Tax Code Checker
Updated November 2026 · Free · No sign-up
Check what your UK tax code means — decode 1257L, BR, D0, K codes, W1/M1 emergency markers, and see whether your code is costing you money every payday.
Quick answer: The numbers × 10 = your tax-free allowance (1257L = £12,570); the letters set the rules. BR taxes everything at 20%, D0 at 40%, K codes mean negative allowance, W1/M1 means emergency non-cumulative. A wrong code quietly over- or under-taxes you until fixed.
Decoding the Parts
| Code element | Meaning |
|---|---|
| Numbers (1257) | Tax-free allowance ÷ 10 — 1257 = £12,570 standard personal allowance |
| L | Standard allowance |
| M / N | Marriage Allowance received (+10%) / given (−10%) |
| BR | ALL income at 20% — normal for second jobs; wrong for your main job |
| D0 / D1 | All at 40% / 45% — second jobs for higher earners |
| K (K475) | NEGATIVE allowance — untaxed benefits/debts exceed the allowance; K475 ADDS £4,750 to taxable pay |
| 0T | No allowance, banded rates — missing starter info |
| NT | No tax (rare, specific situations) |
| W1/M1/X | Emergency non-cumulative: each period taxed in isolation, no year-to-date correction |
| S / C prefix | Scottish / Welsh rates apply |
Worked Examples
Example 1 — BR on a main job. £38,000 salary on BR: no personal allowance applied → overpaying ~£2,514/year (£12,570 × 20%). Classic after job switches with lost P45s — fix via HMRC app, refund follows through payroll.
Example 2 — K code. K475: £4,750 is ADDED to taxable pay (company car, unpaid tax collection). Not an error by default — but check the benefit values behind it in your PAYE account.
Example 3 — 1257L W1 after a job change. Non-cumulative basis ignores earlier-year overpayments — fine mid-year, money back when the code normalizes; see the emergency tax calculator for the refund math.
Why Codes Go Wrong (The Usual Suspects)
- Job changes without P45 → emergency/0T/BR codes until HMRC catches up.
- Two jobs or pension + job: the allowance belongs on the LARGER income; many people leave it on a small pension and bleed 20% unnecessarily on the job.
- Benefits in kind: company car/medical adjust the number down (or into K) — stale benefit values linger for years after you return the car.
- Untracked allowances: Marriage Allowance, uniform/professional fees, and working-from-home claims raise the number — unclaimed, they expire after 4 years.
Fixing a Wrong Code
Check your PAYE income sources in the HMRC app/personal tax account, correct the estimated income figures, and the new code flows to payroll in days — cumulative codes then auto-refund overpayments in the next pay run. Refunds for PREVIOUS years come via P800 letters or claims (4-year window). A wrong code changes withholding, never the true tax — but cash-flow-wise, that's cold comfort in the months you're overpaying; the umbrella and salary pages here all assume 1257L.
Frequently Asked Questions
What does tax code 1257L mean?
The standard code: £12,570 of tax-free personal allowance (1257 × 10), spread across the year, with normal banded rates above it.
Why is my tax code BR?
Everything taxed at 20% with no allowance — correct for second jobs, wrong for your only/main job (commonly after a job change without a P45). Fixing it refunds automatically.
What is a K tax code?
Negative allowance: untaxed benefits or owed tax exceed your personal allowance, so K-number × 10 is ADDED to taxable pay. Verify the benefit values behind it.
What does W1 or M1 mean?
Emergency non-cumulative basis — each payday taxed in isolation without year-to-date correction. Normal after job changes; refunds flow when the cumulative code arrives.
How do I change my tax code?
Update income/benefit estimates in your HMRC personal tax account or app — codes reissue within days and payroll applies them with automatic in-year refunds.
Can I reclaim tax from previous years?
Yes — four tax years back, via P800 reconciliations or an overpayment claim to HMRC.
✓ Formula verified • Last updated: November 3, 2026