Tax Code Checker UK
Decode your tax code and see if it’s right — because a wrong one quietly overpays your tax for months, or leaves you with a surprise bill at year end.
Your tax code is the short string on your payslip — usually 1257L — that tells your employer how much tax-free pay you get before Income Tax is deducted. The numbers are your tax-free allowance divided by 10 (1257 means £12,570), and the letters say what kind of taxpayer you are. Get it right and the tax taken across the year matches what you owe; get it wrong and you can overpay quietly for months or face a year-end bill. The part most people miss is the suffix: a code ending in W1, M1, or X is an emergency code that taxes each pay period in isolation, which usually over-deducts tax after a job change. Other codes flag specific situations — BR taxes everything at 20% (common on a second job), K codes work in reverse and add to your taxable pay, and an S or C prefix means Scottish or Welsh rates. This checker breaks your code into its parts, tells you what each means, and flags whether it looks right. To see the effect on your pay, use the Salary Take-Home Calculator; for couples, the Marriage Allowance Calculator.
Tax code details
Income estimate
Comparison settings
Situation checks
Tax code check result
Tax code meaning
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Estimated allowance
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Code type
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Standard code comparison
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Emergency flag
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Tax codes — quick lookup
The left table decodes the letters and whole-word codes you’ll see; the right covers the prefixes and emergency suffixes. The headline is in the right table: a suffix of W1, M1, or X means you’re on emergency tax and very likely overpaying — the part of your code most worth checking.
| Code | Meaning |
|---|---|
| L | Standard personal allowance (1257L) |
| M / N | Received / gave Marriage Allowance |
| K | Deductions exceed allowance (adds to pay) |
| BR / D0 / D1 | All income at 20% / 40% / 45% |
| 0T / NT | No allowance / no tax |
| Code | Meaning |
|---|---|
| S | Scottish income tax rates |
| C | Welsh income tax rates |
| W1 | Emergency, weekly, non-cumulative |
| M1 | Emergency, monthly, non-cumulative |
| X | Emergency, other pay periods |
A code’s number is your tax-free allowance divided by 10, so 1257L means £12,570 tax-free. M and N codes shift the number for Marriage Allowance (1383M, 1131N). K codes are negative: the number times 10 is added to your taxable pay rather than freed from tax. W1, M1, and X are added to a code (e.g. 1257L M1) and signal emergency, non-cumulative tax — usually an overpayment after a job change.
How tax codes work
A tax code looks cryptic, but it’s really just two pieces of information bolted together: how much you can earn tax-free, and any special circumstances that change how you’re taxed. Read it in those two parts and it stops being a mystery.
The number is your allowance ÷ 10
The digits in your code are your tax-free Personal Allowance divided by 10. The standard allowance is £12,570, so the standard code is 1257L — the most common code in the UK, used by around 85% of taxpayers. If your allowance is reduced or increased (by benefits, Marriage Allowance, or owed tax), the number changes to match. The Personal Allowance has been frozen at £12,570, so 1257L stays the default for anyone with one straightforward job.
The letter is your situation
The letter tells your employer what kind of taxpayer you are. L is the standard allowance. M means you’ve received Marriage Allowance from your partner; N means you’ve given yours away. K is the unusual one — it works in reverse, used when deductions (like a company car or owed tax) are bigger than your allowance, so the code adds to your taxable pay. Whole-word codes like BR (basic rate), D0 (higher rate), and D1 (additional rate) tax all your income at one flat rate, usually on a second job or pension.
The suffix that matters most: emergency codes
If your code ends in W1, M1, or X, you’re on an emergency, non-cumulative basis. Normally tax is worked out cumulatively — your allowance is spread evenly and your year-to-date earnings are taken into account. An emergency code instead taxes each pay period in isolation, as if it were the first of the year, ignoring any unused allowance from earlier months. This usually over-deducts tax after a job change, and the overpayment is refunded automatically once HMRC issues a proper cumulative code.
Worked examples
Four codes decoded — the standard, the emergency overpayment, the second-job code, and the reverse-working K code.
Example 1 · The standard code
1257L — nothing to worry about
Letter L = standard personal allowance
Verdict: correct for one straightforward job
This is the code around 85% of people see, and for most it’s exactly right. It gives the full £12,570 tax-free, then taxes the rest through the normal bands. If you have a single job, no taxable benefits, and no Marriage Allowance, 1257L is what you should expect. There’s nothing to fix — though it’s still worth confirming the number matches £12,570 and there’s no W1, M1, or X tacked on the end.
Example 2 · The emergency overpayment
1257L M1 — likely overpaying
M1 gives only 1/12 of allowance each month (£1,047.50)
Result: over-deducts tax until cumulative code arrives
Start a new job in, say, month seven without giving your employer a P45, and you may land on 1257L M1. Because it’s non-cumulative, it gives only one month’s slice of allowance rather than crediting the seven months you hadn’t used — so you over-deduct tax in the early payslips. Give your new employer your P45 or complete a Starter Checklist; HMRC then issues a cumulative code and the overpaid tax is refunded automatically.
