Getting a different tax code on your payslip can be confusing — and worrying if it means more tax is taken. This guide explains why tax codes change, what the letters and numbers mean, and how to check if HMRC got it right.
What Is a Tax Code?
Your tax code tells your employer or pension provider how much tax-free income you’re entitled to before they start deducting tax.
Standard tax code 2026/27: 1257L
This means:
- 1257 = £12,570 tax-free allowance (multiply by 10)
- L = You’re entitled to the standard Personal Allowance
Your employer uses this code to calculate tax on each pay period.
Common Reasons Your Tax Code Changed
1. New Tax Year Adjustments
At the start of each tax year (6 April), HMRC updates codes to reflect:
- New Personal Allowance thresholds
- Continued collection of underpaid tax from previous years
- Updated benefit in kind values
Example: Moving from 1257L to 1257L is normal — no change. But 1150L suggests HMRC is collecting something.
2. You Started a New Job
When you start a new job without a P45 from your previous employer, your new employer may:
- Use emergency tax code (often 1257L M1 or W1)
- Use BR (basic rate on everything)
- Wait for HMRC to issue a correct code
Once HMRC receives information from both employers, your code updates.
3. You Have Multiple Jobs
If you have two jobs, only one gets your full Personal Allowance:
- Main job: 1257L (full allowance)
- Second job: BR (20% on all earnings) or D0 (40% on all)
HMRC may split your allowance between jobs — e.g., first job gets 600L, second gets 657L.
4. Company Benefits (Benefit in Kind)
If you receive taxable benefits from your employer, the value is deducted from your allowance:
| Benefit | Typical Tax Code Impact |
|---|---|
| Company car | -£2,000 to -£10,000+ |
| Private medical insurance | -£500 to -£2,000 |
| Fuel card (private use) | -£3,000 to -£7,000 |
| Gym membership | -£300 to -£1,000 |
Example: If you have a £3,000 car benefit, your code might change from 1257L to 957L.
5. State Pension / Private Pension
When you start receiving a pension alongside employment income:
- HMRC reduces your employment tax code to collect tax on the pension
- Your code might drop significantly (e.g., 1257L → 657L)
This ensures you pay the right tax across all income sources.
6. Underpaid Tax From Previous Year
If HMRC calculates you underpaid tax last year, they recover it by:
- Reducing your tax code for the current year
- Recovering the debt gradually through PAYE
Example: £1,200 underpaid tax → code reduced by 120 (to collect over the year)
7. Marriage Allowance
If you transfer Marriage Allowance to/from your spouse:
- Receiving spouse: Code increases (e.g., 1257L → 1382L)
- Giving spouse: Code decreases (e.g., 1257L → 1132L)
8. Estimated Self-Employment Income
If HMRC knows you have self-employment income, they may reduce your employment tax code to collect tax throughout the year instead of via Self Assessment.
Tax Code Letters Explained
| Letter | Meaning |
|---|---|
| L | Standard Personal Allowance |
| M | You’ve received Marriage Allowance from spouse |
| N | You’ve transferred Marriage Allowance to spouse |
| T | Your allowance needs review (complex calculation) |
| 0T | No Personal Allowance (often means earning over £125,140) |
| BR | All income taxed at Basic Rate (20%) |
| D0 | All income taxed at Higher Rate (40%) |
| D1 | All income taxed at Additional Rate (45%) |
| NT | No Tax — special circumstances |
| S | Scottish income tax rates apply |
| C | Welsh income tax rates apply |
| K | Your deductions exceed your allowance (tax code adds to income) |
What Does K Code Mean?
A K code means your benefits in kind and other deductions exceed your Personal Allowance. Instead of reducing your allowance, HMRC adds the excess to your taxable income.
Example: K475 means HMRC adds £4,750 to your taxable income, then calculates tax on the total.
What Do W1 and M1 Mean?
| Suffix | Meaning |
|---|---|
| W1 (Week 1) | Emergency tax — each week treated separately, ignoring previous weeks |
| M1 (Month 1) | Emergency tax — each month treated separately |
These are temporary codes used when HMRC doesn’t have full information. Once sorted, you should receive a cumulative code and potential refund.
