UK tax codes · 2026/27 tax year

Emergency tax codes: 1257L W1, M1 and X

A tax code ending in W1, M1 or X, or NONCUM on your payslip, is an emergency tax code. Your tax is worked out on each week's or month's pay on its own, as if it were the first payday of the tax year, so you do not get back any tax-free allowance you did not use earlier. Start a £25,000 job in October with no pay since April and 1257L M1 takes about £1,243 by 5 April, when the normal cumulative code would take £0.

Tax code rules checked against GOV.UK and HMRC's PAYE Manual on 25 September 2026.

Weekly

e.g. 1257L W1

Monthly

e.g. S875L M1

Pay dates vary

e.g. C663L X

Overpaid on £25k

£1,243

starting in October

Starting a job in October on 1257L M1

Paid monthly from 6 October to 5 April (6 months), with no other pay since 6 April. Month 1 basis versus the normal cumulative basis, England, Wales and Northern Ireland rates.

Salary	Pay earned by 5 April	Tax on M1 basis	Tax on cumulative basis	Taken too much
£25,000	£12,500	£1,243.02	£0	£1,243.02
£40,000	£20,000	£2,743.02	£1,486	£1,257.02
£60,000	£30,000	£5,716.02	£3,486	£2,230.02

Same pay from April: no difference over the year

If you are paid the same every month for the whole tax year, the month 1 basis takes the same total as plain 1257L.

Salary	Tax a month on M1	M1 over 12 months	Tax on 1257L
£25,000	£207.17	£2,486	£2,486
£40,000	£457.17	£5,486	£5,486
£60,000	£952.67	£11,432	£11,432

Why you get one

Usually because your new employer does not have your previous pay and tax details when they first pay you. You might also be put on one when you start getting company benefits or the State Pension; GOV.UK says that is normal and you keep it until the end of the tax year.

Cumulative versus week 1 / month 1

Normally your employer looks at all your pay and tax since 6 April, gives you a share of your allowance for each month that has passed, and refunds tax if you have paid too much. HMRC's PAYE Manual says the week 1 / month 1 basis ignores previous pay and tax, which is why it cannot give you refunds for months you were not working.

Hand over your P45

If you have a P45 from your last job, give it to your new employer; it holds your pay and tax so far and can take you off the emergency code. If your old employer did not give you one, ask them. HMRC usually updates your code within 35 days of you starting.

Getting overpaid tax back

Once HMRC has your details, it sends a new code and asks your employer to refund the difference through your pay, usually when the new code is first used. If that does not happen before 5 April, HMRC checks your tax after the year ends and tells you how to get a refund.

If you think this code is wrong

If you started more than 35 days ago and are still on W1, M1 or X, check your details. Sign in to HMRC's Check your Income Tax service (gov.uk/check-income-tax-current-year) and check your jobs, pensions, benefits and expenses. HMRC then tells you and your employer any new code within 15 working days; it should show on your next or following payslip if you are paid monthly, or your third if weekly. If you cannot go online, call the Income Tax helpline on 0300 200 3300 (Monday to Friday, 8am to 6pm). After starting a new job, wait 35 days before calling.

Guides and definitions

High Income Child Benefit Charge: how it is worked out and cut (Guide)
How to read your payslip: every line explained, with an example (Guide)
Emergency tax: how it works and how to get your money back (Guide)
Emergency tax code (An emergency tax code, marked W1, M1 or X, taxes each payday on its own, as if you were paid that amount every period of the year.)
P11D (A P11D is the form UK employers send HMRC by 6 July to report each employee's taxable benefits and expenses that were not taxed through payroll.)
P60 (A P60 is the yearly summary of your pay and tax from one employer, due by 31 May if you work there on 5 April.)
Personal Allowance (The Personal Allowance is the income you can earn each UK tax year before Income Tax starts: £12,570 for 2026/27.)
Tax code (A UK tax code tells your employer or pension provider how much tax-free pay to give you; 1257L, meaning £12,570, is the most common.)

Check your own tax code and pay

Other tax codes explained

1257L tax code (Standard tax-free allowance of £12,570 on one job or pension)
S1257L tax code (Standard allowance, taxed at Scottish rates)
C1257L tax code (Standard allowance, taxed at Welsh rates)
1257M / 1383M tax code (You receive £1,260 of Marriage Allowance from your partner)
1257N / 1131N tax code (You transfer £1,260 of Marriage Allowance to your partner)
BR tax code (All pay taxed at the 20% basic rate, no allowance)
0T tax code (No tax-free pay; all pay taxed through the bands)
D0 tax code (All pay taxed at the 40% higher rate)
D1 tax code (All pay taxed at the 45% additional rate)
SD0, SD1, SD2, SD3 tax code (Scottish flat-rate codes at 21%, 42%, 45% or 48%)
K codes tax code (Untaxed income or deductions bigger than your allowance)
NT tax code (No tax taken from this job or pension)

Every UK tax code in one table · Salary after tax calculator · Check your own tax code and pay

Common questions

How do I know if I am on an emergency tax code?

Look at the end of your code. W1 (weekly pay), M1 (monthly pay) or X (pay dates vary) mean emergency, for example 1257L W1 or 1257L M1. Some payroll software shows NONCUM instead. If your code ends in none of these, you are not on an emergency code.

How long does an emergency tax code last?

For a new job, HMRC usually sends a proper code within 35 days of you starting, once it has details from your old and new employers. If you have not paid enough tax, you stay on it until you have. For company benefits or the State Pension it lasts until 5 April.

Do you pay more tax on an emergency tax code?

Only in some cases. With the same pay every month from April the total is the same. If you start mid-year it can be much more: on a £40,000 salary from October, 1257L M1 takes £2,743 by April against £1,486 on the normal basis.

Will I get emergency tax back?

Yes, once HMRC has your income details. It updates your code and your employer refunds the difference in your pay, usually on the first payday using the new code. Anything still owed after 5 April is sorted when HMRC checks the year.

Is 1257L X an emergency tax code?

Yes. X is used when your pay dates vary, rather than a fixed week or month. It works the same way as W1 and M1: each payment is taxed on its own without looking at what you earned earlier in the tax year.

Sources and assumptions

Income Tax for the 2026/27 tax year (6 April 2026 to 5 April 2027), with the same pay every payday for the whole year.
The code number is read as GOV.UK describes it: the tax-free amount with the last digit dropped (1257 = £12,570). Payroll tables can differ by a few pounds.
National Insurance, pension contributions and student loans are not included unless a table says so.
The October examples use tax months 7 to 12 and divide the yearly allowance and bands by 12 each month, before rounding each month to the penny.

These are estimates to help you read your tax code, not tax advice. HMRC and your employer's payroll decide the tax you actually pay.