UK Tax Codes Explained 2025/26 - What Every Code Means and How to Fix a Wrong One
Quick Summary: 40 million UK workers have a tax code on their payslip. Most have never looked at it. But a wrong tax code can mean overpaying hundreds of pounds per year — or quietly building up a tax debt you don’t know about. This guide decodes every code, explains exactly what each letter and number means, and tells you precisely how to fix it if something’s wrong.
Table of Contents
- What Is a Tax Code and Why Does It Matter?
- How to Read Your Tax Code: Numbers and Letters Explained
- The Most Common Tax Code: 1257L
- Tax Code Letters: Every Single One Explained
- Emergency Tax Codes: W1, M1, and X
- The K Code: When HMRC Owes More Than You Earn
- Second Job Tax Codes: BR, D0, D1
- Marriage Allowance Tax Codes: M and N
- Scottish Tax Codes: S Prefix
- Welsh Tax Codes: C Prefix
- How HMRC Sets Your Tax Code
- How to Check If Your Tax Code Is Wrong
- How to Fix a Wrong Tax Code
- Tax Code and Savings Interest Adjustments
- Frequently Asked Questions
1. What Is a Tax Code and Why Does It Matter? {#what-is}
Your tax code is a short combination of numbers and letters — like 1257L or BR or K475 — that HMRC sends to your employer or pension provider. It tells them exactly how much income tax to deduct from each pay packet.
It looks technical. It isn’t. Once you understand the structure, you can read any tax code in under 30 seconds and instantly know whether you’re paying the right amount of tax.
Why it matters:
A wrong tax code costs real money. If your code is too low (giving you too small a tax-free allowance), you overpay tax every month — silently losing money you’re entitled to keep. If your code is too high, you underpay during the year and face a demand letter from HMRC after the year ends.
┌──────────────────────────────────────────────────────────────────┐│ COST OF A WRONG TAX CODE: EXAMPLES ││ ││ Error Type Salary Monthly Overpay Annual ││ ────────────────────────────────────────────────────────────── ││ Code 1100L instead 1257L £35,000 £26/month £312/year ││ Code BR instead 1257L £25,000 £209/month £2,514/yr ││ Code 1050L instead 1257L £45,000 £41/month £494/year ││ Emergency code M1 £30,000 Varies monthly Up to £800 ││ ││ HMRC estimates over 5 million people have incorrect codes ││ at any given time. Most never notice. │└──────────────────────────────────────────────────────────────────┘
💡 Related reading: How to File Self Assessment 2025/26 · Am I Owed an HMRC Tax Refund?
2. How to Read Your Tax Code: Numbers and Letters Explained {#how-to-read}
Every standard UK tax code has two components: a number and one or more letters.
The Number
The number tells your employer how much income you can earn from that source tax-free, per year. To get the actual amount, multiply the number by 10.
┌──────────────────────────────────────────────────────────────────┐│ TAX CODE NUMBER → TAX-FREE ALLOWANCE ││ ││ Code Number × 10 Tax-Free Allowance ││ ────────────────────────────────────────────────────────────── ││ 1257 × 10 £12,570 (standard personal allowance) ││ 1383 × 10 £13,830 (+ marriage allowance received) ││ 1131 × 10 £11,310 (- marriage allowance given) ││ 1207 × 10 £12,070 (- some adjustment/benefit) ││ 1100 × 10 £11,000 (- larger adjustment) ││ 500 × 10 £5,000 (significantly reduced) ││ 0T × 0 £0 (no personal allowance) │└──────────────────────────────────────────────────────────────────┘
When HMRC adjusts your code — for savings interest, a company car, an underpayment from last year — they change this number up or down. The bigger the number, the less tax you pay each month. The smaller the number, the more tax you pay.
The Letter(s)
The letter(s) after the number tell your employer about special circumstances affecting your tax. This is where most of the complexity lies.
3. The Most Common Tax Code: 1257L {#1257L}
1257L is the standard tax code for 2025/26 (and 2026/27 — the personal allowance has been frozen at £12,570 until April 2028).
