Emergency Tax: 0T and BR Explained (2026/27)

“Why has my first paycheck taken so much tax?” is one of the most common questions new employees ask. The usual culprit: an emergency tax code. It’s not a bug and it’s not a scam — it’s HMRC’s safety mechanism when they don’t yet have enough information to give you a proper tax code. This guide walks through why it happens, exactly how much extra you pay, and how to get back to normal (and recover the overpayment).

What “emergency tax” actually means

HMRC and payroll systems use the term “emergency tax” loosely. In practice it covers three overlapping situations:

1. Non-cumulative suffix codes — 1257L W1, 1257L M1, 1257L X. The code uses the normal Personal Allowance but in a special non-cumulative mode.
2. The 0T code — removes your Personal Allowance entirely but still applies the normal band structure (20% / 40% / 45%).
3. The BR code — everything at 20%, no PA. Sometimes used as a “safer than 0T for first-month starters” variant.

All three have one thing in common: you pay more tax in the short term than you would with the correct settled code, usually 1257L.

Why HMRC applies an emergency code

You just started a job and didn’t give your employer a P45

Most common trigger. Without your previous employer’s P45, the new payroll doesn’t know:

• Your year-to-date pay so far
• Your year-to-date tax paid
• Your confirmed tax code from the previous role

HMRC sends the employer a non-cumulative code (1257L W1 or M1) or, depending on the interpretation of your Starter Checklist, 0T or BR.

You started and didn’t complete the Starter Checklist

Without the checklist the employer MUST default to a safer code. 0T or BR is the typical fallback, yielding the highest near-term tax (and the largest refund later).

Your employment situation changed mid-year

Moving from self-employment to employment, returning from parental leave, coming back from overseas — any of these can leave HMRC playing catch-up. Until they reconcile your year-to-date record you stay on non-cumulative coding.

HMRC is missing your P45 details

Even if you provided a P45, HMRC’s processing pipeline can take 1-2 weeks to match it to your new employer’s submissions. During that window you might be on emergency coding.

Exactly how much extra tax are you paying?

1257L W1 / M1 / X (non-cumulative with full PA)

You get 1/52 of the PA per week (£242) or 1/12 per month (£1,048) in isolation. If your first monthly pay is £3,000 and it’s month 7 of the tax year, cumulative PAYE would spread 7/12 of your £12,570 PA (£7,333) against the 7 months of pay — giving more tax-free room. Non-cumulative applies only the single month’s 1/12, so you pay tax on £3,000 − £1,048 = £1,952 × 20% = £390 that month.

Over a few months this could over-tax you by hundreds until HMRC flips you to cumulative.

0T code (no PA)

Zero Personal Allowance but full band structure.

On a £35,000 annual salary paid monthly (£2,917/month):

• 0T applies no PA — every £ taxable
• Month 1 tax: £2,917 × 20% = £583 (if all below higher-rate monthly threshold)
• Compare to 1257L: (£35,000 − £12,570) / 12 × 20% = £374/month
• Overpayment: £209/month

BR code (20% flat, no PA)

Every pound taxed at 20%, no PA, no band structure above 20%.

For someone who would normally be a basic-rate taxpayer on BR at their only job: over-taxes by £12,570 × 20% / 12 = £210/month.

For a higher-rate earner mistakenly on BR at a second job: under-taxes — they should pay 40% but BR only charges 20%. The 20% shortfall becomes a self-assessment bill at year-end.

Worked comparison — £35,000 salary, first month of a new job

Code	Tax this month	vs correct 1257L
1257L cumulative	£374	baseline
1257L M1	£374 if month 1 is the only pay month; higher later	higher if starting mid-year
0T	£583	+£209/month over-tax
BR	£583	+£209/month over-tax

Compounded over 3-4 months of emergency coding: £600-£800 over-paid.

How to fix it — the 5-step path

1. Give your employer your P45

If you left your previous job recently, locate the P45 and hand parts 2 + 3 to your new employer. Most employers can process it same-day; HMRC updates the code within 1-2 pay periods.

2. If no P45, complete the Starter Checklist

Your employer provides the form (or links to gov.uk’s version). Three statements to choose:

• Statement A: this is your first job since 6 April and you have no other income → get 1257L
• Statement B: this is currently your only job → get 1257L W1/M1 temporarily
• Statement C: you have another job / pension → get BR

Most new hires should tick A or B. Ticking C when you shouldn’t triggers unnecessary BR.

3. Log into your Personal Tax Account

Go to gov.uk/personal-tax-account. The “Check your Income Tax” section shows:

• The current code HMRC has on file for each of your employers
• Their breakdown of your estimated annual income
• Any adjustments (benefits, prior-year tax, company car)

If the code is wrong, use the “Update your details” link or call HMRC.

4. Call HMRC if the code doesn’t update

HMRC Income Tax helpline: 0300 200 3300. Have your National Insurance number and your employer’s PAYE reference (on your payslip) ready. They can push an updated code to your employer within the same pay period in many cases.

5. Wait for the automatic reconciliation

Once HMRC issues a cumulative 1257L to your employer, the very next pay period recalculates your year-to-date tax position and refunds any overpayment through that payslip. You don’t need to file self-assessment for an emergency-tax refund; PAYE handles it natively.

If the emergency coding persists past the end of the tax year (6 April next year), HMRC issues a P800 calculation around June/July showing the overpayment and prompting a refund via bank transfer or your current year’s tax code.

When to claim a manual refund

Rarely needed. PAYE almost always catches up. But manual claims via gov.uk/claim-tax-refund apply if:

• You left the UK mid-year (complete form P85)
• You stopped working permanently mid-year (form P50)
• It’s been more than 6 weeks since you became entitled to a refund and the code still hasn’t updated

Prevention for next time

1. Always get your P45 from each employer when you leave — it’s legally required for them to issue it.
2. Complete the Starter Checklist immediately at a new job, even if you know the P45 is coming. Statement A or B will prevent 0T / BR defaults.
3. Check your Personal Tax Account in the first week of any new job. If the code looks wrong, fix it while the overpayment is small.
4. Watch for the M1, W1 or X suffix on payslips. That’s the emergency marker. Once it clears (code becomes plain 1257L), the cumulative calculation runs.

Related

• Tax code explainer — hub for every letter and what it means
• Emergency code detail — in-depth for W1/M1/X suffixes
• 0T code detail — in-depth for the “no PA” temp code
• PAYE explained — how the system handles cumulative vs non-cumulative coding
• Salary calculator — model what your take-home should be so you spot when it’s wrong