Tool
Tax Code Checker
Decode your UK tax code in seconds. Wrong codes are common — costs you tax all year if not corrected.
Your code
Wrong tax code costing you money?
We can check yours and get HMRC to correct it as part of any Self Assessment filing — from £79.
What is a tax code?
Your tax code tells your employer how much income tax to deduct from each pay packet via PAYE. It's a combination of numbers (your tax-free Personal Allowance ÷ 10) and letters (modifiers explaining your situation).
Standard 2025/26 code: 1257L. The "1257" means £12,570 PA; the "L" is the standard suffix for "you get the full PA".
Common tax codes decoded
| Code | Meaning |
|---|---|
| 1257L | Standard — full PA, normal employee |
| BR | Basic rate — all income taxed at 20%, no PA (usually a 2nd job) |
| D0 | Higher rate — all income taxed at 40% |
| D1 | Additional rate — all income at 45% |
| NT | No tax |
| 0T | No PA, can't be M1/W1 (often emergency) |
| K (e.g. K500) | Negative — your taxable benefits exceed PA |
| M / N suffix | Marriage Allowance received / transferred |
| S prefix | Scottish taxpayer (different bands) |
| C prefix | Welsh taxpayer |
Why your tax code might be wrong
- Started a new job and the previous P45 wasn't passed on
- You took on a second job and BR wasn't applied correctly
- HMRC adjusted for previous-year underpayment without your knowledge
- A taxable benefit (company car, private health) was added/removed
- You started/stopped receiving a state pension
- You moved to / from Scotland or Wales
How to fix a wrong tax code
- Personal Tax Account at gov.uk — view and update online
- HMRC helpline 0300 200 3300 — explain the situation, they often correct on the call
- P87 form — claim back overpaid tax for past years
- Self Assessment — if you also need to file SA, the wrong code gets reconciled automatically
Calculation notes
What this calculator does and doesn't do
- Number × 10 = your annual Personal Allowance (e.g. 1257 → £12,570)
- L = standard suffix · M = received Marriage Allowance · N = transferred to spouse · T = other adjustments · K = negative (BIKs exceed PA)
- BR = basic rate (20%) on all · D0 = higher (40%) · D1 = additional (45%) · NT = no tax · 0T = no PA, no M1/W1
- If your code looks wrong, contact HMRC or get us to file a correction
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