TL;DR: An "emergency tax code" in the UK is a temporary PAYE code applied when HMRC does not yet have enough information to issue the right cumulative code. The three you will see most often are 1257L W1 (weekly payroll), 1257L M1 (monthly payroll), and 1257L X (a generic non-cumulative marker). Each gives the standard 12,570-pound personal allowance, but on a "this pay period only" basis rather than spread across the year-to-date, which usually means too much tax is deducted at the start. HMRC normally fixes the code once it receives the year-to-date pay information through Real Time Information (RTI) submissions or a P45, after which any overpayment is refunded through the next pay packet (under the new cumulative code) or after year-end through a P800 reconciliation. Pension flexible-access lump sums often get the more punitive 0T or BR code instead, producing very large refunds that can be reclaimed through forms P53Z, P55 or P50Z.
Last reviewed May 2026
"Emergency tax code" is an informal description used by HMRC and employers for several non-cumulative PAYE tax codes. The label is unhelpful because it covers a few different codes with different effects. What they have in common is that they are applied as a temporary measure when the year-to-date tax position is uncertain.
This guide explains which codes HMRC and employers actually call "emergency", how each one operates, why one is issued in the first place, what the practical effect on a payslip is, and how to get back to a normal cumulative code with any overpayment refunded.
The codes commonly called "emergency"
The standard "emergency tax code" for a new starter who has not provided a P45 is 1257L on a week 1 / month 1 basis. On payslips it appears as 1257L W1 (weekly payrolls), 1257L M1 (monthly payrolls), or 1257L X (a generic non-cumulative marker used by some payroll systems). The "L" indicates entitlement to the standard personal allowance. The 1257 represents the annual tax-free amount of 12,570 pounds (1257 multiplied by 10).
The "W1 / M1 / X" suffix is the operating basis. It tells the employer not to use the year-to-date cumulative calculation. Each pay period is treated in isolation, with one twelfth of the personal allowance and one twelfth of the basic and higher rate bands applied to that period's pay. The full year-to-date is ignored.
HMRC's PAYE manual sometimes describes other codes (BR, 0T, D0) as "emergency" in particular contexts. BR taxes all income at the basic rate with no allowance. 0T applies no allowance and taxes through the standard bands. D0 taxes everything at the higher rate. These are not the standard new-starter emergency codes but they crop up after a P45 has been issued, on second jobs, or on pension flexible-access lump sums where HMRC has had no prior information about the recipient's overall income.
Why an emergency code is issued
The most common trigger is a new job started without a P45 from the previous employer in the same tax year. The new employer cannot apply a cumulative code because it does not know the year-to-date pay and tax. To avoid the risk of an unintended refund or undercharge, the employer applies 1257L on a week 1 or month 1 basis pending HMRC confirmation of the right cumulative code.
The HMRC new starter checklist asks the employee three questions: is this their only job, have they had another job in this tax year, and do they receive a state or occupational pension. The answers (statements A, B, and C in older versions of the form) drive which code the employer applies pending HMRC's instruction. Statement A (only or main job, no previous job this year, no pension) gets 1257L cumulative. Statement B (previous job this year, no P45) gets 1257L W1 / M1. Statement C (a second job or pension already in payment) gets BR.
A pension flexible-access lump sum (under pension freedoms introduced in April 2015) is the other big source of emergency tax. The pension provider applies an emergency code to the first payment because it has no information from HMRC about the recipient's other income. The emergency code is usually 1257L on month 1, but it can produce a very large over-deduction because the lump sum is treated as if 12 such payments were going to be made across the year. HMRC's reclaim forms (P53Z, P55 and P50Z) exist specifically to refund this overpayment quickly.
What it does to a payslip
For a new starter on a monthly payroll with the standard 1257L M1 code, the calculation is: take this month's gross pay, deduct one twelfth of the personal allowance (1,047.50 pounds), and apply the basic rate (20 percent) up to one twelfth of the basic-rate band, then higher rate (40 percent) above that. Year-to-date is ignored.
For an employee starting mid-year with no income earlier in the tax year, the result is more tax deducted than a cumulative code would have produced. Under a cumulative 1257L, six months of unused allowance would have been available to offset the first month's pay; under the M1 version only one month is available. The overpayment can be substantial for higher-paid new starters.
For an established employee already on a 1257L cumulative code with steady monthly pay, the two methods produce identical monthly tax. The M1 effect only diverges from cumulative when the pay pattern is uneven.
Getting off the emergency code
Three routes typically take an employee from an emergency code to a cumulative one. The first is HMRC issuing a new code automatically. Once the previous employer has filed their final RTI return and any P45 has been processed, HMRC writes to the new employer (and to the employee) confirming the right cumulative code. This usually takes a few weeks but can be longer.
