Emergency Tax Code 2026/27: Why New Employees Get Taxed Wrong (and How to Fix It)
Started a new job without a P45? You've probably been put on an emergency tax code, which can mean overpaying tax for weeks or months until it's corrected. Here's how emergency codes work and how to get any overpayment back quickly.
Why Emergency Codes Exist
When you start a new job, your employer needs accurate information about your tax position — including how much you've already earned and been taxed this tax year — to apply the correct tax code. If that information isn't available (most commonly because you haven't provided a P45 from your previous employer, or a new starter checklist hasn't been completed accurately), HMRC's default fallback is an emergency tax code.
For 2026/27, the standard emergency code is:
1257L W1 (or 1257L M1) — meaning the standard £12,570 Personal Allowance, applied on a Week 1 or Month 1 (non-cumulative) basis depending on your pay frequency.
Cumulative vs Non-Cumulative: The Key Difference
| Basis | How it works |
|---|---|
| Cumulative (normal) | Total pay and tax to date in the tax year are tracked; Personal Allowance is applied proportionally across the whole year so far, self-correcting as the year progresses |
| Non-cumulative (emergency, W1/M1) | Each pay period treated in isolation — as if it's the only pay period in the entire tax year, ignoring any earlier pay or tax (from this job or elsewhere) |
Why this matters: under a cumulative code, if you were unemployed for the first three months of the tax year and then start a job in month four, your tax calculation accounts for the fact that you haven't used any of your Personal Allowance yet — resulting in less tax deducted initially to "catch up." Under a non-cumulative emergency code, this catch-up doesn't happen — each pay period gets only that period's proportional slice of the allowance, regardless of unused allowance from earlier months, typically resulting in more tax being deducted than is actually owed for the year as a whole.
Worked Example
Sam is unemployed from April to July, then starts a new job in August (month 5 of the tax year) without a P45, going onto an emergency 1257L M1 code, earning £2,500/month.
| Scenario | Personal Allowance applied to August's pay | Tax on £2,500 |
|---|---|---|
| Cumulative code (correct) | 5/12 of £12,570 = £5,238 applied cumulatively, using unused allowance from April-July | Little or no tax due in August, catching up unused allowance |
| Emergency M1 code (non-cumulative) | Only 1/12 of £12,570 = £1,048 applied to this single month | Tax due on £2,500 − £1,048 = £1,452 at 20% = £290.40 |
Sam is likely significantly overtaxed in August under the emergency code, compared to what a correct cumulative calculation — accounting for the unused allowance from the unemployed months — would produce.
How to Get Off the Emergency Code Quickly
| Action | Effect |
|---|---|
| Provide your P45 from your previous employer | Gives your new employer your tax code and pay/tax-to-date figures, usually allowing a correct cumulative code from the next payslip |
| Complete a new starter checklist accurately (if no P45 available) | Lets your employer apply a more appropriate code based on your declared circumstances (e.g., "this is my only job," "I have another job or pension") |
| Contact HMRC directly if the emergency code persists | HMRC can issue an updated tax code directly to your employer if the automatic process hasn't resolved things |
The starter checklist specifically asks whether this is your only job, whether you've had other taxable income this tax year, and whether you're repaying a student loan — answering accurately is important, since an inaccurate answer can result in an incorrect (rather than simply temporary emergency) code being applied.
Getting a Refund If You've Overpaid
| Situation | How the refund happens |
|---|---|
| Correct cumulative code applied later in the same tax year | Often automatic — the payroll system recalculates cumulatively and refunds the overpaid amount through a subsequent payslip |
| Tax year ends before the correction is fully caught up | HMRC typically issues a P800 tax calculation after the tax year ends, confirming any refund due, which can usually be claimed online or is sometimes paid automatically |
| No automatic correction has happened | You can contact HMRC directly (via your personal tax account or by phone) to query and request a review of the position |
Don't assume an emergency-code overpayment will always sort itself out with no action needed — while it often does correct automatically within the same tax year once your correct code is applied, it's worth checking your payslips and, if needed, proactively contacting HMRC, particularly if you've changed jobs more than once in a tax year or your circumstances are otherwise unusual.
When Emergency Codes Cause Underpayment Instead
Less commonly, an emergency code can result in underpaying tax — for example, if you have more than one job and the emergency code on a new job applies a full Personal Allowance that should, in reality, be allocated (or already fully used) elsewhere. This can create an unexpected tax bill later, typically collected via an adjustment to a future tax code rather than requiring an immediate lump sum payment, but worth being aware of if your circumstances involve multiple income sources.
Checking your tax code on every new payslip — particularly in the months after starting a new job — is the simplest way to catch an incorrect emergency code early, before it compounds into either a larger overpayment or underpayment.
Frequently asked questions
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