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 (week one, month one, or generic emergency).

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• Returning to work after a gap — long sickness, maternity, sabbatical — where HMRC's records are out of date.
• Large lump-sum payment (redundancy, bonus, pension drawdown lump sum) where PAYE cannot reasonably apply your normal cumulative position.
• Pension drawdown's first payment almost always uses an emergency code, because the provider has no other record of your year's earnings.

The pension drawdown emergency-tax problem

This is the single most common reason people end up over-paying tax: 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 £30,000 single drawdown can be taxed as if it were £360,000 of annual income, leading to a refund-due position of £5,000 to £10,000.

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 receives your starter information from the new employer (typically by the second or third payslip), they issue an updated cumulative tax code — usually the standard 1257L for 2026/27. That cumulative code looks at your year-to-date earnings and adjusts the next month's tax to bring you back on track. Any over-deduction reverses out within a month or two for ordinary salary cases.

If the tax year ends and you are still on an emergency code, HMRC issues a P800 reconciliation. Refunds are usually paid by cheque or BACS within a few weeks of the P800.

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. HMRC then issues a revised code to your employer electronically, usually within a few days.
• 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) but cannot provide a P45, so payroll uses 1257L M1. Because it is non-cumulative, each month they get only 1/12th of the allowance and a single month’s tax bands, which broadly works — but it ignores the three unused months of allowance (April, May, June) they accumulated before starting.

Once HMRC sends the employer a cumulative 1257L code, payroll recalculates the year to date. The roughly £3,140 of Personal Allowance from those three earlier months is now set against their pay, so the next payslip collects noticeably less tax — often a few hundred pounds less — until the year-to-date position is corrected. The refund arrives automatically 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. A refund on a P800 is usually paid by bank transfer if you claim it online, or by cheque otherwise, typically within a few weeks. 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.