What is an emergency tax code and why am I on it?

An emergency tax code is a temporary code assigned by HMRC when they do not have enough information about your income history or past employments. This frequently occurs when you start a new job without a P45, start your first job, or return to work after being self-employed. It ensures tax is deducted until your correct code is calculated.

What are the main emergency tax code reasons for new employees?

The most common reasons include: starting a new job without giving your employer a P45 form from your previous job; starting a second job while keeping your first job (which uses your Personal Allowance); starting work part-way through the tax year; or if HMRC has not yet processed your new starter checklist.

How much tax do I pay on a br tax code flat rate?

On a BR (Basic Rate) tax code, you pay a flat 20% tax on all of your earnings from the very first pound. No tax-free Personal Allowance (£12,570) is applied to this source of income. It is commonly applied to second jobs or pensions where your first job is already using your standard allowance.

How can I submit an emergency tax refund claim to HMRC?

In most cases, you do not need to make a formal claim. Once your employer submits your new starter checklist or HMRC calculates your correct code, they will send an electronic coding notice (P6) to your employer. Your employer's payroll will then automatically adjust your tax and issue a refund on your next payday. If the tax year has ended, you can claim a refund online through your HMRC Personal Tax Account.

What is the difference between cumulative and non-cumulative tax codes?

A cumulative tax code calculates your tax based on your total earnings and allowances from the start of the tax year to the current pay date. A non-cumulative tax code (marked as W1, M1, or X) looks at the current pay period in isolation, ignoring any past pay or tax paid. This means any overpaid tax will not be refunded automatically through payroll until the code is changed to a cumulative one.

What does tax code 1257L W1 or 1257L M1 mean?

These are emergency codes. The digits 1257 mean you are entitled to the standard personal allowance of £12,570. However, the W1 (Week 1) or M1 (Month 1) suffixes indicate that the allowance is applied non-cumulatively. You receive exactly 1/52nd (weekly) or 1/12th (monthly) of your allowance in each pay packet, with no rollover of unused allowance from previous periods.

How long does it take for HMRC to change my emergency tax code?

It typically takes HMRC 2 to 4 weeks to update your tax code once your employer submits your new starter checklist or P45. Once HMRC updates your code, they will notify your employer automatically. You can check your tax code status online in real-time through the HMRC app.

What should I do if my emergency tax code is not corrected after two months?

If your code is not corrected after two payroll runs, you should check that your employer has submitted your new starter details. If they have, you should log into your HMRC Personal Tax Account online or call HMRC directly to explain your situation and request a tax code review.

Emergency Tax Calculator UK: Check Code & Refund (2026/27)

Emergency Tax Code Refund & Overpayment Calculator

✓ 2026/27 Tax Year Verified

Calculate your emergency tax deductions under non-cumulative codes (1257L W1/M1/X, 0T, BR, D0), estimate your overpaid tax refund from HMRC, and discover how to correct your tax code immediately.

Popular Annual Salaries:

Tax & Employment Details

Gross Pay / Salary

Salary Input Frequency

Emergency Tax Code on Payslip Look next to your tax code on your payslip for 'W1', 'M1', or 'X'.

Number of Pay Periods on Emergency Tax

months

How many paychecks have been taxed under this emergency code.

HMRC Starter Checklist Simulator:

Statement B: Only job now, but had another job since 6 April (Gives 1257L M1/W1) Statement A: First job since 6 April, no other income/benefits (Gives 1257L Cumulative) Statement C: Have another job or receive a pension (Gives BR or 0T)

Total Earnings Before This Job (Current Tax Year)

If you had a gap in work or were unemployed, enter £0 to see your full unused allowance refund.

Estimated Overpaid Tax Refund Owed

£1,121

Refundable to you automatically or via HMRC claim

Emergency Tax Paid (Elapsed)

£1,750

over 3 months

Correct Cumulative Tax Due

£629

statutory tax liability

Take-Home Pay Comparison (Per Paycheck)

Emergency Net Take-Home (Current) £2,204.00

Correct Standard Net Take-Home £2,578.00

Monthly Shortfall / Cash Drag -£374.00 /mo

Total Refund Lump Sum Due £1,121.00

🛡️

Verified for Accuracy (2026/27 Tax Year)

Fact-checked and audited by David Vance, CTA FCA, Chartered Tax Advisor & Accountant. Verified against official HMRC rules.

