An emergency tax code is a tax code applied on a non-cumulative basis. Your tax is worked out on each payment on its own, as if you earned that amount every week or month of the year, ignoring what you have earned and paid earlier in the tax year. For 2026/27 HMRC lists the emergency codes as 1257L W1 (weekly pay), 1257L M1 (monthly pay) and 1257L X. Each gives the standard £12,570 Personal Allowance, but only one week's (£242) or one month's (£1,048) share of it at a time.
How to tell if you are on an emergency tax code
Look at the end of the code on your payslip. HMRC's guidance says you are on an emergency code if it ends in:
- W1. Used when you are paid weekly, for example 1257L W1;
- M1. Used when you are paid monthly, for example 1257L M1;
- X. Used when pay dates vary;
- NONCUM. Some payroll software shows "NONCUM" (non-cumulative) instead.
If the code does not end in W1, M1, X or NONCUM, it is not an emergency code. A plain 1257L is the normal cumulative code. Codes such as 0T and BR are different again, and can themselves be operated on a week 1/month 1 basis.
What an emergency tax code means for your pay
Normally PAYE is cumulative. Each payday, payroll compares your total pay since 6 April with your total tax-free allowance to date, and over- or under-deductions correct themselves. On an emergency code that look-back is switched off. Each pay period stands alone, with one period's worth of allowance and one period's worth of each tax band.
The effect depends on your history in the tax year:
- You had no income earlier in the year. You will usually overpay, because the allowance you did not use in earlier months is not given to you;
- You already used your allowance in a previous job. You may underpay, because the emergency code gives you allowance a second time.
Illustration (not an HMRC example). Someone with no income since 6 April starts a job in October on £3,000 a month and is put on 1257L M1. Payroll gives £1,048 tax-free and taxes the remaining £1,952 at 20%, which is £390.40. On a cumulative 1257L code in the seventh tax month, the allowance to date would be seven-twelfths of £12,570, or £7,332.50. That covers the £3,000 earned, so no tax would be deducted that month. The extra tax is not lost. It comes back once the correct cumulative code is issued, or after the year end.
Why you have been put on an emergency code
Starting a new job without a P45. This is the usual reason. The starter checklist asks new employees to choose a statement:
- Statement A. This is my first job since 6 April, with no taxable JSA, ESA or Incapacity Benefit and no state or occupational pension. HMRC's manual says the employer uses the emergency code on a cumulative basis, which in practice is a plain 1257L without W1 or M1;
- Statement B. This is now my only job, but since 6 April I have had another job or received those benefits, and I do not get a state or occupational pension. The employer uses the emergency code on a week 1/month 1 basis;
- Statement C. I have another job or a pension. The employer uses code BR;
- No statement chosen. HMRC's PAYE Manual sets 0T on a week 1/month 1 basis.
Starting company benefits or the State Pension. HMRC may put you on an emergency code mid-year so the extra tax is collected in the current year. Gov.uk says this "is normal", and you stay on it until the tax year ends.
No code notice received. HMRC's manual also lists employees for whom the employer has received no code notice, and some late P45 cases.
How long it lasts and how to get off it
HMRC usually issues a corrected code once it has details from both your new and previous employers. This can take up to 35 days from when you start. The new code goes to you and your employer. Once the employer applies a cumulative code, any overpaid tax is normally refunded through payroll. Monthly-paid staff should see the new code on their next or following payslip, and weekly-paid staff by their third.
To speed things up:
- Give your new employer your P45. If your old employer did not issue one, ask for it. If the P45 is given after your first payday, the employer uses the code HMRC has sent, or the P45 code if HMRC has not sent one yet;
- Complete the starter checklist accurately. Ticking the wrong statement is a common cause of a week 1/month 1 code;
- Check your details online. After 35 days, if the code is still wrong, use HMRC's Check your Income Tax service or the HMRC app to update your employment and income details.
If an emergency code has left you underpaid, HMRC normally adjusts a later code or sends a P800 calculation after the tax year. Where the underpayment arose because HMRC itself failed to act on information it held, the concession for HMRC errors may apply. Our wrong tax code guide covers that.
Emergency code, 0T and BR compared
| Code | Allowance given | Typical use |
|---|---|---|
| 1257L W1/M1/X | Standard allowance, one period at a time | New starter without P45 (Statement B); mid-year changes |
| 0T (often W1/M1) | None | No starter information; allowance used up |
| BR | None; all pay at basic rate | Second job or pension (Statement C) |
For the 0T code specifically, see our 0T tax code guide. HMRC's own explanations are on its emergency tax codes page and in the PAYE Manual on starter statements.
Acumon's PAYE services team sets starter codes correctly from the outset. Our income tax returns service handles reclaims where an emergency code has caused overpaid tax across more than one job. Employers can avoid most emergency codes by collecting the P45 or starter checklist before the first payroll run.