Emergency Tax Calculator 2026/27: What That Code Is Costing You

Work out your emergency tax above

Pop in your gross pay for the period and the emergency code shown on your payslip, and the calculator above does the rest. It compares the tax taken under the emergency code with the tax you'd normally pay on a standard code, so you can see the gap at a glance. Read on for how the maths works, a full worked example, and exactly how to get any overpaid tax back.

What emergency tax actually is

Emergency tax is not a separate, higher rate of tax. It is a temporary tax code your employer or pension provider uses when HMRC hasn't yet given them the right details to work out your allowances. Because the system plays it safe, it often takes more tax than you actually owe, which is why people search for an emergency tax calculator after a shock payslip.

You typically end up on an emergency code when you start a new job without a P45, take a second job, move from self-employment into employment, or start drawing a private or workplace pension. Until HMRC sends your employer the correct code, the payroll software defaults to an emergency one.

The most common emergency codes you'll see on a 2026/27 payslip are 1257L W1, 1257L M1 and 0T. The "1257L" part still gives you the standard tax-free Personal Allowance of £12,570 for the year. It is the small letters after it that change how the tax is worked out. For what each code letter means in detail, our tax code calculator breaks down the numbers and suffixes.

Emergency tax codes explained: W1, M1 and 0T

The behaviour of an emergency code depends on which version you're on.

• 1257L W1 (week 1) or M1 (month 1): You still get the full £12,570 Personal Allowance, but it is applied on a non-cumulative basis. Instead of spreading your allowance and tax bands across the whole year so far, payroll treats every pay period as if it were the first of the tax year. You get 1/52 of your allowance each week, or 1/12 each month, with no catch-up for earlier periods.
• 0T: This is the harsher one. The 0T code gives you no Personal Allowance at all and taxes every pound from the first, applying the 20%, 40% and 45% bands as your pay rises. It is usually used when you've given no starter details to a new employer, or on certain pension payments.

A cumulative code (the normal kind, with no W1/M1) looks at your total pay and total allowance for the year to date, so it self-corrects. An emergency code can't do that, which is how overpayments build up.

How the emergency tax calculator works

The calculator uses the same logic HMRC's payroll software does, just made visible. In plain words:

Emergency tax (W1/M1) = (Pay for the period − period's slice of Personal Allowance) taxed through the bands, with no year-to-date adjustment.

Emergency tax (0T) = the whole pay for the period taxed through the bands, with no Personal Allowance at all.

For 2026/27 the figures that feed the maths come straight from gov.uk. The Personal Allowance is £12,570, which is £1,048 a month or £242 a week. The 20% basic rate covers the first £37,700 of taxable income, the 40% higher rate runs from £37,700 to £125,140, and the 45% additional rate applies above that. On a W1/M1 monthly code, payroll uses 1/12 of each band; on a weekly code, 1/52.

The calculator then works out what you would have paid on a normal cumulative 1257L code and shows the difference. That difference is, in most cases, the amount you've overpaid and can reclaim. National Insurance is calculated per pay period regardless of your tax code, so an emergency code doesn't usually change your NI, only your income tax.

Worked example: how much emergency tax will I pay?

Let's take a relatable case. Priya leaves one job and starts a new one in May 2026 on a salary of £36,000 a year, or £3,000 a month. She doesn't hand over a P45 in time, so her first payslip is taxed on 0T.

Under the 0T emergency code (no Personal Allowance):

• Monthly pay: £3,000
• One-twelfth of the £37,700 basic-rate band = £3,141.67, so all £3,000 sits in the basic band
• Income tax: £3,000 × 20% = £600

Under a normal 1257L code:

• Monthly tax-free allowance: £1,048
• Taxable pay: £3,000 − £1,048 = £1,952
• Income tax: £1,952 × 20% = £390.40

So in that single month Priya pays about £209.60 more than she should because of the emergency code. Over three months on 0T before HMRC fixes her code, that's roughly £628 of overpaid tax tied up unnecessarily.

