Emergency Tax Code UK 2026/27 — W1, M1 and X Explained

An emergency tax code is a temporary PAYE code used when HM Revenue and Customs (HMRC), an employer or a pension provider does not yet have enough reliable information to operate a normal cumulative code. It does not create a special rate of Income Tax. Instead, it changes how the payroll calculation uses your allowance and tax bands for the current pay period.

For the 2026/27 tax year, the standard emergency allowance code is generally 1257L when it is used with an emergency basis. You can identify the emergency basis from the suffix: W1 for weekly pay, M1 for monthly pay or X where pay dates vary. You may also see NONCUM on a payslip, depending on the payroll software. The code could therefore appear as 1257L W1, 1257L M1 or 1257L X.

The practical effect is that PAYE is calculated from the current week or month rather than using your total pay and tax so far in the tax year. If you have already earned money or paid tax elsewhere, the calculation may temporarily be wrong. That can mean too much tax is deducted, although the final outcome depends on your complete circumstances and the code HMRC instructs the employer to use.

How do I recognise an emergency tax code?

HMRC says you are on an emergency tax code if your code ends in W1, M1 or X. W1 means the payroll calculation is based on the first week of the tax year for that job. M1 means the first month. X is used when the pay dates vary. The visible code may include a prefix, such as S or C, where the tax treatment reflects Scotland or Wales, so read the complete code rather than looking only at the number.

The number before the letter is the allowance element. For 2026/27, HMRC's P9X guidance says the emergency code is 1257L for all employees and that the PAYE starting point is £242 per week or £1,048 per month. Those figures describe the standard 2026/27 payroll code and thresholds; they do not mean every person is entitled to use 1257L. HMRC may reduce or replace the allowance where it has information about another job, pension, taxable benefits, unpaid tax or a relief claim.

Do not assume that every code containing 1257L is an emergency code. HMRC explains that 1257L is the common code for many people with one job and no untaxed income, unpaid tax or taxable benefits. It becomes an emergency code when it is followed by W1, M1 or X. A normal cumulative 1257L uses the tax and pay information built up through the year, whereas 1257L M1 ignores earlier pay and tax for the relevant calculation.

Why might a new job use an emergency code?

The most common situation is starting a new job before the employer has your previous employment details. Your previous employer should normally give you a P45 when you leave. The P45 contains pay and tax information needed for the new payroll. If it is unavailable, delayed or not passed to the new employer, the new payroll may use an emergency code until HMRC receives enough information.

You may also need to complete the starter checklist if you do not have a P45 or your new employer needs more information. HMRC's checklist asks about your employment circumstances and helps the employer work out the first code, tax deduction and, where relevant, student or postgraduate loan deductions. Answer the checklist based on your actual circumstances. Selecting the wrong statement can produce a code that appears plausible but does not reflect whether this is your first job, an additional job or a job after another source of income.

An emergency code is not evidence that your employer has done something improper. It is a provisional payroll solution while the records are brought together. However, you should still check your first payslip and make sure the employer has your correct name, address, National Insurance number, leaving date and P45 information. A payroll system cannot correct missing information that it has never received.

What should I do when I receive a P45?

Give the P45 to your new employer promptly and keep a copy or a clear record of the information. The employer uses it to update the payroll record and report the new employment. Do not send a P45 from a current job to another employer if the document does not relate to the employment you have left; ask the payroll or HR team what information they need instead.

Once HMRC has the information from the new and previous employers, HMRC will usually update the tax code and send it to both you and the employer. HMRC's emergency-code guidance says this can take up to 35 days from the date you start the job. That is a process estimate, not a promise that every payroll correction will appear in the next payslip. The employer also needs time to receive the notice and run payroll.

If more than 35 days have passed and the code still appears wrong, use HMRC's online service to check and update your Income Tax details. Review the employment start date, previous pay, tax already deducted, estimated annual pay and any benefits. If the online record is correct but payroll is still using the old code, contact the employer's payroll team and ask them to check for the latest HMRC coding notice.

Why does an emergency code calculate tax differently?

Most PAYE codes are operated cumulatively. A cumulative calculation considers pay and tax from the start of the tax year, including earlier pay reported under the same employment record. It can adjust the deduction up or down as your pay changes. An emergency W1, M1 or X basis instead treats the current pay period as if it were the first relevant period, so it does not use the earlier pay and tax that a cumulative calculation would use.

