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# Emergency Tax Code: What W1, M1 and X Mean and How to Fix It
- URL: https://www.kaeltripton.com/what-is-the-emergency-tax-code/
- Published: 2026-05-14T22:20:19.000Z
- Updated: 2026-11-10T20:10:56.000Z
- Description: An emergency tax code ends in W1, M1 or X, so each pay period is taxed on its own. HMRC usually corrects the code within 35 days of starting a job.
- Author: Chandraketu Tripathi
- Tags: Tax & HMRC, uk-finance, money-guides

TAX

An emergency tax code ends in W1, M1 or X, for example 1257L M1\. Each pay period is taxed on its own instead of on total pay since 6 April. It is common in a new job without a P45, and HMRC usually corrects it within 35 days.

Last reviewed 10 November 2026

**Key facts**
- Emergency codes end in W1 (weekly pay), M1 (monthly pay) or X (pay dates vary)
- NONCUM on a payslip means the same thing on some payroll systems
- HMRC usually updates the code within 35 days of starting a job
- Overpaid tax can be refunded; underpaid tax keeps the emergency basis until the right tax is paid
- Starting a company benefit or State Pension can trigger an emergency code until the tax year ends
- Personal Allowance 2026/27: £12,570, so the usual emergency code is 1257L W1 or 1257L M1

## What makes a tax code an emergency code

**An emergency tax code is a non-cumulative code. It ends in W1 for weekly pay, M1 for monthly pay or X when pay dates vary. Some payroll systems show NONCUM instead. Tax is worked out only on that week's or month's pay, as if that amount were paid every period of the year.**

The suffix is the key signal. W1 means weekly pay, M1 means monthly pay and X means pay dates vary. NONCUM means non-cumulative, the same basis as W1, M1 or X, shown that way by some payroll software. A code such as [tax code 1257L](https://www.kaeltripton.com/what-is-tax-code-1257l/) with W1 or M1 added is therefore on an emergency basis, even though the number itself looks like the usual code.

On a cumulative code, payroll uses total pay and tax since 6 April to work out the position in each pay period. On an emergency code, each pay period is taxed on its own instead of on total pay since 6 April. This ignores pay and tax earlier in the tax year, so the tax taken can be too high or too low. The effect appears in [payslip deductions](https://www.kaeltripton.com/uk-payslip-deductions-master-guide/) as more or less income tax than a cumulative code would give.

Personal Allowance for 2026/27 is £12,570, so the usual emergency code is 1257L W1 or 1257L M1\. The W1 or M1 suffix does not change the Personal Allowance figure. It changes how that allowance is applied across the year. A weekly paid employee gets one week's share of the allowance each week. A monthly paid employee gets one month's share each month. With X, pay dates vary, so the emergency basis is used where a fixed weekly or monthly pattern does not apply.

NONCUM on a payslip should be read in the same way as W1, M1 or X. The suffix and the label are two ways of showing the non-cumulative basis. That reading helps separate an emergency basis from a cumulative code.

## Why you are on an emergency code

**An emergency code can start when a new job begins without a P45 or without the starter checklist information. It can also start with a company benefit such as a car or medical cover, with the State Pension, or when HMRC does not yet have income details from a previous job.**

A new job without a [P45](https://www.kaeltripton.com/uk-p45-p60-p11d-explained/) is a common cause. Without it, payroll may not have the information needed for a cumulative code, so an emergency code is used until HMRC provides one. The same can happen when the starter checklist information is incomplete or not given to the new employer.

A company benefit can also trigger an emergency code. A car or medical cover starting during the tax year can change the tax position. The emergency code can apply until the tax year ends, with a normal code from the next tax year. The State Pension starting can have a similar effect. HMRC may not yet have income details from a previous job, which can also lead to an emergency code.

An emergency code is not the same as every other code. Other codes can have different causes, including [tax code 0T M1](https://www.kaeltripton.com/tax-code-0t-m1/). The suffix and the number both matter. W1, M1 or X points to the emergency basis. NONCUM on a payslip means the same thing. A code without those suffixes may still be wrong, but the reason is different. Checking the code letters and numbers helps separate an emergency code from another issue.

Guidance on [emergency tax on pension withdrawals](https://www.kaeltripton.com/uk-emergency-tax-on-pension-withdrawal/) covers a separate area. For this page, the focus is the emergency code from a job, a company benefit or the State Pension.

The starter checklist is the alternative when a P45 is not available. Without the checklist information, an emergency code can remain until HMRC issues a new code.

## Worked example: starting a job in October on 1257L M1

**Someone earning £2,500 a month who starts in October with no P45 and code 1257L M1 is taxed on each month alone. One twelfth of the allowance is £1,047.50, so £1,452.50 is taxed at 20%, which is £290.50 a month.**

On M1, each month gets one twelfth of the allowance: £1,047.50\. The pay of £2,500 less that allowance leaves £1,452.50 taxed at 20%, so £290.50 a month. That figure is the same each month under M1, whatever pay and tax came earlier in the tax year.

On a cumulative code, unused allowance from April to September would also be given. The first month in October could therefore use allowance from earlier months, so less tax or none would be due in that first month. The exact result depends on pay and tax earlier in the tax year, but the direction is clear: M1 does not give the earlier unused allowance.

Once the cumulative code is applied, payroll refunds the overpayment through pay. The refund happens because the cumulative code recalculates the tax due on total pay since 6 April and compares it with tax already taken. The emergency code charged £290.50 a month on the M1 basis. A cumulative code can give a different figure and the difference is returned through payroll.

