Emergency Tax Code: What It Means and How to Fix It

What is an emergency tax code?

An emergency tax code is a temporary code HMRC uses when your employer does not have enough information to tax you correctly. Instead of working out your tax on everything you have earned so far in the tax year, it taxes each week or month on its own, as if you earned that amount all year. That is why it so often takes too much.

You can spot one on your payslip. The code ends in W1 if you are paid weekly, M1 if monthly, or X if your pay dates vary — 1257L W1 and 1257L M1 are the most common. Some payslips show NONCUM instead, which means the same thing. If your code ends in any of those, you are on an emergency code.

The key point: W1 and M1 do not remove your Personal Allowance. A 1257L M1 code still gives you £1,047.50 of tax-free pay a month — a twelfth of the £12,570 allowance for 2026/27. What it does not do is look backwards. Pay you received, or allowance you did not use, earlier in the year is invisible to it. That is where the overpayment comes from.

Why you get one

The most common reason is starting a new job. When you leave a job, your old employer gives you a P45 showing what you earned and how much tax you paid, and your new employer uses it to put you on the right cumulative code. Without a P45 — because the old employer has not sent it, or you came from self-employment or from abroad — your new employer must use an emergency code until HMRC supplies the details.

If you have no P45, your employer should ask you to complete a Starter Checklist (formerly a P46). Your answers tell HMRC whether this is your only job and whether you have other income, and HMRC then issues a proper code. Starting company benefits or the State Pension can also put you on an emergency code — in that case it usually stays until the end of the tax year.

Why it takes too much tax

Normal PAYE is cumulative: each time you are paid, your employer looks at everything you have earned since 6 April and everything you have paid so far, and taxes only the difference. An emergency code cannot do that, because it does not know your earlier earnings — so it treats each month as a standalone year.

Take someone who starts a job in October on £3,000 a month. On the correct cumulative code, the first payslip would show no tax at all — seven months of unused allowance, £7,332.50, is waiting to be used, and the £3,000 earned so far sits well inside it. On 1257L M1, the same payslip shows £390.50 of tax, because only one month's allowance counts. The money is not lost — it comes back once the code is fixed — but take-home pay is lower for a month or two.

How to fix it

Start with your employer: give them your P45 as soon as you have it, or complete the Starter Checklist if you have none. Once HMRC has details from both employers, it issues a corrected code — usually within 35 days of starting.

If 35 days have passed and the code is still wrong, do not wait. Sign in to your Personal Tax Account on GOV.UK and check the code HMRC holds for you, or update your details through the Check your Income Tax service. Phoning HMRC also works, but the online route is faster and leaves a record.

Once the correct cumulative code reaches your employer, payroll refunds the overpayment automatically in your next pay — you do not need to claim it. It appears as less tax, sometimes no tax at all, on the next payslip or two, until the year-to-date figures catch up.

What if it is not fixed by the end of the tax year?

If 5 April passes and the code was never corrected, HMRC reconciles your tax after the year ends. It compares what you paid with what you owed, and if you overpaid it sends a P800 tax calculation, usually between June and October, with a refund. You can also claim through your Personal Tax Account. Either way, the money comes back — but it can take months, which is why fixing the code in-year is worth doing. Keep your payslips and P60 — if HMRC's figures disagree with yours, those settle it.

BR and 0T are not emergency codes

Two codes are often confused with emergency codes, and the confusion costs people money. BR means all the income from that job is taxed at 20%, with no Personal Allowance at all. It is the correct code for a genuine second job or a second pension — but if it appears on your main job, you are being overtaxed and should tell your employer.

0T is harsher still: no allowance, and your income is taxed through the normal bands, so some of it can fall into the 40% rate. D0 and D1 do the same at 40% and 45% for higher and additional-rate taxpayers with second incomes. None of these is an emergency code, and none is fixed by waiting — they change only when HMRC is told the job is your main one.

An emergency tax code is a nuisance, not a lasting problem. Check your first payslip, hand over your P45 or complete the Starter Checklist, and watch the code for the next month. If it is still wrong after 35 days, chase it through your Personal Tax Account. The tax you overpay is yours, and the system is built to give it back — the sooner the code is right, the sooner it does.