Ever opened your payslip and noticed way more tax taken off than you expected? If your tax code has “W1”, “M1”, or “X” after it, you’re likely on Emergency Tax Explained. It’s more common than people realise — especially when starting a new job, switching from self-employment, or picking up a second income.
The good news: emergency tax is usually temporary, and if you’ve overpaid, you can claim it back. Emergency Tax UK This guide walks you through what emergency tax actually is, why it happens, and exactly how to get your money back.
What Is Emergency Tax?
Emergency tax is a temporary tax code HMRC applies when they don’t yet have enough information about your income to calculate your tax correctly. Emergency Tax UK Instead of using your full year’s earnings to work out your Personal Allowance, your employer taxes you based only on that single pay period — often assuming you have no tax-free allowance at all.
This usually results in you paying more tax than you should, at least until HMRC receives your full details and issues a correct tax code.
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Why Does Emergency Tax Happen?
There are a handful of common situations that trigger it:
- You started a new job without a P45 from your previous employer
- You moved from self-employment to employment
- You started receiving a new pension alongside other income
- You began a second job while still working your main one
- HMRC didn’t have your details updated in time for your first payday
- You returned to work after a period of unemployment or benefits
In all of these cases, your employer doesn’t have the full picture of your income history for the tax year, so they apply a temporary code as a safety measure.
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Emergency tax codes usually look like your standard tax code, but with an extra marker attached. The most common ones are:
| Emergency Code | What It Means |
|---|---|
| 1257 W1 | Calculated weekly, based only on that week’s pay |
| 1257 M1 | Calculated monthly, based only on that month’s pay |
| 1257 X | Non-cumulative code, similar effect to W1/M1 |
| BR | Basic rate (20%) applied to all income, no tax-free allowance |
| 0T | No tax-free allowance at all |
The “W1” and “M1” tags mean your tax is worked out fresh each pay period, rather than looking at your total earnings across the year. Emergency Tax UK This is what usually leads to overpayment, since it ignores unused tax-free allowance from earlier months.
Example: How Emergency Tax Affects Your Pay
Let’s say you start a new job in July without a P45, and you’re placed on a 1257 M1 emergency code.
| Scenario | Normal Tax Code | Emergency Tax Code (M1) |
|---|---|---|
| Monthly salary | £2,500 | £2,500 |
| Tax-free allowance applied | Full year’s allowance spread across months | Only that month’s allowance |
| Tax deducted | Based on cumulative earnings | Based only on this month, ignoring earlier unused allowance |
| Result | Correct tax | Often overpaid |
If you’d already been unemployed for part of the year, a normal tax code would account for those unused tax-free months. Emergency Tax UK An emergency code doesn’t — so you end up taxed as if you’d been earning that amount every month all year.
How Much Extra Could You Pay?
It depends on your income and how long you’re on the emergency code, but it’s not unusual for people to overpay several hundred pounds in a single month, particularly if:
- You started work partway through the tax year
- You had a gap in employment beforehand
- Your new employer doesn’t have your previous earnings on record
The longer it takes HMRC to issue your correct code, the more you could overpay — which is exactly why it’s worth sorting out quickly rather than waiting for it to fix itself Emergency Tax UK.
Step-by-Step: What to Do If You’re on Emergency Tax
Step 1: Check Your Payslip
Look for your tax code next to your National Insurance number. If it ends in W1, M1, or X, or shows BR/0T unexpectedly, you’re likely on an emergency code.
Step 2: Give Your Employer a P45 (If You Have One)
If you left a previous job recently, hand your P45 to your new employer as soon as possible. Emergency Tax UK This gives them your income and tax details for the year, allowing them to apply the correct code without needing HMRC to step in Emergency Tax UK.
Step 3: Complete a Starter Checklist (If You Don’t Have a P45)
If you don’t have a P45 — maybe you’re starting your first job, or came from self-employment — ask your employer for a Starter Checklist. This form asks about your employment history and helps assign a more accurate code from the start.
Step 4: Contact HMRC Directly
If your emergency code hasn’t been corrected after your first payday, or you think you’re being taxed incorrectly, contact HMRC through:
- Your personal tax account on GOV.UK
- The HMRC helpline
- Webchat support on the HMRC website
Have your National Insurance number, employer details, and recent payslips ready Emergency Tax UK.