Now a second example on a W1/M1 code. Tom starts a job paying £4,500 a month and is put on 1257L M1. He still gets £1,048 of allowance each month, so his taxable pay is £3,452. The first £3,141.67 is taxed at 20% (£628.33) and the remaining £310.33 at 40% (£124.13), giving about £752 of tax that month. The sting here isn't a missing allowance; it's that the code can't carry forward any unused allowance or lower-rate band from earlier weeks when he wasn't working, so he may still be slightly overtaxed until the code goes cumulative.

For a fuller picture of your annual position, run the figures through our income tax calculator or check your overall take-home with the salary calculator.

2026/27 income tax rates and thresholds

These are the figures the emergency tax calculator applies for England, Wales and Northern Ireland. Scotland sets its own rates and bands (see below).

The Personal Allowance is reduced by £1 for every £2 of income over £100,000, and disappears entirely at £125,140. Source: gov.uk emergency tax codes, checked for the 2026/27 tax year.

Scotland: a different set of bands

If you live in Scotland your tax code usually starts with an S (for example S1257L), and Scottish income tax rates and bands apply to your earnings rather than the rest-of-UK ones above. The £12,570 Personal Allowance is the same UK-wide, but the rates above it differ, with more bands and a top rate higher than 45%. An emergency Scottish code behaves the same way (W1/M1 or S0T), it just runs your pay through the Scottish bands. If your payslip code begins with S, use our Scotland tax calculator for figures that match your bands.

How to get emergency tax refunded

The good news is that emergency tax almost always corrects itself, and you rarely have to fight for the money. Here's what actually happens and what you can do to speed it up.

• Give your new employer a P45 or complete the starter checklist. Your P45 from your last job tells the new payroll your code and pay to date. No P45? Fill in HMRC's starter checklist (your employer provides it) so the right details reach HMRC quickly.
• Wait for the code to update. Once HMRC has your details, it issues a correct cumulative code to your employer. If you're still mid-tax-year, the next payslip usually repays the overpaid tax automatically through your wages, so you may see a larger-than-normal pay packet.
• Check your code on your Personal Tax Account. Log in at gov.uk to see your current code and tell HMRC if anything looks wrong, such as a missing allowance or the wrong employer listed.
• If the year has ended and you're still owed money, HMRC reconciles it after 5 April and sends a P800 calculation, then a refund. You don't always need to claim, but you can chase it.

If you think you've overpaid across a whole tax year, our tax refund calculator helps you estimate what HMRC might owe you before you contact them.

Common mistakes and what to watch

• Assuming emergency tax is lost forever. It isn't. An emergency code overtaxes you temporarily; once your correct code lands, the system pays you back, either through your wages or via a P800 after year end.
• Confusing 0T with BR. A BR code taxes all your income at 20% and is normally used for a second job, not an emergency. 0T uses the full band structure (20%/40%/45%) but with no allowance. They are not the same, and mixing them up changes your estimate.
• Forgetting the second-job effect. If your emergency code appears on a second job, remember your Personal Allowance is usually already used by your main job. Our second job tax calculator shows how the allowance is split.
• Not handing over a P45 promptly. The single biggest cause of dragged-out emergency tax is missing starter details. Completing the starter checklist on day one is the fastest fix.
• Pension drawdown shock. Taking a one-off pension lump sum often triggers an emergency code, and the tax taken can look enormous because payroll treats it as if you'll receive that amount every month. This usually corrects later, but it catches a lot of people out.

These estimates are for guidance only and are not personal tax or financial advice; check your own code and figures with HMRC or a qualified adviser before acting.

Related calculators

Once you've sized up the emergency tax, it helps to see your wider position. Decode the letters and numbers on your payslip with the tax code calculator, work out your full annual bill with the income tax calculator, and check what's actually owed back to you using the tax refund calculator.

You might also need

• Tax Code Checker, see whether your emergency code has updated.
• check what you are owed, emergency codes often lead to a refund.

Related tools

• HMRC letter decoder, understand an HMRC letter.

Related guides

Emergency tax usually starts with a missing P45: read what a P45 is and what tax code 1257L means.