What is an emergency tax code?

An emergency tax code (1257L W1, 1257L M1, or X) means tax is calculated non-cumulatively — each pay period is treated in isolation. This often results in overpaying tax, especially if you start a job mid-year, because unused Personal Allowance from earlier months is not carried forward.

How long does emergency tax last?

Emergency tax is temporary. Once your employer receives your P45 and HMRC issues a cumulative code, deductions correct automatically — usually within 1–3 payroll runs. Any overpaid tax is refunded through your next payslip once the cumulative code is active.

How do I get off emergency tax?

Give your employer your P45 immediately when starting a new job. If you don't have one, complete a Starter Checklist. HMRC will issue a cumulative code to your employer. You can also contact HMRC directly on 0300 200 3300 to request a code update.

Emergency Tax Code Explained | W1, M1 & BR

An emergency tax code means your employer is calculating tax non-cumulatively — treating each pay period in isolation rather than accounting for the whole year — which often results in overpaying tax temporarily. Emergency codes always carry a suffix: W1, M1 or X.

What Emergency Tax Codes Look Like

CodeWhat It MeansRisk

1257L W1Weekly, non-cumulative — each week treated independentlyOverpayment likely

1257L M1Monthly, non-cumulative — each month treated independentlyOverpayment likely

BR20% flat on all income, no allowance — common for second jobsHigh overpayment on main job

0TNo allowance, progressive rates — used when HMRC has no dataCan be worse than BR

Why Are You Put on Emergency Tax?

Starting a new job without a P45 — your new employer has no tax history
First ever job — no prior employment record in HMRC's system
Returning to work after a gap — outdated HMRC records
Second job — code BR is applied to prevent double Personal Allowance
HMRC processing delay — even with all correct information, it can take 1–2 payroll runs

How to Fix It Fast

Give your employer your P45 from your previous job — this is the fastest fix. They pass it to HMRC who issues a cumulative code. If you don't have a P45 (new to work, self-employment, gap), complete a Starter Checklist (formerly P46) with your employer.

Once HMRC issues a cumulative code, your employer's payroll will automatically recalculate your year-to-date position and refund any overpayment through your next payslip.

Already left the job? HMRC reconciles your tax position after 5 April and issues a P800 refund notice. You can also contact HMRC directly on 0300 200 3300 to request an in-year refund check.

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Emergency Tax Code Explained — W1, M1 & BR

What Emergency Tax Codes Look Like

Why Are You Put on Emergency Tax?

How to Fix It Fast

Calculate your take-home pay