The BR W1M1 tax code means your employer is taking 20 percent income tax from every pound of your pay, with no tax-free Personal Allowance applied, and working that tax out on each pay period on its own instead of across the whole tax year. For most people it’s a temporary emergency code, and it usually results in overpaying tax. Once HMRC has the right information about your job, the code gets replaced and any overpayment can be refunded.
What the Code Actually Does to Your Pay
“BR” stands for Basic Rate. Your employer deducts 20 percent income tax on everything you earn from that job, with no tax-free amount taken off first.1GOV.UK. Understanding Your Employees Tax Codes Under a standard code like 1257L, the first £12,570 of annual income is sheltered by the Personal Allowance.2House of Commons Library. Direct Taxes: Rates and Allowances BR removes that shelter entirely. Every pound gets taxed at 20p.
The W1 or M1 that follows tells payroll to treat each pay period as if it were the first of the tax year. W1 applies if you’re paid weekly, M1 if you’re paid monthly.3GOV.UK. Tax Codes: Emergency Tax Codes Under a normal cumulative code, payroll adds up your earnings and tax paid since 6 April and adjusts each payslip so the running total stays right. With W1 or M1, the software can’t look back, so mistakes don’t self-correct during the year.4GOV.UK. Understanding Your Employees Tax Codes – Section: If Your Employees Tax Code Has W1 or M1 at the End
The logic HMRC applies is this: your Personal Allowance is presumably being used against another job or a pension already, so taxing this income flat at 20 percent should give the right answer. If that assumption is wrong, you overpay until the code is fixed.
Why You Ended Up on It
The BR W1M1 code almost always traces back to missing or ambiguous information about your employment.
You Started a Job Without Handing Over a P45
When you leave a job, your former employer gives you a P45 showing pay and tax so far this year. Passing it to a new employer lets payroll pick up where the last one left off. Without it, HMRC may put you on an emergency code until things are sorted.3GOV.UK. Tax Codes: Emergency Tax Codes
You Ticked Statement C on the Starter Checklist
Without a P45, your employer asks you to complete a starter checklist with three statements. Statement C is the one that triggers a BR code, and you should only select it if you have another job or receive a state, workplace, or private pension.5GOV.UK. Starter Checklist Statement A gives you the full Personal Allowance, and Statement B applies it on a non-cumulative basis. Ticking C by mistake when this is actually your only job is one of the most common reasons people find themselves overtaxed.
You Genuinely Have a Second Income
If you have two jobs, or a pension alongside employment, HMRC assigns your Personal Allowance to your main income and taxes the rest at the basic rate. In that case BR is correct, and the W1/M1 suffix stays on until HMRC confirms the arrangement.1GOV.UK. Understanding Your Employees Tax Codes
What It Costs You Each Month
Someone earning £2,500 a month loses £500 to income tax under BR W1M1. On a standard 1257L code, the tax on the same pay would be around £247, because the first £1,047.50 each month is covered by the Personal Allowance. That’s roughly £253 a month extra coming out of your pay until the code changes.
The code only affects income tax. National Insurance and student loan repayments carry on as normal, and pension contributions come off under your usual scheme rules.
When 20 Percent Isn’t Enough
There’s a wrinkle for higher earners. BR taxes everything at 20 percent, but the higher rate of 40 percent applies to income above £50,270, and the additional rate of 45 percent kicks in above £125,140.2House of Commons Library. Direct Taxes: Rates and Allowances If your combined income from all sources sits in the higher band, BR on a second job actually undertaxes you, and HMRC will catch up later with a bill. If you know your total income exceeds £50,270, contact HMRC so the second source can be moved to a D0 code, which deducts at 40 percent.
How to Get the Code Changed
There are three practical routes, and the online one is fastest.
Through Your Personal Tax Account
Sign in to the “Check your Income Tax” service on GOV.UK or use the HMRC app. You can see the code applied by each employer, update employment details, and flag anything that looks wrong.6GOV.UK. Check Your Income Tax for the Current Year You’ll need your National Insurance number and Government Gateway login.
By Giving Your Employer a P45
If you have a P45 you haven’t yet passed on, give it to payroll. It carries your previous pay, tax deducted, and leaving code, which is often enough to trigger the right code straight away.3GOV.UK. Tax Codes: Emergency Tax Codes
By Phone
If online isn’t an option, call the HMRC Income Tax helpline on 0300 200 3300, Monday to Friday, 8am to 6pm. Have your National Insurance number, employer name, and PAYE reference ready.
Whichever route you use, HMRC updates the code and notifies you and your employer within 15 working days.7GOV.UK. Tax Codes: If You Think Your Tax Code Is Wrong Your next payslip after your employer receives the new code should show the corrected deductions.
Getting Overpaid Tax Back
If BR W1M1 ran for several pay periods before being corrected, you’ve probably overpaid. How the refund reaches you depends on when the fix happens.
If the Code Is Corrected During the Tax Year
When your code is switched to a cumulative one before 5 April, payroll recalculates your tax from the start of the tax year, subtracts what you’ve already paid, and returns any overpayment through your next payslip. It shows up as a larger pay packet, and you don’t need to claim separately.
If the Tax Year Has Already Ended
After the tax year closes, HMRC reviews PAYE records and sends a P800 calculation if your tax doesn’t reconcile. Since May 2024 most refunds are no longer sent out automatically. You need to claim, either online, through the HMRC app, or by phone.8GOV.UK. If Your Tax Calculation Letter (P800) Says You Are Due a Refund
Claim online and the money usually arrives within five working days. Ask for a cheque and it takes up to six weeks.8GOV.UK. If Your Tax Calculation Letter (P800) Says You Are Due a Refund You have four years from the end of the tax year to claim, so a refund for 2025–26 must be claimed by 5 April 2030.
Scottish and Welsh Equivalents
If your main home is in Scotland your tax code starts with “S,” and the equivalent code is SBR. The Scottish basic rate is also 20 percent, though Scotland has a starter rate at 19 percent and an intermediate rate at 21 percent that don’t exist elsewhere in the UK.9mygov.scot. Tax Codes In Wales the code starts with “C,” making the equivalent CBR.1GOV.UK. Understanding Your Employees Tax Codes SBR W1M1 or CBR W1M1 work the same way as BR W1M1, just with the relevant regional bands.