Why am I on an emergency tax code?

Almost always because HMRC is missing year-to-date information from a previous employer or tax period. Submitting a P45 or Starter Checklist resolves it within 1-2 pay cycles.

Does emergency code mean I'm paying more tax?

In most cases yes, temporarily. Non-cumulative calculation doesn't account for unused PA from earlier months, so you are usually over-taxed until the code goes cumulative. Any excess is refunded via subsequent payrolls or year-end reconciliation.

What is the emergency tax rate in the UK?

There is no separate emergency tax rate - the percentages are the standard 2026/27 Income Tax bands (20%, 40%, 45%). The reason emergency code costs more is that only 1/12th (M1) or 1/52nd (W1) of your £12,570 Personal Allowance is applied to each pay period, instead of the full year-to-date allowance. So in practice, mid-year starters often pay an effective 25-35% on that pay period vs the 12-18% they would owe under cumulative coding.

How much extra tax does emergency code take?

It depends on when in the tax year you start. The earlier in the year emergency code starts, the smaller the over-payment - because little PA has built up. By month 6 (October) the cumulative back-allowance is around £6,285, so a typical mid-year £35,000 starter on emergency M1 will be over-taxed by roughly £150-£250 per month until the code switches to cumulative.

What's the difference between W1, M1 and X?

W1 is weekly (used if paid weekly), M1 is monthly, and X is a generic non-cumulative marker that can apply to any frequency. Functionally they operate identically - taxing each pay period in isolation against 1/52 or 1/12 of the Personal Allowance.

How do I claim back overpaid emergency tax?

For employment income, you almost never need to claim - HMRC moves you to a cumulative code automatically once they have your year-to-date figures, and the next payroll refunds the over-paid tax. For pension flexible drawdown over-payments, file P55, P53Z or P50Z with HMRC - they refund within ~30 days rather than waiting until year-end. If you've stopped working partway through the year, file P50 to recover the unused PA.

Will I get a refund if emergency code over-taxed me?

Yes. Once HMRC converts you to a cumulative code (typically 1257L without the W1/M1/X suffix), the first cumulative payroll adjusts your year-to-date figures and refunds any over-paid tax through that payslip. If the tax year ends before that happens, HMRC's automatic year-end reconciliation issues a P800 calculation in the summer with refund instructions.

Is the old 50% emergency tax rule still in force?

No. There has not been a flat 50% emergency tax rate in modern PAYE - that figure is sometimes confused with the BR (Basic Rate, 20%) or 0T (no allowance, taxed at marginal rates from the first pound) codes used when HMRC has no information at all. The standard emergency code is 1257L W1/M1/X, which still gives you a slice of the PA each period.

Tax Code · 2026/27

Emergency Tax Code 2026/27: W1, M1 and X Suffixes

An 'emergency' tax code is a non-cumulative version of your main code. You'll see W1 (weekly), M1 (monthly), or X (either) appended - each pay period is taxed in isolation, which usually means you pay more tax than you owe.

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What the 1257L W1/M1/X tax code means

Under normal PAYE, your employer calculates tax using year-to-date pay and allowance totals - this 'cumulative' approach smooths out any under- or over-collection across the year.

An emergency code (W1, M1 or X suffix) switches to non-cumulative - each pay period is taxed in isolation, as if it were the first week or month of the tax year. You get 1/52nd or 1/12th of your Personal Allowance applied each period, with no year-to-date adjustment.

The code itself is usually 1257L W1 (weekly) or 1257L M1 (monthly). The W1/M1/X signal that HMRC hasn't yet received your full year-to-date information from a previous employer or pension.

There is no separate 'emergency tax rate' - the bands and percentages are exactly the same as the standard 2026/27 Income Tax (20% basic up to £50,270, 40% higher to £125,140, 45% above). What changes is that unused Personal Allowance from earlier in the tax year cannot offset later pay, so the tax taken in any single period can be much higher than the cumulative figure you actually owe by 5 April.

When you'll see 1257L W1/M1/X

You've just started a new job and haven't provided a P45 from your previous employer.
You completed a Starter Checklist but HMRC hasn't yet matched it to your full year record.
You had gaps in employment and HMRC is playing catch-up on year-to-date figures.
You moved from self-employment to employment mid-year.
You've taken a flexible drawdown lump sum from a pension - HMRC's first payment is almost always taxed on emergency M1, and the over-payment is reclaimed via P55, P53Z or P50Z.

