What is the emergency tax code for 2025/26?

The standard emergency code is 1257L W1, 1257L M1, or 1257L X — applied non-cumulatively. It gives the £12,570 Personal Allowance but on a per-period basis only, ignoring year-to-date earnings.

Will I always get a refund from emergency tax?

Not always. If you've earned consistently, the emergency and cumulative calculations may produce nearly identical figures. Refunds are most common when you've had a low-income or unemployed period earlier in the tax year, leaving unused allowance the cumulative code 'gives back'.

How long does emergency tax last?

Until HMRC issues the cumulative code. Typically 4–8 weeks. You can speed it up by ensuring your employer has your P45 or completed starter checklist.

Can I claim back emergency tax myself?

Yes — if the cumulative code doesn't arrive within the tax year, you can claim a refund through self-assessment or by phoning HMRC. After year-end, HMRC issues a P800 letter reconciling automatically.

Does emergency tax apply to NI as well?

NI is calculated each pay period on the actual earnings, so NI is largely unaffected by the emergency code. The issue is income tax only.

Why is BR worse than 1257L M1?

BR (basic rate) gives no Personal Allowance — every pound is taxed at 20%. 1257L M1 gives the full £1,047.50 monthly allowance. On a £35k salary, BR results in roughly £2,500 more annual tax than 1257L M1.

What if my new employer doesn't have my NI number?

They should still process you under emergency code using the starter checklist. Provide NI number ASAP — found on payslips, P60, or HMRC letters.

Should I worry about emergency tax for a temporary contract?

Short-term contracts often end before HMRC issues the cumulative code, leaving you on emergency tax for the whole period. After year-end, the P800 reconciliation refunds any overpayment. Keep all payslips.

Emergency Tax Code 1257L M1/W1 Calculator UK 2025/26

How emergency tax codes work in 2025/26

An emergency tax code is HMRC's default when an employer doesn't have enough information to apply the correct cumulative code. The most common emergency code in 2025/26 is 1257L W1/M1/X — giving the standard Personal Allowance, but applied non-cumulatively. The "W1" means weekly basis, "M1" means monthly basis, and "X" is generic.

The non-cumulative trap: A cumulative code looks at year-to-date earnings and year-to-date allowance, so if you earn nothing for the first 6 months and then start a job in October, you get 6 months of unused allowance refunded in your first payslip. A non-cumulative (W1/M1) code only gives you that period's allowance — you may overpay tax at the start of a job and reclaim later.

Common scenarios for emergency codes:

Starting a new job without giving the employer your P45.
Filling in the starter checklist Statement A/B/C unfavourably.
Returning to work after a long absence.
Receiving income from a new pension provider.
HMRC system errors during the transition between jobs.

Reclaiming overpaid emergency tax

If you've been on an emergency code and overpaid tax, the easiest path to a refund is:

Submit your starter checklist promptly. If you have your P45, give it to your new employer immediately.
Complete the starter checklist (formerly P46). Tick Statement A (this is your only/main job) for the most favourable treatment.
Wait for HMRC to issue the cumulative code. Usually 4–8 weeks. Once issued, your next payslip should refund the overpayment automatically (showing as negative tax / refund).
Check via Personal Tax Account. Log in to gov.uk to see the code in real time.
Contact HMRC if needed. Phone 0300 200 3300 if delays exceed 2 months. They can manually issue the cumulative code.

If the tax year ends with you still on an emergency code, HMRC will reconcile through a P800 calculation letter (around July to September following year-end) and refund any overpayment. You can also file a self-assessment return to expedite a refund.

Three worked examples (UK 2025/26)

Example 1: Mid-year £35k job on 1257L M1

Tariq starts a £35,000 job in October (month 7). He doesn't have a P45 because he was unemployed for 6 months.

Calculation under 1257L M1: Monthly gross £2,917. Allowance £1,047.50. Taxable £1,869.50 × 20% = £373.90/month income tax. NI also applied. Over 6 remaining months: £2,243 tax + NI.

Calculation under cumulative 1257L: When HMRC issues cumulative code, Tariq's full year-to-date allowance is £12,570 (since he earned nothing April–September). Year-to-date earnings £2,917 × 1 month = £2,917. Tax due £0 (within allowance). Refund of £374 in next payslip. Once switched, future months continue cumulative.

Example 2: P45 supplied, no emergency code

Sarah hands her P45 (showing year-to-date pay £18,000, tax £1,086 from prior employer) to her new employer. New employer uses 1257L cumulative from day one.

Outcome: No emergency tax. PAYE calculations use cumulative figures correctly from the start.

Example 3: Emergency on £80k role — overpayment risk

Diego starts an £80,000 role mid-year on 1257L M1.

Each month under M1: Gross £6,667 − £1,047.50 = £5,619.50 taxable. £3,141.67 (basic, 1/12 of £37,700) at 20% = £628.33 + remainder at 40%. He's overtaxed because the M1 code doesn't recognise that earlier in the year his income was zero. When the cumulative code switches, he could get a £2,000+ refund in one month.

Common mistakes to avoid

Failing to give new employer the P45 — straight into emergency tax.
Ticking Statement C ('have another job') when you don't — gets BR code (worst case).
Believing emergency tax is permanent — it self-corrects once HMRC issues the cumulative code.
Not registering for HMRC Personal Tax Account — main tool to check and update codes.
Waiting until year-end to chase a refund — call HMRC at month 2-3 to expedite.
Confusing emergency code with BR code — BR is far worse (no allowance at all).

When to use this calculator

Run this calculator any time you start a new job, switch from self-employment to employment mid-year, or notice an unusually low first-month take-home. Compare what you'd pay on cumulative 1257L vs emergency 1257L M1 to estimate the eventual refund. Check your code in HMRC's Personal Tax Account at gov.uk and contact HMRC if it doesn't auto-update within 4-6 weeks.

Regional differences (Scotland, Wales, Northern Ireland)

Tax codes are issued by HMRC and apply to UK-wide employees. Scotland uses tax codes prefixed "S" (e.g. S1257L) to indicate Scottish income tax bands (Starter 19%, Basic 20%, Intermediate 21%, Higher 42%, Advanced 45%, Top 48%) — the numerical allowance portion is the same as rUK. Wales uses "C" (e.g. C1257L) for Welsh resident, but Welsh rates currently match UK. Northern Ireland uses standard UK codes throughout. The numerical part of the code (e.g. 1257 for £12,570 PA) is identical across the UK; only the prefix changes the band structure.

Emergency Tax Code Calculator — 1257L W1/M1/X — 2025/26

Tax code calculator