- 1257 = £12,570 personal allowance (÷ 10)
- L = entitled to the standard tax-free personal allowance
If you have one job, no company car or other benefits in kind, and no unusual income sources, this should be your code. Around 30 million UK workers currently have 1257L.
What 1257L means for your pay:
┌──────────────────────────────────────────────────────────────────┐│ HOW 1257L WORKS ON YOUR PAYSLIP (MONTHLY PAY) ││ ││ Annual salary: £30,000 ││ Monthly pay: £2,500 ││ Monthly tax-free allowance: £12,570 ÷ 12 = £1,047.50 ││ Taxable monthly income: £2,500 - £1,047.50 = £1,452.50 ││ Monthly income tax at 20%: £1,452.50 × 20% = £290.50 ││ Monthly NI (Class 1): ~£148 ││ Monthly take-home (approx): £2,500 - £290.50 - £148 = £2,062 ││ ││ Annual income tax paid: £290.50 × 12 = £3,486 │└──────────────────────────────────────────────────────────────────┘
The code works cumulatively — meaning your employer considers your total earnings and total tax paid so far in the tax year when calculating each month’s deduction. This automatically corrects small over- or underpayments as the year progresses.
4. Tax Code Letters: Every Single One Explained {#letters}
┌──────────────────────────────────────────────────────────────────┐│ TAX CODE LETTERS: COMPLETE GUIDE ││ ││ Letter Meaning ││ ────────────────────────────────────────────────────────────── ││ L Standard personal allowance. Most common. ││ M Marriage Allowance RECEIVED. Your code is higher. ││ N Marriage Allowance GIVEN AWAY. Your code is lower. ││ T HMRC needs to review your code (complex situation). ││ 0T Zero personal allowance (no tax-free amount). ││ BR All income taxed at Basic Rate (20%). ││ D0 All income taxed at Higher Rate (40%). ││ D1 All income taxed at Additional Rate (45%). ││ NT No Tax — income not taxed at source. ││ K Negative allowance (you owe extra; see section 6). ││ S Scottish taxpayer (prefix, not suffix). ││ C Welsh taxpayer (prefix, not suffix). ││ ││ Suffixes (after main code): ││ W1 Emergency: Week 1 basis (non-cumulative weekly). ││ M1 Emergency: Month 1 basis (non-cumulative monthly). ││ X Emergency: Non-cumulative (period not specified). │└──────────────────────────────────────────────────────────────────┘
L — Standard Allowance
You’re entitled to the full personal allowance with no special adjustments. The most common letter by far.
M — Marriage Allowance Received
Your partner has transferred £1,260 of their personal allowance to you. Your tax code number is higher than 1257 (typically 1383M — reflecting £13,830 of tax-free income). You pay about £21/month less tax. See our full guide: Marriage Allowance: How to Claim Up to £1,260.
N — Marriage Allowance Given
You’ve transferred £1,260 of your personal allowance to your partner. Your code number is lower than 1257 (typically 1131N). You pay slightly more tax, but as a couple you’re better off overall.
T — Complex Situation
HMRC uses the T suffix when your tax situation is complex enough that they need to manually calculate your code — for example, if you have multiple income sources, specific deductions, or adjustments that don’t fit other categories. Check your HMRC Personal Tax Account to see what’s included.
0T — Zero Personal Allowance
You receive no tax-free personal allowance from this income source. This happens when:
- You’ve used your entire personal allowance against another income source
- You started a new job without providing a P45 or completing a Starter Checklist
- Your income exceeds £125,140 (personal allowance is fully tapered away)
- HMRC has applied your entire allowance to offset deductions/benefits
With 0T, you pay 20% tax from the very first pound of income from this source.
BR — Basic Rate
All income from this source is taxed at 20% flat, with no personal allowance applied. Common for:
- Second jobs (your first job uses your full personal allowance)
- Pensions (if your main pension/employment already uses the allowance)
With BR code on a £10,000 second income: you pay £2,000 in tax. Compare to 1257L where you’d pay nothing (within the allowance).
D0 — Higher Rate
All income taxed at 40%. Used for additional income sources where you’re already a higher-rate taxpayer and your allowance is fully allocated elsewhere.