Step 5: Wait for Your Tax Code to Update
Once HMRC has the correct information, they’ll issue an updated PAYE Coding Notice, and your employer will apply it going forward.
Step 6: Check for a Refund
Emergency tax often corrects itself automatically. Emergency Tax UK Once your proper tax code is applied, your employer will usually refund any overpaid tax through your payslip — either as a lump sum adjustment or spread across future pay periods Emergency Tax UK.
How to Claim Back Emergency Tax
Emergency Tax UKIf your tax code isn’t automatically corrected, or the tax year has already ended before you notice the overpayment, here’s how to claim it back:
- Log into your HMRC personal tax account and check your Income Tax summary for the year Emergency Tax UK.
- Compare what you’ve paid against what you should have paid, based on your correct tax code Emergency Tax UK.
- Submit a claim through GOV.UK if HMRC confirms you’ve overpaid — this can often be done online.
- Wait for your refund, which HMRC usually issues either as a bank transfer or a cheque Emergency Tax UK.
- Check again the following year if you’re unsure — HMRC also runs automatic end-of-year reconciliations and may issue a refund without you needing to ask Emergency Tax UK.
If the tax year has ended and you never claimed, you can usually go back and claim overpaid tax for up to four previous tax years.
Emergency Tax on Pensions
Emergency tax doesn’t just apply to employment — it’s also common when you first access a pension, particularly if you take a lump sum. Emergency Tax UK Pension providers often apply emergency tax to the first payment because they don’t yet know your full tax position for the year.
This can result in a much larger deduction than expected on that first pension withdrawal. Emergency Tax UK The process to reclaim it is similar: check your tax code, contact HMRC or your pension provider, and claim back any overpayment using the relevant HMRC form for pension tax refunds.
How Long Does It Take to Fix Emergency Tax?
In most cases, once your employer has your correct details (through a P45 or Starter Checklist), your tax code updates within one to two pay periods. If HMRC needs to step in directly, it can take a little longer — often a few weeks — depending on how quickly they process your case.
How to Avoid Emergency Tax in the Future
A few simple habits can help you avoid it altogether:
- Always give your new employer your P45 as soon as you get it
- Fill in the Starter Checklist accurately if you don’t have a P45
- Keep an eye on your first two or three payslips in any new job
- Update HMRC promptly if your circumstances change (new pension, second job, etc.)
- Check your personal tax account periodically, even outside of job changes
FAQ’s
What does emergency tax mean?
It means your employer or pension provider is temporarily taxing you without full information about your income, usually resulting in you paying more tax than necessary until HMRC issues your correct tax code.
How do I know if I’m on emergency tax?
Check your payslip for a tax code ending in W1, M1, or X, or an unexpected BR or 0T code.
Will emergency tax correct itself?
Often, yes. Once your employer receives your P45 or HMRC updates your tax code, your pay usually adjusts automatically, and any overpaid tax is refunded through your payslip.
How long does emergency tax last?
It typically lasts one to two pay periods once your correct details are provided, though it can take longer if HMRC needs to intervene directly.
Can I claim emergency tax back myself?
Yes. You can check your tax record through your HMRC personal tax account and submit a claim online if you’ve overpaid.
How far back can I claim overpaid tax?
You can usually claim back overpaid tax for up to four previous tax years.
Does emergency tax apply to pensions too?
Yes, especially on the first pension withdrawal, since providers often don’t have your full tax details at that point.
What’s the difference between BR and emergency tax codes like M1?
BR taxes all your income at the basic rate with no tax-free allowance, while M1/W1 codes calculate tax based only on that single pay period rather than your full year’s earnings.
Do I need to do anything if my new employer already has my P45?
Usually not — if your P45 is submitted promptly, your employer can often apply the correct tax code straight away, avoiding emergency tax altogether.
Can emergency tax affect my Self Assessment if I’m also self-employed?
It can affect how much tax you’ve already paid through PAYE, which is factored into your overall Self Assessment calculation, so it’s worth checking both together.