How long does emergency tax last?

For new employments: usually 1-2 pay periods, then auto-corrects. For pension lump sums: until you claim the refund via P55 (typical 30-day turnaround). If your code stays on emergency for 3+ pay periods, phone HMRC on 0300 200 3300.

Is W1, M1 or X the same as a BR code?

No — they're different. BR applies 20% to every pound with no allowance. W1/M1/X apply the normal bands and PA, but on a non-cumulative basis (just one period at a time, not year-to-date). You can be on 1257L W1 (emergency but with PA) or BR W1 (combined — rare).

Will HMRC automatically refund emergency tax on a pension lump sum?

Eventually — usually via a P800 letter the following tax year. Faster route: file form P55 immediately after the lump sum. HMRC refunds within 30 days typically. The P55 is at gov.uk under "Flexibly accessed pension payment: repayment claim".

Why is my tax code W1, M1 or X?

Last reviewed by the UK Tax Drag editorial team · 12 May 2026 · How we review · Next review due 12 May 2027 · See what changed · Report an error

5-minute read

W1, M1 and X are emergency tax-code suffixes. They tell PAYE to treat each pay period in isolation instead of looking at year-to-date earnings. W1 = weekly pay, M1 = monthly pay, X = non-standard pay period. Usually applied when starting a new job without a P45. The code is temporary and auto-corrects within 1-3 pay periods once HMRC has your full details.

How emergency codes differ from normal codes

Normal PAYE is cumulative. It looks at your total earnings since 6 April, calculates total tax due, and adjusts each pay period to make sure the right amount has been paid year-to-date.

Emergency W1/M1/X codes are non-cumulative. They just look at this pay period in isolation, apply the Personal Allowance for one period (e.g. £12,570 ÷ 12 = £1,047.50 for monthly), and tax the rest at the standard bands.

Comparison	Normal 1257L	Emergency 1257L W1/M1
Look at year-to-date earnings?	Yes — cumulative	No — only this period
Self-corrects across the year?	Yes	No — needs HMRC action
Refund overpaid tax automatically?	Yes (within tax year)	No (only after correction)
PA applied?	Full £12,570 spread evenly	£1,047.50/month (one period’s slice)

What W1, M1 and X each meanW1 = weekly pay frequency, M1 = monthly, X = irregular or non-standard (e.g. 4-weekly, fortnightly). They’re functionally identical — just labelled differently to match how often you’re paid.

Common reasons you're on emergency tax

You started a new job without giving your P45 to the new employer. The most common reason. HMRC defaults to W1/M1 until they receive details from the new employer.
You started a first-ever job. No P45 exists. The Starter Checklist establishes your tax position; until processed, emergency code applies.
You took your first pension. Pension providers use emergency M1 on the first payment because they have no record of your other income.
You drew a lump sum from a pension. The first taxable lump sum (above 25% tax-free) is taxed using emergency M1 — meaning a £20,000 withdrawal could see ~£8,000 of tax deducted instead of the actual £4,000-£5,000 owed.
You returned to UK from working abroad. HMRC doesn’t know your UK tax position immediately.

Worked example — first £30k payslip on emergency code

You start a new £30,000/yr job mid-tax-year (October). First monthly payslip:

	1257L cumulative (correct)	1257L M1 (emergency)
Gross this month	£2,500	£2,500
YTD earnings considered?	Yes (£15k from previous job + £2.5k now = £17.5k)	No (just £2,500)
PA used in this period	£1,047.50 (cumulative catch-up)	£1,047.50 (this period only)
Income tax this period	~£290	~£290
Difference	In this specific case, almost none

The emergency code usually doesn’t over-tax simple cases. It only causes problems when:

You had irregular earnings earlier in the year (e.g. high bonus, then nothing)
You took a large pension lump sum (the £8,000 vs £4,000 example above)
The emergency code persists for multiple periods, missing the cumulative reconciliation

Pension lump sums — where emergency tax really hurts

The single biggest pain point for emergency tax codes is pension lump sums. Take this scenario:

You’re 60 and have a £100,000 pension pot. You take £25,000 tax-free (25% PCLS), plus another £20,000 taxable as a lump sum. The provider taxes the £20,000 using emergency M1.

	Emergency M1	Correct calculation
Pension provider treats it as...	As if you earn £20k × 12 = £240,000/yr	Just this one £20,000 payment
PA in M1 period	£1,047.50	Full £12,570 (if no other income)
Tax calculated	~£8,030 (45% slabs apply)	~£1,486 (just basic rate on £7,430)
Net received	£11,970	£18,514
HMRC refund due	£6,544 — reclaimed via P55 form (or year-end P800)

The emergency tax refund checker walks through the reclaim. Use form P55 (income flexibly accessed) at gov.uk for fastest refund.

How emergency codes self-correct

For new employments — usually automaticOnce your employer files the Full Payment Submission (FPS) to HMRC at the end of the first pay period, HMRC matches your record. Within 1-2 pay periods, HMRC issues a proper cumulative code (e.g. 1257L without W1/M1). The next payslip catches up overpaid tax via cumulative reconciliation.

For pension lump sums — usually requires P55Pension providers can’t self-correct because there’s no future pay period. You must claim using form P55 (or P50Z if you’ve taken the whole pot, or P53Z if you’re continuing to draw down). HMRC refunds within 30 days typically.

For persistent emergency codes — phone HMRCIf your code shows W1/M1 for more than 3 pay periods, phone HMRC on 0300 200 3300 with your NI number and last payslip. They can issue a corrected code directly to your employer.

Claim back emergency tax fast

The emergency tax refund checker shows the right form (P55, P50Z, P53Z or P800) and the timeline for getting your refund from HMRC.

Open the refund checker →

Other UK tax codes explained

Sources and methodology

Emergency code rules from gov.uk/tax-codes/emergency-tax-codes. P55, P50Z, P53Z forms at gov.uk. Starter Checklist at gov.uk/government/publications/paye-starter-checklist.

UK Tax Drag is not authorised by the Financial Conduct Authority and does not provide regulated financial advice — see the content disclaimer for the full position. The methodology page documents how every calculator is built and reviewed.

Editorial accountability

Open Trust Centre →

Every page is reviewed against the editorial standards, written from primary sources, sourced openly, and corrected publicly. No affiliate revenue. No sponsored content. No paid placements.

Editorial standards Editorial process Corrections policy How we make money Editorial team Methodology