This difference matters when you move jobs. Suppose you earned pay from one employer earlier in the tax year and then start another job. A cumulative code can use the P45 information to account for the earlier pay and tax. An emergency M1 code cannot make that adjustment until the missing information is available. The first payslip may therefore show a deduction that is higher or lower than the eventual amount for the whole tax year.

An emergency code also does not necessarily mean that you are taxed at the wrong percentage on every pound. The issue is often the timing and the information used by the calculation. Your tax code may include the standard allowance, but the non-cumulative basis can produce a different result from the same number on a cumulative basis. Compare the complete code, the pay frequency and the taxable pay rather than comparing only the tax amount with a monthly estimate.

Can company benefits or State Pension cause an emergency code?

HMRC says an emergency code can be used when you start receiving company benefits or the State Pension. In that situation, the code may help collect the right tax during the year while HMRC adds the new taxable income to the record. This can be normal, but you should check that the code includes the correct benefit or pension information.

Company benefits such as a taxable car, medical insurance or accommodation can change the code even though they are not paid as cash in your payslip. If HMRC has the wrong benefit value, wrong start date or a benefit that has stopped, the code can remain unsuitable. Review the benefit details in the HMRC online service and tell HMRC when the facts change. Do not remove a genuine taxable benefit merely because it reduces your monthly cash pay.

The State Pension is also taxable income, although tax is usually collected through another pension or employment rather than deducted directly from the State Pension payment. If you start receiving it, check which pension or job HMRC has selected for the code and whether the estimated annual amount is accurate. A code change can be appropriate without meaning that you have been placed on a penalty rate.

What if too much tax has been deducted?

If the emergency code is corrected during the tax year, the employer or pension provider can normally adjust later PAYE deductions using the updated code. A cumulative code can take earlier pay and tax into account and may produce a refund through payroll, depending on the figures. The correction is not necessarily a separate cash payment from HMRC.

If the tax year has ended, HMRC may reconcile the year and issue a tax calculation or refund where the records show that too much tax was paid. Keep payslips, the P45, P60, coding notices and evidence of the dates on which you supplied information. These documents help distinguish an emergency-code overpayment from an amount caused by an incorrect estimate, an additional job, taxable benefits or another tax liability.

Do not stop PAYE deductions yourself or ask the employer to ignore an HMRC code because the tax amount looks high. The employer is required to operate the code HMRC supplies. If the code is wrong, correct the underlying information through HMRC and payroll. If you are due a refund, the route and timing depend on whether the correction happens during the tax year or through an end-of-year reconciliation.

What if too little tax has been deducted?

An emergency code can also lead to too little tax being deducted in some circumstances. HMRC may keep an emergency code in place until the correct cumulative position is known. If the final calculation shows an underpayment, HMRC can change a future code or collect the amount through another process. Do not assume that an emergency code always means a refund.

Check all jobs and pensions shown in your HMRC account, not just the employer that issued the latest payslip. An additional job may have a BR, 0T or another code rather than an emergency suffix. A pension provider may have a separate code. Each employment or pension can have its own code, and the total outcome depends on how the records fit together.

How should employers handle the employee's information?

An employee should give the P45 or starter checklist information to the employer, but the employer must also use the payroll and HMRC coding instructions it receives. Employers should record the correct tax code and update it when HMRC sends a new notice. A manager's informal estimate of the employee's allowance is not a substitute for the official code.

The 2026/27 employer guidance lists 1257L W1, 1257L M1 and 1257L X as emergency codes from 6 April 2026. Payroll teams should select the code and basis that matches the HMRC instruction and the employee's pay frequency. Scottish and Welsh prefixes must be retained where HMRC includes them. The employer should not change the code simply because the employee believes a different code would produce a better net salary.

Frequently Asked Questions

This guide reflects HMRC and GOV.UK guidance available on 22 September 2026. Check your current coding notice, payslip and HMRC Income Tax account before acting. It is general information, not personal tax advice.

Official sources

• GOV.UK — Emergency tax codes
• GOV.UK — P9X tax codes from 6 April 2026
• GOV.UK — Understanding employees' tax codes
• GOV.UK — Starter checklist for PAYE
• GOV.UK — Rates and thresholds for employers 2026 to 2027