The UK's most complete tax-code decoder
UK Tax Code Checker
Decode any HMRC tax code in plain English. Add your salary, pension, and student loan plan to see exact tax, NI and take-home — broken down per pay period and visualised by tax band. Multi-year (2024/25, 2025/26, 2026/27), UK + Scotland + Wales.
Quick decode
Advanced — pension, student loan, salary sacrifice
1257L
Valid · England/Wales/NI rates · 2026/27
Personal Allowance of £12,570 per year. Standard Personal Allowance entitlement.
Personal Allowance: £12,570
What if I take a second job? →
Want an AI check on your actual payslip?
Snap your payslip — full AI analysis →UK Tax Code Letters & Prefixes — full reference
| Letter | Type | Meaning |
|---|---|---|
| L | Suffix | Standard tax-free Personal Allowance |
| M | Suffix | Marriage Allowance recipient (10% of partner allowance transferred to you) |
| N | Suffix | Marriage Allowance transferor (you transferred 10% to your partner) |
| T | Suffix | HMRC needs to review your tax code |
| S | Prefix | Scottish Income Tax rates apply |
| C | Prefix | Welsh Income Tax rates apply |
| K | Prefix | Income not taxed another way exceeds your allowances |
| BR | Special | All income taxed at basic rate (20%) |
| D0 | Special | All income taxed at higher rate (40%) |
| D1 | Special | All income taxed at additional rate (45%) |
| NT | Special | No tax deducted |
| 0T | Special | No Personal Allowance — all income taxed through bands |
| W1 / M1 / X | Modifier | Emergency / non-cumulative — each pay period taxed independently |
FAQs
What does my tax code mean?
The number × 10 = your tax-free Personal Allowance. The letters tell your employer which rates and adjustments to apply.
What is the most common UK tax code?
1257L — used by ~85% of UK taxpayers. Reflects the 2026/27 standard Personal Allowance of £12,570.
What is an emergency tax code?
W1, M1, or X means HMRC are taxing each pay period independently — usually due to a missing P45. Most resolve within 1-2 payslips, but unresolved emergency codes are a major source of overpayment.
Why has my tax code changed?
From April 2026 HMRC Dynamic Coding pushes new codes mid-year — new job, second job, company-car benefit added or removed, Marriage Allowance, untaxed interest projected. See the P2 letter decoder →
Sources
- • GOV.UK — Tax codes
- • GOV.UK — Income Tax rates and Personal Allowances
- • GOV.UK — Check your Income Tax
- • GOV.UK — Marriage Allowance
Disclaimer: Estimates use UK tax bands and NI rates for the selected year. Educational guidance only — your actual deductions depend on full circumstances. Always verify on your HMRC personal tax account or with a qualified adviser before making decisions.