Emergency Tax Codes: What They Mean and How to Fix Them
An emergency tax code is a temporary tax code applied by HMRC or your employer when they do not have enough information to calculate your correct tax. It usually results in overpaying tax — sometimes significantly. Knowing what each code means and how to fix it quickly can save you hundreds of pounds.
What Is a Tax Code?
Your tax code tells your employer how much of your income is tax-free and which rate to apply. The standard code for 2025/26 is 1257L, representing the £12,570 Personal Allowance. Emergency codes are used when your employer does not yet have your full tax details.
Common Emergency Tax Codes and What They Mean
| Code | What it means | Effect on your pay |
|---|---|---|
| BR | Basic rate — no Personal Allowance | 20% tax on all earnings |
| D0 | Higher rate — no Personal Allowance | 40% tax on all earnings |
| D1 | Additional rate — no Personal Allowance | 45% tax on all earnings |
| 0T | Zero allowance — cumulative or non-cumulative | 20%, 40% or 45% depending on earnings, no allowance |
| 1257L W1 | Week 1 basis — non-cumulative | Personal Allowance applied per week only |
| 1257L M1 | Month 1 basis — non-cumulative | Personal Allowance applied per month only |
Why Are Emergency Codes Issued?
- Starting a new job: your employer has not yet received a P45 or details from HMRC
- Starting a second job: HMRC assumes no allowance is available for additional employment
- Returning to work after a long gap: records may be out of date
- Pension withdrawals: first withdrawal from a pension often triggers an emergency code
- HMRC systems not updated: for example after a move, name change or new tax return
Pension withdrawals are a particularly common trigger. The first flexible drawdown payment from a pension is almost always taxed on an emergency basis (Month 1 code), which can mean paying far too much tax on a large sum. You usually need to claim a refund via form P55, P50Z or P53Z.
W1/M1: Non-Cumulative Codes Explained
Normally, income tax is calculated cumulatively across the tax year — your employer considers all the income and tax you have paid since April and adjusts each payslip accordingly. A W1 (Week 1) or M1 (Month 1) code removes this cumulative calculation. Each pay period is treated independently, as if it were the first of the year. This can result in overpayment if you had a low-income period earlier in the year.
How to Fix an Emergency Tax Code
- Provide your P45: give your new employer your P45 from your previous job as soon as possible
- Complete a Starter Checklist: if you do not have a P45, your employer should give you a Starter Checklist (formerly P46) — answer the questions carefully as they determine your initial code
- Contact HMRC directly: call 0300 200 3300 or update your details via your Personal Tax Account at gov.uk/check-income-tax-current-year
- Wait for HMRC to correct it: HMRC will usually update your code automatically once they process the relevant information — your employer will receive a new code and adjust your next payment
Getting a Refund of Overpaid Tax
If an emergency code was used for part of the year, the easiest way to get your refund is through payroll — once HMRC issues the correct code, your employer's payroll software should automatically calculate any underpayment or overpayment and adjust future payments accordingly. If you have left the job or it is after the tax year end, you will need to claim directly from HMRC.
You can check and update your tax code any time through your HMRC Personal Tax Account at gov.uk. You can also see historic tax codes and immediately flag errors without needing to call.
Frequently Asked Questions
Frequently Asked Questions
Marcel Tonet
AAT Qualified · CeMAP Qualified · Tech & Financial Services
Marcel is an AAT-qualified accounting technician and CeMAP-qualified mortgage adviser with a career spanning technology and the UK financial services industry. He built and maintains Salary Take Home UK, updating all tax rates and thresholds each April for the new tax year.
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