D1 — Additional Rate
All income taxed at 45%. For additional income sources when you’re already an additional-rate (£125,140+) taxpayer.
NT — No Tax
No income tax deducted at source. Used for specific exempt payments or non-taxable income streams.
5. Emergency Tax Codes: W1, M1, and X {#emergency}
Emergency tax codes are temporary codes HMRC applies when they don’t have enough information about your income to issue the correct code — most commonly when you start a new job.
The three emergency code suffixes:
- W1 — Week 1 basis. Each week is taxed in isolation, ignoring prior weeks in the tax year.
- M1 — Month 1 basis. Each month is taxed in isolation, ignoring prior months.
- X — Non-cumulative, period unspecified.
Why emergency tax usually means overpaying:
Standard cumulative codes spread your personal allowance evenly across the year. Emergency codes treat each pay period as if it’s the first — giving you only 1/52 (weekly) or 1/12 (monthly) of your annual allowance per period.
┌──────────────────────────────────────────────────────────────────┐│ EMERGENCY TAX vs CORRECT CODE: REAL DIFFERENCE ││ ││ Scenario: New job in December, £3,000/month salary ││ It's month 9 of the tax year ││ ││ EMERGENCY CODE (1257L M1): ││ Monthly allowance: £12,570 ÷ 12 = £1,047.50 ││ Taxable: £3,000 - £1,047.50 = £1,952.50 ││ Monthly tax: £1,952.50 × 20% = £390.50 ││ ││ CORRECT CUMULATIVE CODE (1257L): ││ Year-to-date allowance: £1,047.50 × 9 = £9,427.50 ││ Prior earnings: £0 (new job) ││ Unused allowance: £9,427.50 ││ Taxable: £3,000 - £9,427.50 = £0 (covered by allowance) ││ Monthly tax: £0 ││ ││ Overpayment on emergency code: £390.50 that month ││ Refunded automatically when code is corrected │└──────────────────────────────────────────────────────────────────┘
How to fix emergency tax:
Provide your P45 from your previous employer to your new employer as soon as possible. The P45 tells HMRC your income and tax paid so far in the year — enabling them to issue the correct cumulative code.
Complete the Starter Checklist (formerly P46) if you don’t have a P45. Choose the correct statement:
- Statement A: This is your only job this tax year (first job of the year, or returning after a break)
- Statement B: You have another job or receive a pension
- Statement C: You have another job AND/OR received Jobseeker’s Allowance/ESA this tax year
Wait for HMRC to update your code. Once they have the correct information, they issue a new coding notice to your employer. Any overpaid tax is automatically refunded through your next payslip(s).
Don’t wait too long. If your code isn’t corrected after 4–6 weeks, contact HMRC on 0300 200 3300 with your employer’s PAYE reference and your NI number.
6. The K Code: When HMRC Owes More Than You Earn {#k-code}
The K code is the most confusing tax code for most people — and for good reason, because it works backwards from everything else.
When a K code is issued:
HMRC issues a K code when the total of your deductions (things that reduce your tax-free amount) exceeds your personal allowance. This usually happens when:
- You have significant company benefits in kind (expensive company car, private medical insurance, living accommodation)
- You have tax underpaid from a previous year being collected through your current code
- You receive a state pension that exceeds your personal allowance (common for pensioners with multiple income sources)
How the K code works:
Instead of reducing your taxable income by your allowance, a K code adds a notional amount to your income before calculating tax. The number after K (e.g., K450) represents the addition amount × 10.
┌──────────────────────────────────────────────────────────────────┐│ K CODE: HOW IT WORKS IN PRACTICE ││ ││ Example: Tax code K450, salary £30,000 ││ ││ K450 means: Add £4,500 (450 × 10) to your taxable income ││ Personal allowance: £12,570 ││ Company car benefit: £17,070 ││ Deductions exceed allowance by: £17,070 - £12,570 = £4,500 ││ → K450 ││ ││ Calculation: ││ Salary: £30,000 ││ + K addition: +£4,500 ││ = Notional taxable income: £34,500 ││ Tax at 20%: £6,900 ││ Effective rate on actual salary: 23% ││ ││ vs 1257L code: ││ Taxable: £30,000 - £12,570 = £17,430 ││ Tax: £3,486 ││ ││ Difference: £3,414/year extra tax under K450 │└──────────────────────────────────────────────────────────────────┘
The K code cap:
There’s a legal limit to how much tax can be deducted in any single pay period under a K code: no more than 50% of your gross pay for that period. This protects people from having their entire salary wiped out by tax.
