Tax code 1150L M1 is an emergency tax code from the 2017/18 UK tax year. The 1150 reflected the personal allowance of £11,500 that applied then, and the M1 told your employer to work out your tax month by month rather than across the whole year. If you’re looking at an old payslip or P60, that’s what it meant at the time. If your current payslip still shows 1150L M1, the code is wrong: the standard code has been 1257L since the personal allowance rose to £12,570 in April 2021, and you should contact HMRC to get it fixed.
What the 1150 Number Represented
The numbers in any UK tax code tell your employer how much you can earn tax-free in the year. Multiply by ten and add the last digit back to get the allowance in pounds. So 1150 stood for £11,500, which was the standard personal allowance for the 2017/18 tax year. The L confirmed you were entitled to that standard allowance with no special adjustments — the most common suffix on UK payslips.1GOV.UK. Tax Codes: What Your Tax Code Means
The personal allowance has since risen to £12,570, and Parliament has frozen it at that level through at least April 2028.2GOV.UK. Income Tax: Maintaining the Personal Allowance and the Basic Rate Limit The standard code today is 1257L. HMRC instructs employers to automatically update L codes when the personal allowance changes, so the right figure normally carries into each new tax year without you needing to do anything.3HM Revenue & Customs. PAYE Manual – PAYE11075 – Coding: Codes: Suffix Codes: The Suffix If yours didn’t, that’s a red flag worth chasing.
What the M1 Suffix Means
M1 stands for “Month 1” and puts you on a non-cumulative basis.4GOV.UK. Tax Codes: Emergency Tax Codes Each payslip is treated as if it were the first month of the tax year. Your employer ignores what you earned and paid in tax during earlier months and works out the deduction based only on what you’re paid this period.5HM Revenue & Customs. PAYE Manual – PAYE11090 – Coding: Codes: Ways an Employer Can Operate a Code
Under a normal cumulative code, payroll tracks your running totals across the year. If you earned nothing for the first three months and then started work in month four, a cumulative code would credit those unused months of personal allowance to you, often producing a lower tax bill or a refund in that payslip. The M1 basis blocks that. You get exactly one-twelfth of your annual allowance each month, regardless of what happened before.
M1 comes in three variants depending on how often you’re paid:4GOV.UK. Tax Codes: Emergency Tax Codes
- W1 for weekly-paid employees
- M1 for monthly-paid employees
- X where pay dates vary
Some payslips show “NONCUM” instead. The effect is the same.
Why M1 Can Hurt in Bonus Months
Because M1 treats each month in isolation, a bonus or a big overtime month can be taxed harder than under a cumulative code. Payroll treats that inflated pay as though you earn the same amount every month of the year.4GOV.UK. Tax Codes: Emergency Tax Codes A single payment that pushes your monthly figure above £4,189 (one-twelfth of the higher-rate threshold) gets 40% applied to the excess for that month, even if your actual annual salary sits comfortably in the basic-rate band. A cumulative code would spread the allowance across all months and usually keep you out of higher-rate territory. Any overtaxed amount gets corrected once HMRC moves you onto a proper cumulative code or at year-end reconciliation.
Why You Ended Up on an Emergency Code
HMRC uses emergency codes when it doesn’t have enough information to tax you accurately.4GOV.UK. Tax Codes: Emergency Tax Codes The usual trigger is starting a new job without giving your P45 to your new employer. The P45 carries pay and tax details from your previous role, and without it, payroll has no way to continue where your old employer left off.
Other situations that produce an emergency code:
- Returning to work after a long career break
- Starting your first job
- Taking on a second job alongside your main one
- Moving from self-employment into PAYE
The emergency code stops big underpayments building up while HMRC catches up on your details. It’s not a penalty. It slightly overtaxes you in the short term to prevent a large bill later.
If you can’t provide a P45, your new employer should give you a Starter Checklist to complete.6GOV.UK. Starter Checklist if Youre Starting a New Job It collects your National Insurance number, start date, whether you’ve had another job or received certain benefits since the previous 6 April, and student loan details. Completing it doesn’t always avoid an emergency code, but it gives payroll enough to assign a more accurate one from day one. Skipping fields is one of the most common reasons people spend months on the wrong code.
How to Get the Code Corrected
The fastest way is the “Check your Income Tax” service on GOV.UK.7GOV.UK. Tax Codes: How to Update Your Tax Code Sign in with your Government Gateway or GOV.UK One Login account, review your employment details, income estimate, and any company benefits, and update anything that’s wrong or missing. If you can’t use the online service, HMRC’s Income Tax helpline can do it over the phone.8GOV.UK. Check Your Income Tax for the Current Year
Once HMRC has the right information, it issues a coding notice (sometimes called a P6) to your employer with instructions to switch you to a cumulative code.9GOV.UK. Understanding Your Employees Tax Codes: Changes During the Tax Year Your employer then recalculates your tax for the year so far. Any overpayment from the emergency period comes back through your next payslip. The sooner you make the call, the sooner the money lands.
Getting Back the Tax You Overpaid
If the code gets corrected while the tax year is still running, payroll refunds the overpaid tax automatically when they move you onto the cumulative basis. You’ll usually see it as a larger-than-usual net pay in the pay period after the new code takes effect.
If the tax year ends first, HMRC’s automated reconciliation picks it up. After 5 April, HMRC compares the pay and tax your employer reported against what you should have owed. Where you overpaid, they send a P800 tax calculation letter. These go out between June and the following March.10GOV.UK. Tax Overpayments and Underpayments The P800 sets out what you’re owed and how to claim it: online for a direct bank transfer, or by waiting for a cheque. A P800 isn’t a penalty and doesn’t mean you did anything wrong. It’s the system reconciling the mismatch the emergency code created.