How to Check Your Tax Code
1. Personal Tax Account (Best Method)
- Go to gov.uk/personal-tax-account
- Sign in with Government Gateway
- Select “Check your Income Tax”
- View your tax code and how it’s calculated
You’ll see:
- Current tax code
- Estimated income from each source
- Benefits in kind
- Any tax owed/collected
2. Check Your Payslip
Your tax code appears on every payslip. Compare month-to-month to spot changes.
3. P2 Coding Notice
HMRC sends a P2 notice when they change your code. It explains:
- Your new tax code
- How they calculated it
- What to do if you disagree
These sometimes arrive after the change takes effect.
4. HMRC App
Download the HMRC app to check your tax code, estimated tax, and update your details on the go.
What If My Tax Code Is Wrong?
Signs Your Code May Be Wrong
- You’re on BR but only have one job
- Your code includes benefits you no longer receive (old company car)
- You’re on emergency tax weeks after starting a job
- Your estimated income looks wrong
- You stopped receiving state pension but it’s still deducted
How to Fix It
- Log into Personal Tax Account
- Update your employment details
- Tell HMRC about changes — removed benefits, stopped second job, etc.
- Call HMRC on 0300 200 3300 if you can’t fix it online
HMRC will issue a new code to your employer.
Getting a Refund
If you overpaid tax due to a wrong code:
- HMRC may refund via PAYE (reduced deductions going forward)
- You might receive a cheque or bank transfer
- P800 tax calculation sent after year end shows if you’re owed money
Common Tax Code Scenarios
Scenario 1: New Job, No P45
Situation: Started new job without giving employer your P45.
What happens: Employer uses emergency tax code (1257L W1/M1 or BR).
Solution: Give employer your P45, or let them know this is your only job. HMRC will update your code within weeks.
Scenario 2: Second Job Started
Situation: You start a second job.
What happens: Second employer might use BR (20% on all), or HMRC splits your allowance.
Check: Log into Personal Tax Account — ensure your allowance isn’t being used twice (this would mean underpaid tax later).
Scenario 3: Company Car Changed
Situation: You returned your company car but code still includes it.
Solution: Tell HMRC via your Personal Tax Account — update benefits section. Your code should increase.
Scenario 4: Pension Started
Situation: You started receiving private/state pension alongside work.
What happens: HMRC reduces your employment tax code to collect tax on pension income.
This is correct — but check the pension income figure matches reality.
Scottish and Welsh Tax Codes
Scottish Tax Codes (S Prefix)
If you live in Scotland, your code starts with S:
- S1257L = Scottish taxpayer with standard allowance
Scotland has different income tax bands:
| Band | Rate |
|---|---|
| Starter | 19% |
| Basic | 20% |
| Intermediate | 21% |
| Higher | 42% |
| Top | 47% |
Welsh Tax Codes (C Prefix)
If you live in Wales, your code starts with C:
- C1257L = Welsh taxpayer with standard allowance
Currently, Welsh rates match England, but the code identifies you as a Welsh taxpayer.
Tax Code Quick Reference
| If Your Code Is… | It Means… |
|---|---|
| 1257L | Standard — £12,570 tax-free |
| Higher than 1257L | You have extra allowances (Marriage Allowance received, Blind Person’s Allowance) |
| Lower than 1257L | Something reduces your allowance (benefits in kind, underpaid tax, pension income) |
| BR | 20% tax on all earnings, no allowance |
| 0T | No Personal Allowance (high earner or missing information) |
| K code | Deductions exceed allowance — amount added to income |
| W1/M1 | Emergency — temporary, non-cumulative |
| NT | No tax deducted |
Related Guides
- UK Income Tax Guide 2026/27 — Tax bands explained
- Emergency Tax Explained — How to fix it
- Marriage Allowance Guide — Transfer allowance to spouse
- Personal Allowance Explained — £12,570 tax-free
- How to Check Your Tax Code — Step by step
Tax codes can be confusing — but they’re usually right. If yours looks wrong, check your Personal Tax Account or call HMRC on 0300 200 3300. Getting it fixed ensures you don’t overpay (or underpay) tax.