The example uses the usual emergency code for 2026/27, 1257L M1, based on the £12,570 Personal Allowance. The M1 suffix means monthly pay. For weekly pay the suffix would be W1\. For pay dates that vary, the suffix would be X. The number 1257L supplies one twelfth of the allowance each month under M1\. The suffix supplies the non-cumulative basis.

The same arithmetic applies with W1 for weekly pay. One week's share of the allowance is used each week. The X suffix is used where pay dates vary, so the fixed weekly or monthly share does not apply. The principle is the same: the emergency basis does not use earlier pay and tax in the tax year.

## How long an emergency code lasts

**An emergency code is usually temporary. HMRC normally issues a new code within 35 days of starting a job. If the code still looks wrong after 35 days, update details with HMRC. For a company benefit or State Pension, the emergency code can run to the end of the tax year.**

The usual pattern is short. HMRC normally issues a new code within 35 days of starting a job. A cumulative code lets payroll recalculate the tax position from 6 April. The employer applies the new code from the next pay period after it is received. The first payslip on the new code may show a refund if the emergency code took too much tax.

If the code still looks wrong after 35 days, update details with HMRC. The update can be made in the HMRC app or personal tax account. HMRC issues the new code to the employer. A call or online update can prompt a new code. The new code then goes to payroll.

For a company benefit or State Pension, the emergency code can run to the end of the tax year, with a normal code from the next tax year. That is different from the 35 day pattern for a new job. The benefit or State Pension changes the tax position for the rest of the year, so the emergency basis can stay in place until the year ends. A normal code follows from the next tax year.

The code can also change after HMRC receives information from a previous employer. A new job may start before that information arrives, so the emergency code is used in the meantime. Once the details are updated, HMRC can issue a cumulative code. The employer then applies it from the next pay period. The 35 day period is a usual guide, not a fixed rule for every case.

## How to get off an emergency code and claim back tax

**Give the new employer the P45 parts 2 and 3\. Without a P45, complete the starter checklist. Check and update income details in the HMRC app or personal tax account. Overpaid tax is usually returned through payroll. If not, HMRC can repay after the tax year ends.**

Giving the new employer the P45 parts 2 and 3 is the first step. That normally lets payroll use the right cumulative code from the start, which avoids or shortens emergency tax. If the P45 was not sent, ask the old employer for it. Without a P45, complete the starter checklist. The checklist gives the new employer the information needed to set a code.

Check and update income details in the HMRC app or personal tax account. The update should cover the new job and any previous job. HMRC can then issue a new code to the employer. The employer applies the new code from the next pay period after it is received.

Overpaid tax is usually returned through payroll. If not, HMRC can repay after the tax year ends. The [HMRC tax rebate](https://www.kaeltripton.com/hmrc-tax-rebate-uk-2026-guide/) guidance covers repayment claims. A claim after the tax year ends can use the final pay and tax figures. The emergency code may have taken too much tax during the year, and the repayment returns the difference.

For a company benefit or State Pension, the code can run to the end of the tax year. The step is still to check the details with HMRC. A normal code from the next tax year then replaces the emergency code. The payroll refund or HMRC repayment follows the same principle.

The starter checklist is the step when a P45 is not available. The information goes to the new employer for the code. The HMRC app or personal tax account can then be used to check the details. A new code goes to the employer after the update.

**Related terms**
- [Tax code 1257L](https://www.kaeltripton.com/what-is-tax-code-1257l/)
- [Tax code 0T M1](https://www.kaeltripton.com/tax-code-0t-m1/)
- [Reclaim overpaid tax with a P50](https://www.kaeltripton.com/reclaim-overpaid-tax-after-redundancy-p50-uk/)
- [Emergency tax on pension withdrawals](https://www.kaeltripton.com/uk-emergency-tax-on-pension-withdrawal/)
- [UK money glossary](https://www.kaeltripton.com/glossary/)

**Disclaimer:** This page is general information about UK rules, not personal tax or financial advice. Figures apply to the 2026/27 tax year unless stated. Check your own position with HMRC.

## Frequently asked questions

### What is the emergency tax code for 2026/27?

It is usually 1257L W1 for weekly pay or 1257L M1 for monthly pay, based on the £12,570 Personal Allowance. An X suffix is used when pay dates vary. The number reflects the allowance.

### How long does emergency tax last?

HMRC usually updates the code within 35 days of starting a job. For a new company benefit or State Pension it can last until the end of the tax year.

### Is emergency tax refunded?

Overpaid tax is normally refunded through payroll once a cumulative code is in place. If not, HMRC can repay after the tax year ends. The refund returns the difference between the emergency basis and the cumulative basis.

### Does a P45 stop emergency tax?

Giving the new employer the P45 usually lets them use the right cumulative code from the start, which avoids or shortens emergency tax. The P45 parts 2 and 3 are the parts to give.

### Is NONCUM the same as an emergency code?

Yes. NONCUM means non-cumulative, the same basis as W1, M1 or X, shown that way by some payroll software. The label appears on the payslip, while W1, M1 or X appears in the code.

## Sources

- [HMRC via GOV.UK: Emergency tax codes](https://www.gov.uk/tax-codes/emergency-tax-codes?ref=kaeltripton.com)
- [HMRC via GOV.UK: What your tax code means](https://www.gov.uk/tax-codes/what-your-tax-code-means?ref=kaeltripton.com)
- [GOV.UK: P45, P60 and P11D forms](https://www.gov.uk/paye-forms-p45-p60-p11d?ref=kaeltripton.com)