UK Tax Codes Explained 2026/27 — What Your Code Means and How to Fix ItTax Code Checker Guide UK 2026 — Common Mistakes & How to Fix Them
Understand your tax code, check it's correct, and fix errors that cost you money. Millions of Britons are on the wrong tax code.
For a comprehensive overview of income tax, see our Income Tax guide.
Your tax code determines how much tax you pay. Get it wrong and you could be overpaying — or face an unexpected bill. Here’s how to check yours.
Understanding Tax Codes
Common Tax Codes Explained
| Code | Meaning | Who Has It |
|---|
| 1257L | Standard code — £12,570 allowance | Most employees |
| BR | Basic Rate — all income taxed at 20% | Second job (usually) |
| D0 | Higher Rate — all taxed at 40% | Second job (high earner) |
| D1 | Additional Rate — all taxed at 45% | Very high earners |
| NT | No Tax | Certain circumstances |
| 0T | No allowances | Allowances used elsewhere |
| K | You owe extra | Benefits, reduced allowances |
| S | Scottish taxpayer | Lives in Scotland |
| C | Welsh taxpayer | Lives in Wales |
Breaking Down the Code
1257L Explained:
| Part | Meaning |
|---|
| 1257 | £12,570 allowance (multiply by 10) |
| L | Standard Personal Allowance applies |
Other Letters:
| Letter | Meaning |
|---|
| L | Standard Personal Allowance |
| M | Marriage Allowance received |
| N | Marriage Allowance transferred |
| T | HMRC reviewing your code |
| W1/M1 | Emergency — non-cumulative |
| X | Special circumstances |
Is Your Code Correct?
Quick Check
| Your Situation | Expected Code |
|---|
| Single job, standard circumstances | 1257L |
| Receiving Marriage Allowance | 1383L or similar |
| Transferring Marriage Allowance | 1194N |
| Two jobs | 1257L (main) + BR (second) |
| Company benefits (car, health) | Lower number (e.g., 1100L) |
| State Pension + job | Reduced number |
| Student loan | No effect on code |
Warning Signs of Wrong Code
| Sign | What It Means |
|---|
| Sudden pay decrease | Code may have changed incorrectly |
| Tax code letter is 0T | No allowances — check why |
| W1 or M1 suffix | Emergency code — needs sorting |
| K code unexpectedly | May be wrong |
| Different to colleagues (same job) | One of you is wrong |
Common Tax Code Errors
Error 1: Benefits Not Removed
| Problem | Effect |
|---|
| Left old job with company car | Still taxed as if you have it |
| Private healthcare ended | Still reducing your allowance |
| Fix | Report change to HMRC immediately |
Error 2: Two Jobs, Wrong Allocation
| Problem | Effect |
|---|
| Both jobs have BR code | Overpaying tax |
| Personal Allowance split wrong | Could be overpaying |
| Changed main job, code not updated | Wrong allocation |
| Fix | Update HMRC which is your main job |
Error 3: Marriage Allowance Not Applied
| Problem | Effect |
|---|
| Applied but not on code | Missing £252/year |
| Applied to wrong partner | No benefit |
| Fix | Check gov.uk/marriage-allowance |
Error 4: Emergency Tax Code
| Problem | Effect |
|---|
| New job, emergency code | May overtax initially |
| Shows W1/M1/X suffix | Non-cumulative calculation |
| Fix | Provide P45 or complete starter checklist |
Error 5: Wrong Address (Scotland/Wales)
| Problem | Effect |
|---|
| HMRC thinks you’re in Scotland | S code applied |
| Scottish rates different | May be wrong tax |
| Fix | Update address with HMRC |
How to Check Your Tax Code
Method 1: Personal Tax Account
| Step | Action |
|---|
| 1 | Go to gov.uk/personal-tax-account |
| 2 | Sign in with Government Gateway |
| 3 | View your tax code |
| 4 | See what’s included in calculation |
| 5 | Report if incorrect |
Method 2: Check Your Payslip
| Look For | Should Show |
|---|
| Tax code | Your current code |
| Tax paid this period | Amount deducted |
| Tax paid year to date | Cumulative |
| NI paid | Separate line |
Method 3: P60 (End of Year)
| Document | Shows |
|---|
| P60 | Annual earnings and tax paid |
| Available | After April 5 |
| Keep | For 22 months minimum |
Getting Refunds
How Much Could You Be Owed?
| Error Type | Typical Overpayment |
|---|
| Wrong code for 1 year | £500-2,000 |
| Wrong code for 4 years | £2,000-8,000 |
| Emergency tax on new job | £100-500 |
| Old benefits still on code | £500-2,000 |
Claiming Back Overpaid Tax
| Method | When to Use |
|---|
| Automatic refund | HMRC updates code mid-year |
| P800 letter | HMRC sends after year-end |
| Form P87 | Simple expense claims |
| Self Assessment | Complex situations |
Timeline for Refunds
| Claim For | Deadline |
|---|
| 2025/26 | April 2030 |
| 2024/25 | April 2029 |
| 2023/24 | April 2028 |
| 2022/23 | April 2027 |
You can claim refunds for the previous 4 complete tax years.
What Affects Your Tax Code
Things That Reduce Your Allowance
| Factor | Effect on Code |
|---|
| Company car | Lower number |
| Private medical insurance | Lower number |
| Living accommodation | Lower number |
| Income over £100k | Lose allowance |
| Underpaid tax from previous year | Lower number |
| State Pension | Lower number (if employed too) |
Things That Increase Your Allowance
| Factor | Effect on Code |
|---|
| Marriage Allowance received | Higher number (M suffix) |
| Blind person’s allowance | Higher number |
| Job expenses (if claimed) | Higher number |
Income Over £100,000
| Income | Personal Allowance | Code |
|---|
| £100,000 | £12,570 | 1257L |
| £110,000 | £7,570 | 757L |
| £120,000 | £2,570 | 257L |
| £125,140+ | £0 | 0T |
Lose £1 of allowance for every £2 over £100,000.
Special Situations
Multiple Jobs
| Approach | How It Works |
|---|
| Full allowance on main job | 1257L |
| No allowance on second job | BR or D0 |
| Split allowance | Partial on each |
State Pension + Employed
| How It Works | |
|---|
| State Pension uses some allowance | Reduces your code |
| Example: £9,000 State Pension | Code might be 357L |
| You effectively pay tax on State Pension | Via your employment |
Company Car
| Car List Price | CO2 Impact | Rough Allowance Reduction |
|---|
| £30,000 | Medium | ~£8,000 from allowance |
| £30,000 | Electric (3%) | ~£900 from allowance |
Electric cars have minimal impact on your tax code.
Taking Action
If Your Code Is Wrong
| Step | Timeframe |
|---|
| Check Personal Tax Account | Now |
| Gather evidence (payslips, P60) | Before contacting |
| Call HMRC (0300 200 3300) | Allow 30+ mins |
| Or update online | Usually quicker |
| Wait for new coding notice | 2-6 weeks |
| Check refund arrives | Next paycheck or P800 |
What to Tell HMRC
| Information Needed | Why |
|---|
| Your NI number | Identifies you |
| Current tax code | What you’re querying |
| What’s wrong | Specific issue |
| Evidence | P45, payslips, etc. |
Key Takeaways
- 1257L is standard — most people should have this
- Check annually — codes can go wrong any time
- Use Personal Tax Account — easiest way to check
- Report changes — company car, job change, etc.
- Claim refunds — up to 4 years back
- £100k+ income — expect reduced allowance
For related content, see our take-home pay calculator, marriage allowance guide, and income tax guide.