Emergency Tax Calculator
Updated November 2026 · Free · No sign-up
Calculate how much emergency tax you're paying — what a W1/M1 or 0T code deducts versus your correct tax, the refund building up, and how to end it fast.
Quick answer: Emergency codes tax each payday in isolation (1257L W1/M1) or with no allowance at all (0T/BR). On a £3,000 monthly salary, 0T deducts ~£594 vs the correct ~£384 — ~£210/month overpaid until HMRC issues your cumulative code, then payroll refunds automatically.
What Emergency Tax Actually Is
When payroll lacks your history (new job without P45, first job, pension start, big benefit changes), HMRC applies a holding code:
- 1257L W1/M1: the normal allowance but non-cumulative — each period gets 1/12 (or 1/52) of the allowance with no year-to-date catch-up. Usually close to correct for steady pay; wrong when you had a gap or uneven income.
- 0T: zero allowance, banded rates — overtaxes almost everyone.
- BR: flat 20% — overtaxes main jobs, undertaxes higher-rate earners (a nasty later bill).
Worked Examples
Example 1 — 0T on £3,000/month. Correct (1257L cumulative): ~£384. 0T: ~£594. Overpaying ~£210/month; three months = £630 queued for refund.
Example 2 — W1 after a work gap. Unemployed Apr-Aug, started in Sep at £3,000/mo: W1 taxes each month alone, ignoring 5 months of unused allowance — cumulative code triggers a ~£1,000+ refund in one payslip.
Example 3 — BR for a higher earner. £6,000/month on BR pays 20% flat = £1,200 vs correct ~£1,453 — an underpayment accruing toward a year-end demand. Emergency tax isn't always overpayment; check your direction.
Ending It (Days, Not Months)
| Step | Action |
|---|---|
| 1 | Give your new employer the P45 — or complete the starter checklist accurately (statement A/B/C decides the first code) |
| 2 | Check/update income estimates in the HMRC app — new codes typically issue within days |
| 3 | Once a cumulative code lands, payroll auto-refunds in the next run — no claim needed in-year |
| 4 | Left it past 5 April? P800 reconciliation or an R38/online claim recovers prior-year overpayments (4-year window) |
Pension Withdrawals: The Emergency-Tax Trap
First flexible pension withdrawals are taxed on an emergency month-1 basis — a £20,000 taxable withdrawal gets treated as £240,000/year income, withholding thousands too much. Reclaim in-month with forms P55/P53Z/P50Z instead of waiting for year-end — HMRC repays within ~30 days. Retirees tapping pots for the first time hit this constantly.
Reading the Damage on Your Payslip
Identify the code (top of payslip) and the basis — "W1", "M1", or "X" after it means non-cumulative. Compare the period's tax against this calculator's correct-code figure; multiply the gap by periods elapsed for your queued refund. Then decode the destination code with the tax code checker so the fix lands right the first time.
Frequently Asked Questions
How much is emergency tax?
Depends on the code: 0T taxes everything at banded rates with no allowance (~£210/month extra on £3,000); BR takes flat 20%; 1257L W1/M1 is near-correct for steady pay but ignores gaps.
How do I stop paying emergency tax?
P45 to your employer or an accurate starter checklist, plus updated estimates in the HMRC app — cumulative codes issue in days and payroll refunds automatically.
When will I get my emergency tax refund?
In-year: the first payslip after your cumulative code arrives. After year-end: via P800 or a claim, up to four years back.
Why was my pension withdrawal taxed so heavily?
First withdrawals use an emergency month-1 basis that annualizes the lump sum — reclaim immediately with P55/P53Z/P50Z rather than waiting until April.
Can emergency tax UNDERCHARGE me?
Yes — BR on higher-rate income withholds only 20%, building a year-end liability. Check direction, not just presence, of the error.
What is the starter checklist?
The P45-replacement declaration (statements A/B/C) that sets your first code — answering it accurately is the difference between 1257L and months of 0T.
✓ Formula verified • Last updated: November 3, 2026