Few things are more frustrating than opening your first payslip from a new job and finding a chunk of your wages missing. More often than not the cause is emergency tax. It is not a penalty and it does not mean you have done anything wrong, but it can leave you short for a while. This guide explains what emergency tax is in the 2026/27 tax year, why you have been put on it, how much extra it costs, and exactly how to get any overpayment back.
What is emergency tax?
Emergency tax is a temporary way of taxing your pay when HMRC does not yet have enough information to give you the correct tax code. Normally your tax code looks at your income across the whole tax year, so your tax free personal allowance is spread evenly across your paydays. An emergency code cannot do that. Instead it taxes each payday on its own, as though that single pay packet were a slice of a much larger annual income, which often means too much tax comes out.
The emergency tax codes
You can spot emergency tax from your code, which appears on your payslip. The most common emergency code is your normal code with the letters W1, M1 or X added, for example 1257L W1, where W1 stands for week one and M1 for month one. These give you the personal allowance but only for that pay period rather than across the year. In some cases, particularly where you have started a job without any details, you may be put on the code 0T, which gives no personal allowance at all and usually takes the most tax, or BR, which taxes everything at the basic rate of 20%.
Why you have been put on emergency tax
There are several common triggers. The most frequent is starting a new job without handing over a P45 from your last employer, so the new employer has nothing to go on. It also happens when you start your very first job, when you begin receiving a company or private pension, when you take on a second job, or when you return to work after a spell of self employment or time away. In each case HMRC simply does not yet have a full, up to date picture of your income, so it applies an emergency code until it does.
How much extra do you pay?
How much you overpay depends on which emergency code you are on and how your pay is spread through the year. With a week one or month one code you still get your tax free allowance for that period, so the overpayment may be modest. With a 0T or BR code the effect can be much larger, because you lose your allowance or have everything taxed at 20% regardless of how little you have earned so far in the year. People taking a one off pension lump sum are often hit hardest, because the emergency code can treat that single payment as if it were repeated every month.
A simple worked example
Suppose you start a new job on a 0T month one code and your first month pay is £2,500. Instead of getting a slice of your £12,570 personal allowance against it, the code gives you nothing tax free, so the whole £2,500 is taxed. Once HMRC issues your correct code, the system recalculates, gives you the allowance you were due, and the extra tax already taken is refunded through your following payslips.
How to get off emergency tax
The quickest fix is to make sure your employer has the right information. If you have a P45 from a recent job, hand it to your new employer straight away. If you do not have one, your employer will ask you to complete a starter checklist, which tells HMRC about your situation. Once HMRC has what it needs, it sends your correct code to your employer, who applies it on your next payday. You can speed things up by checking and updating your details in your Personal Tax Account on the HMRC website.
How to claim back overpaid emergency tax
In most employment cases you do not need to do anything to get your money back. Once your correct code is in place, your employer recalculates your tax for the year so far and the overpayment is repaid automatically through your wages, often in the very next pay run. If the tax year ends before it is sorted out, HMRC sends a P800 calculation and you can claim the refund online. Pension lump sums work differently, and you may need to complete a specific HMRC form, such as a P55, P53Z or P50Z depending on your circumstances, to reclaim the tax sooner rather than waiting until the year end.
How long does it take?
If the cause is simply a missing P45 or starter checklist, the correct code usually arrives within a pay period or two once the information reaches HMRC, and the refund follows automatically through your pay. A refund claimed on a pension lump sum form is typically processed within a few weeks. Keeping your contact and bank details current in your Personal Tax Account helps avoid any delay.
How to avoid emergency tax
You cannot always avoid it, but you can shorten it. Always pass your P45 to a new employer, or complete the starter checklist promptly if you do not have one. Check your tax code on your first payslip and act quickly if it carries W1, M1, X, 0T or an unexpected BR. The faster HMRC has the right information, the sooner your code is corrected and your money returned.
Frequently asked questions
What does emergency tax code 1257L W1 mean?
It gives you the standard personal allowance but only for that single pay period rather than across the whole year, so you may pay a little too much tax until your code is corrected.
Will I get my emergency tax back?
Yes. In most employment cases the overpayment is refunded automatically through your wages once your correct code is in place, or after the year ends through a P800. Pension lump sums may need a specific HMRC reclaim form.
Why am I on emergency tax?
Usually because HMRC does not yet have full details of your income, often after starting a job without a P45, starting your first job, taking a second job or beginning a pension.
How do I stop being on emergency tax?
Give your new employer your P45 or complete a starter checklist, and check your details in your Personal Tax Account, so HMRC can issue your correct code.