What to do if you have a K code:
- Check your HMRC Personal Tax Account to see exactly what is included in your K code calculation
- Verify your employer has reported your benefits correctly on the P11D
- Check if any previous year’s underpayment being collected is correct
- If you dispute the inclusion, contact HMRC on 0300 200 3300
7. Second Job Tax Codes: BR, D0, D1 {#second-job}
When you have two jobs simultaneously, each pays you separately — but you only get one personal allowance across all your income combined.
Standard approach:
- First job / main income: Gets your full personal allowance (code 1257L)
- Second job: Gets BR (all at 20%), D0 (all at 40%), or D1 (all at 45%) depending on which tax band your second income falls into
┌──────────────────────────────────────────────────────────────────┐│ SECOND JOB TAX CODES: WHICH APPLIES? ││ ││ First Job Income Second Job Band Second Job Code ││ ────────────────────────────────────────────────────────────── ││ Under £50,270 Basic rate (20%) BR ││ £50,271+ Higher rate (40%) D0 ││ £125,140+ Additional (45%) D1 ││ ││ Example: First job £35,000, Second job £8,000 ││ Second job code: BR (all at 20%) ││ Second job tax: £8,000 × 20% = £1,600 ││ ││ Example: First job £55,000, Second job £10,000 ││ Second job code: D0 (all at 40%) ││ Second job tax: £10,000 × 40% = £4,000 │└──────────────────────────────────────────────────────────────────┘
Splitting your allowance between jobs:
If your second job is steady and significant, you can ask HMRC to split your personal allowance between employers — reducing the tax on your second income. Contact HMRC on 0300 200 3300 or do it through your Personal Tax Account. This only makes sense if the total of both incomes stays within the basic-rate band.
8. Marriage Allowance Tax Codes: M and N {#marriage}
When the Marriage Allowance is active:
- The receiving partner gets the M suffix and a higher code number (1383M = £13,830 tax-free)
- The giving partner gets the N suffix and a lower code number (1131N = £11,310 tax-free)
The M code saves the receiving partner approximately £252/year (£1,260 × 20%). The N code costs the giving partner nothing — they weren’t using that £1,260 of allowance anyway (since they earn under £12,570).
See our full guide: Marriage Allowance: How to Claim Up to £1,260
9. Scottish Tax Codes: S Prefix {#scottish}
If you live in Scotland, your tax code starts with S (e.g., S1257L, SBR, SD0). This tells your employer to apply Scottish income tax rates and bands rather than the UK-wide (rUK) rates.
┌──────────────────────────────────────────────────────────────────┐│ SCOTTISH vs rUK INCOME TAX RATES 2025/26 ││ ││ Band Scottish Rate rUK Rate Difference ││ ────────────────────────────────────────────────────────────── ││ Starter (to £14,876) 19% 20% -1% ││ Basic (to £26,561) 20% 20% 0% ││ Intermediate(to£43,662)21% 20% +1% ││ Higher (to £75,000) 42% 40% +2% ││ Advanced (to £125,140) 45% 40% +5% ││ Top rate (over £125,140) 48% 45% +3% ││ ││ Scottish taxpayers pay more on incomes above ~£28,000 ││ and fractionally less on incomes below ~£14,876 ││ ││ Note: Savings interest is still taxed using rUK bands ││ regardless of where in the UK you live │└──────────────────────────────────────────────────────────────────┘
Important: If you move to or from Scotland, update your address with HMRC immediately so your tax code reflects the correct rates.
10. Welsh Tax Codes: C Prefix {#welsh}
Welsh taxpayers have tax codes prefixed with C (e.g., C1257L). Wales has the power to vary income tax rates but has chosen to mirror the England/Northern Ireland rates for 2025/26 — so Welsh taxpayers pay the same rates as English taxpayers, just using the C prefix code.
