In most cases you do not need to actively claim back emergency tax, HMRC corrects it automatically once your employer reports the right details, and any overpayment is refunded through your next payslip or in a P800 tax calculation after the tax year ends. To speed things up, give your new employer your P45 or complete a Starter Checklist, and check your tax code in your Personal Tax Account. If you're owed a refund and no correction appears, you can claim directly through the HMRC tax refund tool.
What Is Emergency Tax?
Emergency tax is what you pay when your employer doesn't have enough information to apply your correct tax code. Instead of spreading your tax-free Personal Allowance evenly across the year, the system taxes you as if you have no allowance carried forward, so you often overpay.
For 2026/27 the standard Personal Allowance is £12,570, and the normal tax code is 1257L. You're on an emergency code if your code shows:
- 1257L W1, week 1 basis
- 1257L M1, month 1 basis
- 1257L X, non-cumulative
The "W1", "M1" or "X" suffix is the giveaway. These codes give you the allowance for the current pay period only, ignoring what you've earned and paid so far in the year. If you've started a new job mid-year, that usually means you pay too much.
When Does Emergency Tax Happen?
You're most likely to be put on an emergency code if you:
- Start a new job without a P45 from your previous employer
- Start your first job and haven't completed a Starter Checklist
- Move from self-employment into employment
- Start receiving company benefits or a workplace pension
- Have more than one job or pension at the same time
How Emergency Tax Causes You to Overpay
Under an emergency code, HMRC treats each pay packet in isolation. If you earn £3,000 in your first month at a new job, the system assumes you'll earn that every month, so it taxes you as though you're heading for £36,000 a year, without crediting unused allowance from earlier months when you weren't earning.
The income tax bands for 2026/27 are:
| Band | Taxable income | Rate |
|---|---|---|
| Personal Allowance | Up to £12,570 | 0% |
| Basic rate | £12,571-£50,270 | 20% |
| Higher rate | £50,271-£125,140 | 40% |
| Additional rate | Over £125,140 | 45% |
The allowance tapers away once income passes £100,000, disappearing entirely at £125,140. Emergency codes ignore this nuance, which is exactly why the figures rarely come out right first time.
Want to see what your take-home should be on the correct code? Run your salary through the Zmartly take-home pay calculator and compare it against your payslip.
How to Claim Back Emergency Tax, Step by Step
1. Hand Over Your P45 (or Complete a Starter Checklist)
This is the single fastest fix. Your P45 from your last employer tells your new payroll team your correct cumulative pay and tax. No P45? Ask for the Starter Checklist instead. Once submitted, HMRC issues your proper tax code and most overpayments are refunded automatically in your next pay run.
2. Check and Update Your Tax Code Online
Log in to your Personal Tax Account to see the code HMRC currently holds. If something looks wrong, a missing allowance, an old job still showing as active, you can correct it there, or call HMRC on the income tax helpline. Updating your records often triggers an in-year refund without any further action.
3. Let the Automatic Refund Reach You
If your code is corrected mid-year, the refund usually appears in your next payslip as a "tax refund" line, and your take-home jumps for that pay period.
If it isn't sorted by the end of the tax year (5 April), HMRC reviews your records and sends a P800 tax calculation showing what you overpaid. Per GOV.UK guidance on tax overpayments, you can then claim your refund online by bank transfer (sent within 5 working days), or wait for a cheque, which arrives within 14 days of the date on your P800 letter.
4. Claim Directly If Nothing Happens
If you've left the job, or no correction comes through, use the HMRC claim a tax refund tool. It walks you to the right form based on your circumstances, for example, a P50 if you've stopped working part-way through the year.
How Long Does an Emergency Tax Refund Take?
- In-year, via payroll: as little as one pay cycle once your code is corrected.
- Via P800 online claim: typically around 5 working days for a bank transfer after you claim.
- Via cheque: within 14 days of the date on your P800 letter.
You have up to four years from the end of the relevant tax year to reclaim overpaid tax, so even older emergency-tax years aren't lost.
Do You Need an Accountant to Claim?
For a straightforward employed refund, usually not, the online tools handle it. But it's worth getting advice if you have multiple income sources, recently switched from self-employment, receive taxable benefits, or your P800 figures don't match what you expected. Mistakes in the other direction (underpayments) can quietly build up too. Our FAQ page covers the common edge cases.
Frequently Asked Questions
Will I always be refunded emergency tax?
If you genuinely overpaid, yes, HMRC reconciles your record either in-year or via a P800. The money isn't lost; it's a question of when.
Can I be on an emergency code and underpay instead?
It's possible, particularly with multiple jobs where allowances overlap. That's why checking your code early matters, an underpayment now means a bill later.
What if I've already left the job?
Use the HMRC refund tool and, if you've stopped working, the P50 process. You don't need to wait for the old employer to do anything.
Stuck on an emergency code, juggling more than one job, or staring at a P800 that doesn't add up? A Zmartly accountant can check your tax position, confirm exactly what you're owed, and make sure you're on the right code going forward. Get in touch with us and we'll take it from here.
