How does an emergency tax code work and how do I get it fixed?

Full answer

Emergency tax codes are common when starting a new job, and while the name sounds alarming, they are usually a temporary, self-correcting situation rather than a permanent problem, provided the right information reaches HMRC and your employer promptly. **What the code looks like and means** For 2026/27, an emergency tax code is typically shown as 1257L W1, 1257L M1, or 1257L X -- the "1257L" part gives you the standard £12,570 Personal Allowance (the same as most people's normal code), but the W1 (week 1), M1 (month 1), or X suffix means it is applied on a NON-CUMULATIVE basis, calculating tax on that single pay period in isolation, rather than accounting for your total pay and tax so far in the tax year the way a normal cumulative tax code does. **Why this can lead to over- or under-taxation** Because each pay period is assessed in isolation under an emergency code, if your income varies during the year, or if you started the job partway through the tax year with some unused Personal Allowance from earlier months, a non-cumulative emergency code can result in you paying MORE tax than you should in that period (since it does not account for allowance you have not yet used), which then needs to be corrected once your code is updated. **Common reasons for being put on an emergency code** - Starting a new job without a P45 from your previous employer (perhaps because you have not received it yet, or because this is your first ever job) - Starting a job as a second job or after previously being self-employed, without clear information about other income HMRC needs - Coming back to work after a period not working, where HMRC has not yet processed updated information **How it gets corrected** Once your new employer submits your starter details to HMRC (via a starter checklist if you have no P45, or your P45 information if you do), and HMRC processes this alongside any other income information they hold, HMRC issues an updated, correct tax code, which your employer then applies going forward. If you were overtaxed under the emergency code before the correction, a cumulative code afterwards will usually automatically refund the excess tax through your payslip over subsequent pay periods, without you needing to do anything separately, though a correction after the tax year has ended may require you to claim a refund directly from HMRC. **What you can do to speed up the correction** Provide your new employer with your P45 from your previous job as soon as possible, or complete a new starter checklist accurately (including correctly stating whether this is your only job, and if not, providing details of other income) -- giving accurate, prompt information is the main lever you have to minimise how long you remain on an emergency, non-cumulative code. **Worked example** Someone starts a new job in June without a P45 (having mislaid it from a previous employer) and is placed on a 1257L M1 emergency code. For the first two months, tax is calculated on each month's pay in isolation, without accounting for the two months of unused Personal Allowance from April and May, resulting in slightly higher tax deducted than their correct annual liability would suggest. Once HMRC processes the correct cumulative code in August, the following payslip factors in the full year's Personal Allowance to date, automatically refunding the earlier overpaid tax through that month's pay. **Practical tip** Check your payslip and tax code every time you start a new job or notice an unfamiliar code, and use HMRC's online tax checker or personal tax account to confirm whether your code is correct -- most emergency code situations resolve automatically within one to three pay periods once accurate information reaches HMRC, but it is worth checking rather than assuming it will sort itself out indefinitely.

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