11. How HMRC Sets Your Tax Code {#how-set}
HMRC builds your tax code from multiple data sources:
┌──────────────────────────────────────────────────────────────────┐│ HOW HMRC CALCULATES YOUR TAX CODE ││ ││ Start with: £12,570 (personal allowance) ││ ││ Add: ││ + Marriage allowance received +£1,260 ││ + Job expenses/reliefs +variable ││ + Pension contribution relief +variable ││ + Blind Person's Allowance +£3,070 ││ ││ Subtract: ││ - Marriage allowance given -£1,260 ││ - Company car/van benefit -variable ││ - Private medical insurance -variable ││ - Estimated savings interest -variable ││ - Underpaid tax from prior year -variable ││ - State benefits over allowance -variable ││ ││ Result ÷ 10 = code number + appropriate letter = your code │└──────────────────────────────────────────────────────────────────┘
Key data sources HMRC uses:
- Your employer’s RTI submissions — real-time payroll data sent each pay period
- Your P11D — annual benefits in kind report from your employer
- Bank data — annual interest reports from your bank
- Your Self Assessment return — prior year data
- DWP data — state pension, Jobseeker’s Allowance, other benefits
- Your Personal Tax Account updates — if you’ve told HMRC about changes
HMRC may estimate some figures (particularly savings interest and benefits) based on prior years. These estimates are often wrong — which is why your code needs checking.
12. How to Check If Your Tax Code Is Wrong {#check}
Step 1: Find your current tax code
- Look at your most recent payslip (shown as “Tax Code” or “Code”)
- Check your P60 at year end
- Log into your HMRC Personal Tax Account at gov.uk/personal-tax-account
- Check the HMRC app
Step 2: Verify what’s included
Log into your Personal Tax Account and go to “Income Tax” → “Check your Income Tax for the current year”. HMRC shows exactly what’s in your code — every adjustment, benefit, and allowance.
Step 3: Cross-check the common errors
┌──────────────────────────────────────────────────────────────────┐│ MOST COMMON TAX CODE ERRORS ││ ││ Error How to spot it ││ ────────────────────────────────────────────────────────────── ││ Old company car still in code Left company but code unchanged ││ Savings interest overestimated Code lower than expected ││ Pension not accounted for Code lower than expected ││ Benefits from old job included Changed jobs but code similar ││ Emergency code not updated W1/M1 suffix after first month ││ Wrong marriage allowance M or N suffix but not applied ││ Prior year debt wrong amount K code with unexpected number ││ Scottish/Welsh prefix missing Moved to/from Scotland/Wales │└──────────────────────────────────────────────────────────────────┘
Step 4: Calculate the cost of the error
If your code is too low by X (e.g., HMRC has your code as 1150L instead of 1257L — a difference of 107):
- Allowance gap: 107 × 10 = £1,070 less tax-free income
- Annual overpayment at 20%: £1,070 × 20% = £214/year
- Monthly overpayment: £17.80/month quietly disappearing from your payslip
13. How to Fix a Wrong Tax Code {#fix}
You have several ways to update your tax code:
Fastest: HMRC Personal Tax Account (online)
- Go to gov.uk/personal-tax-account
- Sign in to Government Gateway
- Navigate to “Income Tax” → “Check your Income Tax”
- Review what’s in your code and update any incorrect items
- HMRC updates your code and issues a P2 notice to your employer within a few weeks
By phone: Call HMRC’s income tax helpline: 0300 200 3300 (Mon–Fri, 8am–6pm) Have your: NI number, employer’s PAYE reference, P60 or payslip, details of the error
What happens after you report the error:
- HMRC issues a new P2 PAYE Coding Notice
- Your employer applies the new code from the next available pay run
- If you overpaid, the refund is built into your subsequent payslips automatically (your tax deductions reduce to compensate)
- Large overpayments may warrant a direct claim — see Am I Owed an HMRC Tax Refund?
Can your employer change your code without HMRC?
No. Employers are legally prohibited from changing your tax code without an instruction from HMRC. If you tell your employer your code is wrong, they can note it but cannot act until HMRC issues a new coding notice. Always go direct to HMRC.
