Your UK tax code determines how much Income Tax is deducted from your pay via PAYE. In 2026/27, the standard code is 1257L (£12,570 personal allowance). Different letters signal different circumstances: marriage allowance transfer, second job, taxable benefits, Scottish resident, allowance reduction. This guide decodes every letter, explains K codes (owing tax), and how to check + correct your code.
Verified against 2 official sources · Last reviewed 14 June 2026
Adjustments — HMRC needs review; often high income + taper
BR
Basic rate on all pay — usually second job or pension
D0
Higher rate on all pay — third income or high earnings
D1
Additional rate on all pay — top-rate on this source
NT
No Tax — usually specific pension or split treatment
0T
No allowance — emergency code + all pay taxed at bands
K
You owe tax — allowance reduced below zero (usually large BiK)
W1/M1/X
Emergency — non-cumulative; only current period
Scottish codes
Prefix S — Scottish rates apply.
- S1257L: Scottish standard code
- SBR: Scottish basic rate
- SD0: Scottish intermediate
- SD1: Scottish higher
- SD2: Scottish top
Welsh codes
Prefix C — Welsh rates apply (currently same as rUK).
K codes explained
When you owe tax (e.g. large BiK), HMRC adjusts your code below zero. K600 means £6,000 added to your taxable pay per year.
Emergency tax codes
Applied when you start a new job without P45 or HMRC has incomplete information. Common: 1257L W1/M1. Non-cumulative — each pay period taxed as if standalone.
How to check your code
Payslip: shown at top
HMRC personal tax account: gov.uk/personal-tax-account
P60/P45: shows code
P800: end of year reconciliation
How to fix an incorrect code
Check via HMRC personal tax account
Call HMRC 0300 200 3300 (payer's helpline)
Update via personal tax account online
Employer receives updated code via HMRC PAYE Coding Notice
In short
Your tax code decodes personal allowance + adjustments. Common issues: emergency codes on new jobs, K codes for BiK, second-job BR codes.
Frequently asked questions
Why did my tax code change mid-year?
Common triggers: new benefit added (car, medical), state pension started, marriage allowance change, HMRC recalculating estimated income.
What if my tax code is wrong?
Update via HMRC personal tax account. Overpaid tax refunded automatically via subsequent payroll or year-end P800. Underpaid amounts collected via code change.
Do I need to tell my employer if my tax code changes?
No — HMRC notifies employer directly via PAYE Coding Notice. Employer applies new code from next pay period.
Why am I on emergency tax?
Usually because you started a job without P45. Employer applies 1257L W1/M1 until HMRC provides correct code. Sort by giving employer P45 or completing New Starter Checklist.
Can I be on two tax codes?
Yes — one per income source. If you have 2 jobs, main job typically 1257L, second job BR. Update via HMRC personal tax account to split allowance if second job is main income.
All tax figures on this page use the same configuration that powers our
calculators — see our
editorial standards for the review process.
Last reviewed: 14 June 2026.
Next review due 14 December 2026.
Disclaimer: This page provides general information based on published HMRC and gov.scot figures. It is not personal tax or financial advice. For your specific situation, please consult a qualified accountant or contact HMRC directly.