How We Calculated This

Identify the Specific Emergency Tax Code: Look for indicator codes on your payslip. The most common uk emergency tax codes 2026 are 1257L W1, 1257L M1, or 1257L X. Other flat-rate emergency codes include BR (Basic Rate), D0 (Higher Rate), or OT (no allowance and taxed at standard bands).
Apply Non-Cumulative Calculations: Standard tax codes allocate 1/12th of your Personal Allowance each month and compile your year-to-date earnings cumulatively. In contrast, emergency codes ending in W1 or M1 are non-cumulative. They ignore all past earnings and taxes paid in the tax year, applying exactly 1/12th of your £12,570 Personal Allowance (£1,047.50) to your earnings for that month in isolation.
Apply Flat-Rate Tax Deductions: For BR or D0 codes, treat your personal allowance as zero. On a br tax code flat rate, deduct a flat 20% from the first pound of your gross earnings. On a D0 code, deduct a flat 40% from the first pound. On an OT code, calculate progressive tax bands starting from £0 with no personal allowance protection.
Calculate Excess Tax Paid: Compare the tax deducted under the emergency code against what you would have paid under a standard cumulative tax code. The difference represents the overpaid tax that is eligible for a refund.
Determine the Emergency Tax Code Reasons: Understand why you were placed on the code. Common emergency tax code reasons include starting a new job without a P45 form, starting your first job, having multiple concurrent jobs where your Personal Allowance was not allocated correctly, or returning to employment after a period of self-employment.
Initiate the Emergency Tax Refund Claim: Once your details are updated, your employer\'s payroll will automatically recalculate your cumulative tax on your next payday and issue a refund directly through your paycheck. If the tax year has ended, you must make an emergency tax refund claim online via your HMRC Personal Tax Account or wait for HMRC to issue a P800 tax calculation notice.

Real-World Examples

Detailed Math for £3,000.00 Monthly Earnings on Tax Code BR (Second Job)

This scenario details the exact step-by-step mathematical calculations for an employee earning £3,000.00 gross per month whose employer applies the flat-rate BR code, comparing it to standard coding.

Step 1: Gross Monthly Salary = £3,000.00
Step 2: Apply BR Code Rules (No Personal Allowance, flat 20% rate):
        Taxable Income = £3,000.00
        Monthly Income Tax deducted = £3,000.00 * 0.20 = £600.00
Step 3: Compare with Standard Code (1257L Cumulative, 1/12th of PA applied):
        Monthly Personal Allowance = £12,570.00 / 12 = £1,047.50
        Taxable Income = £3,000.00 - £1,047.50 = £1,952.50
        Correct Monthly Tax = £1,952.50 * 0.20 = £390.50
Step 4: Calculate Overpaid Tax:
        Monthly Overpayment = £600.00 - £390.50 = £209.50
        (If on this code for 4 months, you will overpay a total of £838.00 in tax.)

Detailed Math for £2,000.00 Earnings in Month 2 on Code 1257L M1 (Non-Cumulative)

This scenario details how a Month 1 emergency code affects tax deductions for fluctuating incomes. In Month 1, the employee earned £1,000, and in Month 2, they earn £2,000.

Step 1: Month 2 Gross Salary = £2,000.00
Step 2: Apply 1257L M1 Rules (1/12th of Personal Allowance applied in isolation):
        Personal Allowance for Month 2 = £12,570.00 / 12 = £1,047.50
        Taxable Income in Month 2 = £2,000.00 - £1,047.50 = £952.50
        Month 2 Income Tax deducted = £952.50 * 0.20 = £190.50
Step 3: Compare with standard cumulative calculation (where Month 1 and Month 2 are combined):
        Total YTD Earnings = £1,000 (Month 1) + £2,000 (Month 2) = £3,000.00
        Total YTD Allowance = £1,047.50 * 2 = £2,095.00
        Total Taxable YTD = £3,000.00 - £2,095.00 = £905.00
        Total Correct YTD Tax = £905.00 * 0.20 = £181.00
        (Under standard cumulative payroll, you would pay a total of £181.00 tax by Month 2. Under the emergency code, you pay £190.50 in Month 2 alone, causing an overpayment.)

Related Calculators

Frequently Asked Questions

What is emergency tax and why am I paying it?

Emergency tax is a temporary tax code applied when HMRC does not have your correct tax details. This commonly occurs when you start a new job without a P45 form or are returning to work after a gap.

How do I claim back overpaid emergency tax?

Once your employer receives your correct tax code from HMRC (or through a Starter Checklist), your payroll software will automatically adjust your next payslip and refund any overpaid tax in that month. You do not usually need to contact HMRC directly.

Emergency Tax Code Calculator & HMRC Refund Estimator (2026/27)