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

“Why has my first pay packet taken so much tax?” is one of the most common questions new employees ask. The usual cause is the starting tax code a new employer has to use before HM Revenue and Customs (HMRC) has your full details. It is temporary, and overpaid tax normally comes back through payroll once the right code arrives.

What “emergency tax” actually means

On gov.uk, an emergency tax code is one that ends in W1 (weekly pay), M1 (monthly pay) or X (pay dates vary), or shows as “NONCUM” on a payslip (gov.uk). Tax is then worked out on that week’s or month’s pay alone, as if you were paid that amount all year, instead of on your total pay so far in the tax year.

People also use “emergency tax” for two other starting codes:

1. 0T: no Personal Allowance, but the normal 20% / 40% / 45% bands still apply.
2. BR: every pound taxed at the basic rate (20%), no Personal Allowance. This is the normal code for a second job.

All of these can take more tax than the settled code (usually 1257L) in the short term.

Why a new employer uses one

The Starter Checklist decides the first code

If you do not hand in Parts 2 and 3 of a P45 from your previous job, your new employer asks you to choose a statement on the Starter Checklist. The statement you choose, or a refusal to choose, sets the code the employer starts with (PAYE61030):

Statement	What it says (in short)	Starting code
A	First job since 6 April; no taxable Jobseeker’s Allowance, Employment and Support Allowance, taxable Incapacity Benefit, or state or occupational pension	Emergency code (1257L) on a cumulative basis
B	Now your only job, but since 6 April you have had another job or those benefits; no state or occupational pension	Emergency code on a Week 1 / Month 1 basis (1257L W1 / M1)
C	You have another job or a state or occupational pension	BR
None	No statement signed	0T on a Week 1 / Month 1 basis

So Statement A gives you your full Personal Allowance from the start; Statement B gives it non-cumulatively, because an earlier job this year may already have used some of it; Statement C puts the job on BR, because your allowance is expected to be used elsewhere. Choose the statement that is true.

HMRC has not yet matched your details

When you are first paid, your new employer tells HMRC you have started. HMRC usually updates your code once it has details from your new and previous employers, and sends it to you and the employer. This can take up to 35 days from when you start (gov.uk).

You start getting company benefits or the State Pension

gov.uk notes you might be put on an emergency code when you start getting company benefits or the State Pension, and stay on it until the end of the tax year, moving to a normal code in the new year.

How much extra tax are you paying?

The figures below are approximate, use rest-of-UK 2026/27 rates and ignore National Insurance. Payroll uses HMRC’s PAYE tables, which can differ from these by a few pence.

1257L W1 / M1 / X (non-cumulative, full allowance)

Each pay period gets roughly 1/52 of the Personal Allowance a week (about £242) or 1/12 a month (about £1,048), in isolation. Suppose your first monthly pay is £3,000 and it arrives in month 7 of the tax year, with no other pay earlier in the year. A cumulative code would give you 7/12 of the £12,570 allowance (about £7,333) against that pay, so no tax. Month 1 gives only one month’s share: tax on £3,000 − £1,048 at 20% = about £391.

0T (no allowance)

On a £35,000 salary paid monthly (about £2,917 a month), all of which falls within the basic-rate band:

• 0T: £2,917 × 20% = about £583
• 1257L: (£2,917 − £1,048) × 20% = about £374
• Extra tax: about £210 a month

BR (basic rate on everything)

For someone whose only job is wrongly on BR, the loss of the allowance costs about the same: roughly £210 a month at this salary.

For a higher-rate earner on BR at a second job (correctly, because the allowance is used at the main job), BR can under-tax: income in the higher-rate band at the second job should pay 40% but BR deducts only 20%. HMRC collects the shortfall later, usually through a P800 or a change to your tax code.

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

Code	Tax this month (approx.)	vs settled 1257L
1257L cumulative	£374	baseline
1257L M1	£374 every month	same in month 1; if you start mid-year with no earlier pay, a cumulative code would take less
0T M1	£583	+£210
BR	£583	+£210

On 0T or BR at this salary, two months before the code is corrected means about £419 overpaid, three months about £629. It comes back once the new code is used (see step 5).

How to fix it: the 5-step path

1. Give your employer your P45

When you leave a job your employer should give you a P45; the PAYE Regulations require the employer to complete it when your employment ends (reg.36). Give Parts 2 and 3 to your new employer and keep Part 1A (gov.uk). If your old employer has not given you one, ask for it.

2. If you have no P45, complete the Starter Checklist accurately

Your employer gives you the Starter Checklist. Pick the statement that matches your situation (table above). Leaving it blank puts you on 0T Week 1 / Month 1; ticking C when it does not apply puts you on BR.

3. Check your Personal Tax Account

Your Personal Tax Account shows the tax code HMRC holds for each employer and the income it has used to set it. If the code is still wrong more than 35 days after you started, gov.uk says to update your tax code details.

4. Contact HMRC if it is still wrong

The Income Tax helpline is 0300 200 3300, Monday to Friday 8am to 6pm (gov.uk). Have your National Insurance number and your employer’s PAYE reference (on your payslip) ready.

5. Let payroll refund the overpayment

When HMRC updates your code and has all your income details for the year, it works out what you overpaid and asks your employer to refund the difference in your pay, usually when the new code is used. If you are paid monthly the employer should use the new code on your next or the following pay; weekly, on your third pay (gov.uk). You do not need to file a Self Assessment return for this.

If the tax year ends before it is put right, HMRC sends a tax calculation letter (P800) or a Simple Assessment letter. These are sent between June and March of the following tax year (gov.uk). If the P800 says you can claim online, the money arrives within 5 working days of an online claim.

When to claim a refund yourself

Usually you do not need to. But use gov.uk’s refund checker if, for example:

• you have stopped working, are not claiming taxable benefits or getting a pension, and have not started a new job (form P50)
• you left the UK part-way through the tax year
• you think you overpaid and HMRC has not sent you a P800

Prevention for next time

1. Get your P45 from each employer when you leave, and give it to the next one.
2. Complete the Starter Checklist at a new job if you have no P45. The right statement avoids an unnecessary 0T or BR start.
3. Check your Personal Tax Account in the first weeks of a new job.
4. Watch for W1, M1, X or NONCUM on your payslip. Once the code has none of these, tax is worked out cumulatively again.

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