Emergency Tax Calculator UK 2025/26

What Is Emergency Tax?

Emergency tax is a temporary tax code that HMRC applies when your employer doesn't have enough information to calculate your tax correctly. This typically happens when you start a new job, begin receiving a company pension, or your employer hasn't received your P45 from a previous role. The result is that you usually pay more tax than you should each month until HMRC corrects your code.

The most common emergency tax code for 2025/26 is 1257L W1 (weekly) or 1257L M1 (monthly). The "W1" or "M1" suffix means your tax is calculated on a non-cumulative, week-by-week or month-by-month basis. Your pay-as-you-earn deductions don't take into account any allowances or tax you've already paid earlier in the tax year. Other emergency codes include BR, which taxes all your income at 20%, and 0T, which removes your personal allowance entirely.

How Emergency Tax Is Calculated

Under normal PAYE (cumulative basis), your employer looks at your total earnings and tax paid from April to the current month. This means if you had low earnings earlier in the year, your tax is reduced in later months to use up your unused personal allowance.

On a W1/M1 emergency code, each month is treated in isolation. You receive one twelfth of the annual personal allowance (£1,047.50 per month) and the standard tax bands are applied to that month's pay only. For most people, this results in slightly higher tax because the cumulative smoothing effect is lost.

On a BR code, every penny of your gross pay is taxed at 20% with no personal allowance at all. This happens when HMRC believes you are using your personal allowance elsewhere, for example on a second job. It causes significant overpayment if it's your only income source.

On a 0T code, you get no personal allowance and the progressive tax bands are applied from the first pound. This is the most punitive emergency code and is sometimes used when HMRC cannot determine your correct allowance.

How To Get Your Emergency Tax Refund

The good news is that emergency tax overpayments are almost always refunded. There are several ways to get your money back:

• Automatic correction: Once HMRC issues your correct tax code to your employer, your next payslip should include a refund of the overpaid amount. Under cumulative PAYE, the system automatically catches up.
• Contact HMRC: If your code hasn't been corrected within a few weeks, call HMRC on 0300 200 3300 or use your Personal Tax Account online to check and update your tax code.
• Provide your P45: Give your new employer your P45 from your previous job as soon as possible. This contains the information they need to apply the correct code.
• Complete a P50: If you've stopped working during the tax year and are owed a refund, you can submit form P50 to HMRC to claim it early rather than waiting until the end of the year.

Most refunds come through automatically within 4 to 8 weeks of your tax code being corrected. If you're owed a refund at the end of the tax year, HMRC will typically issue it after processing your P60.

How To Avoid Emergency Tax

The easiest way to avoid being put on an emergency tax code is to give your new employer your P45 on your first day. If you don't have a P45 — for example, it's your first ever job or you've been self-employed — complete a starter checklist (formerly P46) so your employer can set up the correct code from the start.

You can also check your tax code proactively using your HMRC Personal Tax Account. If you spot an incorrect code, you can request a correction online. Using the UK Take Home Pay calculator to compare your expected take-home pay with your actual payslip is a quick way to spot if something is wrong.

For more on how tax codes work and what each letter means, read our complete guide to UK tax codes.