Emergency Tax Codes UK (2026/27) — W1, M1 & X Codes Explained
Emergency tax codes ending in W1 (Week 1), M1 (Month 1), or X calculate your PAYE Income Tax on a non-cumulative basis. Instead of looking at your total earnings and tax paid since 6 April, your payroll software calculates tax on that single pay period in isolation—allocating exactly £1,047.50/month (£241.73/week) of tax-free pay on 1257L W1/M1.
| Emergency Tax Code | Monthly Tax-Free Allowance | How Payroll Calculates Deductions |
|---|---|---|
| 1257L W1 / 1257L M1 / 1257L X | £1,047.50 / month (£241.73/wk) | Non-cumulative: each pay packet taxed in isolation |
| 0T W1 / 0T M1 | £0.00 / month | Zero allowance; progressive bands per isolated period |
| BR W1 / BR M1 | £0.00 / month | Flat 20% Basic Rate deducted from every pound |