What to do if you have a 1257L W1/M1/X code

Submit your P45 or Starter Checklist to your new employer at the earliest opportunity - this is the fastest path to a full cumulative code.
Check your Personal Tax Account on gov.uk to see the code HMRC has on file and the reason for non-cumulative handling.
Once HMRC has the full year-to-date, they'll remove the suffix and issue a standard 1257L code. Any over- or under-tax from the emergency period is reconciled through the next payroll - you do not need to file self-assessment for this alone.
If emergency coding lasts more than 2 months, contact HMRC on 0300 200 3300 - they can manually push the full code to your employer.
For pension flexible drawdown over-payments, file form P55 (more pension to take), P53Z (pension fully drawn, still working) or P50Z (pension fully drawn, not working) - HMRC repays within 30 days rather than waiting for year-end reconciliation.

Worked example

You start a new job on 1 June paying £35,000/year (£2,917/month) with no P45 submitted. Your employer applies 1257L M1. In June, only 1/12th of the PA (£1,047.50) is set against your £2,917 pay, leaving £1,869.50 taxable at 20% - that is £374 income tax for the month. Under cumulative 1257L, your April-May allowance carries forward, so June tax would only be roughly £140 (you would have effectively had £4,190 of PA still untouched). The £234 monthly over-tax keeps coming until HMRC switches you to cumulative; the first cumulative payroll then refunds the running total in one payslip.

Want to see the numbers for your own salary? Use the salary calculator and pick 2026/27 to see how 1257L W1/M1/X interacts with your full take-home.

Frequently asked questions about 1257L W1/M1/X

Why am I on an emergency tax code?: Almost always because HMRC is missing year-to-date information from a previous employer or tax period. Submitting a P45 or Starter Checklist resolves it within 1-2 pay cycles.
Does emergency code mean I'm paying more tax?: In most cases yes, temporarily. Non-cumulative calculation doesn't account for unused PA from earlier months, so you are usually over-taxed until the code goes cumulative. Any excess is refunded via subsequent payrolls or year-end reconciliation.
What is the emergency tax rate in the UK?: There is no separate emergency tax rate - the percentages are the standard 2026/27 Income Tax bands (20%, 40%, 45%). The reason emergency code costs more is that only 1/12th (M1) or 1/52nd (W1) of your £12,570 Personal Allowance is applied to each pay period, instead of the full year-to-date allowance. So in practice, mid-year starters often pay an effective 25-35% on that pay period vs the 12-18% they would owe under cumulative coding.
How much extra tax does emergency code take?: It depends on when in the tax year you start. The earlier in the year emergency code starts, the smaller the over-payment - because little PA has built up. By month 6 (October) the cumulative back-allowance is around £6,285, so a typical mid-year £35,000 starter on emergency M1 will be over-taxed by roughly £150-£250 per month until the code switches to cumulative.
What's the difference between W1, M1 and X?: W1 is weekly (used if paid weekly), M1 is monthly, and X is a generic non-cumulative marker that can apply to any frequency. Functionally they operate identically - taxing each pay period in isolation against 1/52 or 1/12 of the Personal Allowance.
How do I claim back overpaid emergency tax?: For employment income, you almost never need to claim - HMRC moves you to a cumulative code automatically once they have your year-to-date figures, and the next payroll refunds the over-paid tax. For pension flexible drawdown over-payments, file P55, P53Z or P50Z with HMRC - they refund within ~30 days rather than waiting until year-end. If you've stopped working partway through the year, file P50 to recover the unused PA.
Will I get a refund if emergency code over-taxed me?: Yes. Once HMRC converts you to a cumulative code (typically 1257L without the W1/M1/X suffix), the first cumulative payroll adjusts your year-to-date figures and refunds any over-paid tax through that payslip. If the tax year ends before that happens, HMRC's automatic year-end reconciliation issues a P800 calculation in the summer with refund instructions.
Is the old 50% emergency tax rule still in force?: No. There has not been a flat 50% emergency tax rate in modern PAYE - that figure is sometimes confused with the BR (Basic Rate, 20%) or 0T (no allowance, taxed at marginal rates from the first pound) codes used when HMRC has no information at all. The standard emergency code is 1257L W1/M1/X, which still gives you a slice of the PA each period.

All UK tax codes →

Sources & further reading

All figures and definitions on this page reflect the 2026/27 UK tax year and are cross-checked against HMRC guidance.

HMRC — What your tax code means (official meanings for L, BR, D0, D1, K, 0T, NT, M, N, S, C, T)
HMRC — Income Tax rates and Personal Allowance (2026/27 bands and thresholds)
HMRC — Emergency tax codes (W1, M1 and X suffixes)
HMRC — Rates and thresholds for employers 2026 to 2027
HMRC — Your Personal Tax Account (check your current code and how it was calculated)
Our methodology & calculation sources →