The second is handing in a P45 to the new employer. The P45 contains the year-to-date pay and tax, the previous code, and the leaving date. The new employer can apply the cumulative version of the code immediately, picking up any year-to-date refund or extra tax in the next pay packet.
The third is contacting HMRC directly. The personal tax account on GOV.UK allows an individual to update their job and income information online. HMRC issues a new code to the employer with a reference number, and the next pay date picks up the change.
Emergency tax on pension flexible-access lump sums
The treatment of a first pension flexible-access lump sum (often a tax-free lump sum plus a taxable element, taken under the pension freedoms) is a particular sore point. The pension provider applies an emergency tax code on a month-1 basis to the taxable element. The HMRC system "annualises" the payment: it treats the lump sum as if 11 more such payments were to come, which pushes the calculation into higher and additional rate territory.
The result is normally far too much tax taken. HMRC publishes three reclaim forms for this scenario: form P53Z (where the pension pot is fully encashed and the saver has other income in the tax year), form P55 (where part of the pot has been taken and there is no continuing employment), and form P50Z (where the pot is fully encashed and there is no other income). Each form produces a refund within around 30 working days of HMRC receiving the completed form.
Alternatively, if the saver does not complete a reclaim form, HMRC will reconcile the position automatically through a P800 calculation after the tax year ends, but that takes several months longer.
Year-end reconciliation if the emergency code stays on
If the emergency code remains in place through the tax year and the employee has paid too much tax overall, HMRC reconciles the position after 5 April through a P800 calculation. The P800 matches the year-to-date totals from each employer's RTI returns against HMRC's records, calculates the correct annual tax, and issues a refund.
P800 refunds are normally issued between June and October following the end of the tax year. They can be claimed by bank transfer through the personal tax account on GOV.UK or paid by cheque if the online claim is not made within a set window.
Where the P800 shows extra tax due (less common with a 1257L emergency code, more common with BR or 0T applied to a second job that has now ended), HMRC issues a simple assessment and the underpayment is normally coded into the next year's tax code.
How we verified this
The structure of UK PAYE tax codes, the use of cumulative and non-cumulative operation, and the application of the W1 / M1 / X suffixes reflect the HMRC PAYE manual and current GOV.UK guidance on tax codes. The new starter checklist process and the application of BR and 0T codes after a P45 has been issued reflect current HMRC PAYE rules. The pension flexible-access emergency tax treatment and the P53Z, P55 and P50Z reclaim forms reflect HMRC guidance for the current tax year and the legislation made under Finance Act 2014 introducing the pension freedoms. P800 reconciliation reflects current GOV.UK guidance. No specific phone numbers, FCA or HMRC reference numbers have been invented.
Disclaimer: This article is general information about UK PAYE emergency tax codes. It is not personal tax advice. Tax codes are issued by HMRC based on individual circumstances and the right code in any particular case depends on the specific income sources, allowances and reliefs in point. Anyone unsure about their code should check the personal tax account on GOV.UK or contact HMRC directly.
Frequently asked questions
What is the emergency tax code in the UK?
The standard emergency tax code is 1257L applied on a week 1 (W1), month 1 (M1) or generic non-cumulative (X) basis. It gives the standard 12,570-pound personal allowance but treats each pay period in isolation rather than as part of a cumulative year-to-date calculation. The code is normally applied to new starters who have not produced a P45.
How long does emergency tax last?
Usually a few weeks. HMRC issues the correct cumulative code once it has the year-to-date information from the previous employer's RTI returns or from a P45 handed in to the new employer. Handing in a P45 or contacting HMRC through the personal tax account speeds the process.
How do I claim back emergency tax?
If the emergency code is replaced by a cumulative code during the tax year, the next pay packet picks up any year-to-date refund automatically. If it stays on until year-end, HMRC reconciles the position through a P800 calculation after 5 April and pays any refund through the personal tax account or by cheque. Pension flexible-access overpayments can be reclaimed faster using forms P53Z, P55 or P50Z.
Why is my tax code 1257L W1 instead of 1257L?
The W1 suffix means the code is being operated on a week 1 (non-cumulative) basis. Each pay week is treated in isolation. The most common reason is that you started a new job without providing a P45 from your previous employer in the same tax year, so HMRC does not yet have the year-to-date information to apply a cumulative code.
What is the difference between 1257L W1 and 1257L M1?
The only difference is the payroll frequency. W1 (week 1) is used on weekly payrolls; M1 (month 1) is used on monthly payrolls. Both are non-cumulative versions of the 1257L standard personal-allowance code. The X suffix is a generic alternative used by some payroll systems and means the same thing.