14. Tax Code and Savings Interest Adjustments {#savings}
Since 2016, HMRC has been adjusting tax codes to collect savings tax — reducing your personal allowance by the amount of savings interest you’re expected to earn above your Personal Savings Allowance.
How it works:
If HMRC believes you’ll earn £800 of taxable savings interest this year (above your PSA), they reduce your tax code by 80 — changing 1257L to 1177L.
┌──────────────────────────────────────────────────────────────────┐│ SAVINGS INTEREST TAX CODE ADJUSTMENTS ││ ││ Savings interest expected: £1,800 ││ PSA (basic rate taxpayer): -£1,000 ││ Taxable interest: £800 ││ ││ Code adjustment: 800 ÷ 10 = 80 ││ New code: 1257L - 80 = 1177L ││ ││ Effect: £800 less tax-free income ││ Extra tax collected: £800 × 20% = £160/year ││ Spread across payslips: £13.33/month more tax ││ ││ If you moved money to an ISA and interest will be lower: ││ Call HMRC to update the estimate and restore your code number │└──────────────────────────────────────────────────────────────────┘
Common problem: HMRC uses previous year’s savings interest to estimate the current year. If you’ve moved money to an ISA, switched accounts, or savings rates have changed, the estimate may be wrong. Call HMRC with your current savings account details and approximate interest to get the code corrected.
See our full guide: HMRC Savings Tax Bills: The Complete Guide
15. Frequently Asked Questions {#faq}
What is the tax code for 2025/26?
The standard tax code for 2025/26 is 1257L — the same as 2024/25. The personal allowance of £12,570 is frozen until April 2028.
Why has my tax code changed?
HMRC changes codes when: your income changes, you start or stop receiving benefits, your savings interest increases, you have an underpayment from a prior year, or you start or stop claiming Marriage Allowance. You’ll receive a P2 PAYE Coding Notice explaining the change.
My code has gone down — will I get a refund?
If your code has gone down (giving you less tax-free income), you’re paying more tax each month. If this was applied incorrectly, contact HMRC, get it corrected, and the overpayment will be refunded through future payslips. See Am I Owed an HMRC Tax Refund?.
What is the difference between 1257L W1 and 1257L?
Both give the same £12,570 annual allowance, but the W1 suffix means it’s applied on a non-cumulative week-1 basis — each week is treated independently. Standard 1257L is cumulative, accounting for all prior weeks/months in the tax year. The W1 suffix typically means you’re on emergency tax and may be overpaying.
I have two jobs. Do I get two personal allowances?
No. You get one personal allowance across all income sources. HMRC allocates it to your primary job. Your second job will be coded BR, D0, or D1.
My code contains letters I don’t recognise. What should I do?
Log into your HMRC Personal Tax Account to see a full breakdown of your code. If anything looks wrong, call HMRC on 0300 200 3300.
Tax Codes Quick Reference
┌──────────────────────────────────────────────────────────────────┐│ TAX CODES QUICK REFERENCE 2025/26 ││ ││ Your code What it means Action needed? ││ ────────────────────────────────────────────────────────────── ││ 1257L Standard. Correct for most. None if single job ││ 1383M Marriage allowance received Check partner gave ││ 1131N Marriage allowance given Check partner got ││ BR No allowance this source Normal 2nd job ││ D0 All at 40% this source Normal 2nd job ││ D1 All at 45% this source Normal high earner ││ 0T Zero allowance Check reason ││ K[number] Negative allowance Check what's in it ││ [code]W1/M1 Emergency tax Provide P45 ASAP ││ NT No tax deducted Check reason ││ S[code] Scottish taxpayer Correct if Scottish ││ C[code] Welsh taxpayer Correct if Welsh ││ T Complex — HMRC review Check PTA details │└──────────────────────────────────────────────────────────────────┘
Information correct as of May 2026. Always verify at gov.uk. This article does not constitute personal tax advice.
Internal Links:
- HMRC Savings Tax Bills 2025/26
- Am I Owed an HMRC Tax Refund?
- Marriage Allowance: How to Claim Up to £1,260
- How to File Self Assessment 2025/26
- HMRC Penalties: How They Work and How to Appeal
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