where relevant
- W1, M1, X and NONCUM emergency markers
- The 50%-of-pay collection ceiling for a K-code projection
What to have ready
- The exact code from a current payslip or HMRC notice
- Gross annual pay from that employment
- Year-to-date pay and tax for a separate payroll reconciliation
Questions about Tax code checker
Is a tax code a final tax calculation?
No. It is an instruction used by payroll. The final liability depends on actual annual income, allowances and tax already paid.
What does a W1 or M1 marker change?
Payroll calculates the current week or month without looking back across the tax year, which can delay use of allowances or collection of tax.
About this estimate
A code is an instruction to payroll, not a final tax calculation. Benefits, earlier pay, multiple jobs and week 1 or month 1 treatment can materially change deductions.