What is an emergency tax code?

The technical definition

An emergency tax code is a temporary code HMRC applies when an employer cannot calculate your tax position properly because they don't yet have your full tax history. The most common emergency codes are 1257L W1, 1257L M1, or 1257L X — the W1, M1, or X suffix flags that the code is being applied on a non-cumulative basis. GOV.UK says W1 is used when you’re paid weekly, M1 when you’re paid monthly and X when your pay dates vary; some payslips show NONCUM instead (GOV.UK, emergency tax codes).

Non-cumulative means the employer treats each pay period in isolation, applying 1/12th of the annual Personal Allowance each month, rather than year-to-date totals. The result is that you usually pay roughly the right amount of tax for any given month — but the system cannot self-correct for unusual earnings patterns within the year.

Why it appears

• New job without a P45. If you cannot give your new employer the P45 from your previous job (or you don't have one because it's your first job), they apply an emergency code based on the new starter checklist alone.
• Returning to work after a gap — long sickness, maternity, sabbatical — where HMRC's records are out of date.
• Starting State Pension or taxable benefits. GOV.UK says this can put you on an emergency code for the rest of that tax year, with a normal code from the next one.
• A pension drawdown or other flexible payment. HMRC’s PAYE Manual says providers use the emergency code on a week 1 or month 1 basis for the first payment (PAYE94055). A bonus or redundancy payment from your existing employer does not by itself change your code: it goes through the code you already have under PAYE.

The pension drawdown emergency-tax problem

Pension withdrawals are where emergency tax can cost most: when you take your first taxable pension lump sum, the provider applies a Month 1 emergency code that effectively assumes you'll take the same lump every month for the rest of the year. A single £30,000 taxable withdrawal is treated as one month of £360,000-a-year income: after one month’s allowance (£1,047.50), slices are taxed at 20%, 40% and 45%, so about £11,880 is deducted. Someone with no other income in 2026/27 owes (£30,000 − £12,570) × 20% = £3,486 on it, leaving about £8,390 to reclaim. With a salary as well, less is due back, because more of the withdrawal really falls in the higher bands.

HMRC reconciles the over-deduction at year-end via P800, but the cashflow gap can sting. The pension drawdown tax calculator shows the size of the typical emergency-tax hit, and you can apply for an in-year refund using HMRC forms P55, P53Z, or P50Z depending on your circumstances.

How emergency tax usually corrects itself

Once HMRC has your details from your new and previous employers, it issues an updated cumulative tax code — usually the standard 1257L for 2026/27. GOV.UK says this can take up to 35 days from when you start the job. That cumulative code looks at your year-to-date earnings and adjusts the next payslip’s tax to bring you back on track, so for ordinary salary cases the over-deduction comes back through pay.

If the tax year ends and you are still on an emergency code, HMRC sends a P800 tax calculation. GOV.UK says a refund claimed online arrives within 5 working days; if the letter says a cheque is coming, it arrives within 14 days of the date on the letter (GOV.UK, if you’re due a refund).

Related on this site

Decode any code (emergency or otherwise) with the tax code decoder, check whether you're owed a refund using the emergency tax refund checker, and see the impact on a pension lump sum with the pension drawdown tax calculator.

What W1, M1 and X usually mean

These markers usually mean week 1 or month 1 treatment. Payroll gives you only one slice of allowance and tax bands for the current pay period instead of using the normal cumulative position across the tax year.

Why it happens

• No P45 reached payroll in time.
• The starter checklist is still incomplete or not processed.
• You changed jobs, had a break, or payroll could not match the record cleanly.

Best next pages

Use Emergency Tax and Refund Checker to estimate whether too much tax may already have been taken, then use Why is my tax code BR? or the GOV.UK tax-code page if the code is something different.

Official sources: emergency tax codes and PAYE starter checklist guidance.

The codes you might see — and what each one means

“Emergency tax” is a loose term covering several different codes. Knowing which one you have tells you whether you are being taxed roughly right or heavily over-taxed:

• 1257L — the standard code for 2026/27, giving the full £12,570 Personal Allowance. On its own (cumulative) it is not an emergency code at all. It only becomes one when a W1, M1 or X suffix is attached, which switches it to non-cumulative.
• BR (“basic rate”) — taxes all of that income at 20% with no Personal Allowance. Common and usually correct on a second job or pension, where your allowance is already used against your main income.
• 0T — no Personal Allowance and taxes income across the normal bands (20%, then 40%, then 45%). Applied when HMRC has no details at all, or when your allowance is fully used elsewhere. Harsher than BR for higher earners because it reaches the 40% band.
• D0 and D1 — tax everything at 40% (D0) or 45% (D1) respectively, typically for a second source of income for someone already a higher- or additional-rate taxpayer.

The key practical point: a W1/M1 code gives you a slice of allowance each period and so over-taxes you only modestly, whereas BR, 0T, D0 and D1 give you no allowance against that income and can over-tax you significantly if they have been applied in error.

How to fix an emergency tax code

An emergency code will often correct itself within a payslip or two, but you can speed it up and avoid waiting months for money back:

• Give your employer your P45. The single most effective step. Parts 2 and 3 of the P45 from your previous job tell the new payroll your pay-to-date and tax-to-date so they can switch you to a cumulative code. No P45? Complete the HMRC starter checklist accurately — ticking the wrong statement (for example, saying it is your only job when it is your second) is a frequent cause of a wrong code.
• Check and fix it in your Personal Tax Account. Sign in to the HMRC app or your Personal Tax Account, where you can see your current code, view how it was worked out, and tell HMRC about a second job ending or an incorrect benefit. GOV.UK says HMRC then tells you and your employer the new code within 15 working days; if you have just started the job, it asks you to wait 35 days before contacting it (GOV.UK, if you think your tax code is wrong).
• Call HMRC on the income tax helpline if the code is clearly wrong and time-sensitive (for example a large bonus is imminent). Have your National Insurance number and employer PAYE reference ready.

You cannot change your own tax code directly — only HMRC can — but giving payroll the right starter information, or correcting your details online, is what triggers the change.

How overpaid tax comes back — a worked example

Consider a new starter who joins an employer in July on a salary of £30,000 a year (£2,500 a month), with no other job or taxable benefits since 6 April. On HMRC’s starter checklist that is statement A, which gives the full allowance on a cumulative basis from the first payday. Suppose statement B is ticked instead (it is meant for someone who has had another job or taxable benefits since 6 April), so payroll uses 1257L M1 until HMRC confirms the details (HMRC, PAYE starter checklist). Because it is non-cumulative, each month they get only 1/12th of the allowance (£1,047.50) and a single month’s tax bands, so July’s tax is (£2,500 − £1,047.50) × 20% = £290.50 — but it ignores the three unused months of allowance (April, May, June).

Once HMRC sends the employer a cumulative 1257L code, payroll recalculates the year to date. The £3,142.50 of Personal Allowance from those three earlier months (3 × £1,047.50) is now set against their pay, so over the following payslips they pay about £628 less tax in total (20% of £3,142.50). If the new code is used from August, that payslip refunds July’s £290.50 and takes no tax for August (£581 less than on M1), and the last £47.50 comes off September’s tax. The refund arrives through payroll; there is nothing to claim.

If the tax year ends (5 April) before the code is fixed, HMRC reconciles everything after year end and issues a P800 calculation showing the over- or under-payment. GOV.UK says a refund claimed online arrives within 5 working days, and a cheque within 14 days of the date on the letter. For an over-taxed pension lump sum specifically, you do not have to wait for the P800 — you can reclaim in-year using HMRC form P55, P53Z or P50Z depending on whether you have emptied the pot and whether you have other income.