Example 3 · The second-job code
BR — every pound at 20%
Second job coded BR: all of it taxed at 20%
Verdict: usually correct — but check if income is low
A BR code taxes all the income from that job at the basic rate, with no allowance, because your allowance is already used by your main job. This is normally correct for a second job. But if your total income is low and your main job doesn’t use all your allowance, you could ask HMRC to split your allowance between employers (for example 900L and 357L) to avoid over-withholding. If you’re already a higher-rate taxpayer, the second job may instead be coded D0 (40%).
Example 4 · The reverse code
K475 — adds to your taxable pay
K475 → £4,750 added to taxable income
Verdict: correct only if you have large untaxed benefits
A K code is the one that works backwards. Instead of giving tax-free pay, it adds an amount to your taxable income — here K475 adds £4,750 — because your taxable benefits or owed tax exceed your allowance. Common causes are a company car, medical insurance, or a State Pension alongside a job. K codes are legitimate, but worth checking: if the benefit no longer applies, the code should change, or you’ll keep overpaying.
Is your tax code wrong? Four things to check
A wrong code is one of the most common — and most quietly expensive — tax errors, because nothing alerts you; you just overpay or underpay until someone notices. Here’s how to tell if yours needs fixing, and what to do:
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1
Is there a W1, M1, or X on the end?
This is the first thing to look for. An emergency suffix means you’re taxed non-cumulatively and probably overpaying, usually after a job change. Hand your P45 or Starter Checklist to your employer; HMRC then issues a cumulative code and refunds the overpayment automatically.
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2
Does the number match your allowance?
For most people the number should be 1257 (£12,570). If it’s lower without reason — no benefits, no Marriage Allowance given away, no owed tax — your allowance may be wrongly reduced. If it’s a K code but you have no large benefits or untaxed income, that’s worth querying too.
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3
Do you have a second job or pension?
A second source coded BR, D0, or D1 is usually right, but check the rate fits your total income. If your main job doesn’t use all your allowance, you can ask HMRC to split the allowance between employers to stop over-withholding on the lower-paid job.
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4
Has your situation changed recently?
Codes lag reality. A new job, a benefit starting or ending, marriage, or a second income can all leave your code out of date. Only HMRC can change it — your employer can’t — so update your details through your Personal Tax Account or by contacting HMRC directly.
Same job, same pay — different codes, different tax
What the code does to your tax-free pay:
The same salary can produce wildly different monthly tax depending only on the code attached to it — which is why checking it is worth a couple of minutes. Most codes are correct, and 1257L on a single straightforward job rarely needs a second look. But after a job change, a new benefit, or starting a second income, the code is the thing most likely to be quietly wrong. If yours looks off, the fix is the same in every case: only HMRC can change it, so update your details through your Personal Tax Account or call them — your employer cannot adjust it on their own.
How to fix a wrong code
If you spot an emergency suffix, give your employer your P45 or complete a Starter Checklist, and the cumulative code (and any refund) follows automatically. For anything else — a wrong number, an outdated K code, a benefit that’s ended — contact HMRC through your Personal Tax Account at gov.uk or by phone. They’ll issue a corrected code to your employer. Overpaid tax within the year is usually refunded through your payslips; tax from earlier years is reclaimed separately. Your employer must use whatever code HMRC sends and can’t override it.
Two situations that confuse people
What if…
You started a new job and tax shot up?
What if…
Your code has an S or C in front?
Key tax code terms explained
A tax code packs several ideas into a short string — allowances, special rates, and how the year is calculated. The ten terms below cover what you’ll meet decoding yours.
- Tax code
- The short string on your payslip that tells your employer how much tax-free pay to give you before deducting Income Tax under PAYE. Made of numbers (your allowance) and letters (your situation).
- 1257L
- The standard code for most people: 1257 means £12,570 of tax-free Personal Allowance, and L means the standard allowance with no special circumstances. Used by around 85% of taxpayers.
- Personal Allowance
- The £12,570 you can earn tax-free each year. The number in your code is this allowance divided by 10. It has been frozen, so the standard code stays 1257L.
- Cumulative vs non-cumulative
- Cumulative codes spread your allowance evenly and count year-to-date earnings; non-cumulative (emergency) codes tax each pay period alone. The latter usually over-deduct after a job change.
- Emergency code (W1/M1/X)
- A temporary, non-cumulative code used when HMRC lacks full information, typically a new job without a P45. It usually overpays tax until a cumulative code replaces it, with the overpayment refunded automatically.
- K code
- A code that works in reverse: instead of tax-free pay, the number times 10 is added to your taxable income, used when deductions like a company car or owed tax exceed your allowance.
- BR, D0, D1
- Whole-word codes taxing all income at one flat rate — BR at 20%, D0 at 40%, D1 at 45% — with no allowance. Usually applied to a second job or pension where your allowance is used elsewhere.
- 0T and NT
- 0T gives no allowance, taxing every pound through the normal bands, often when HMRC has no starter information. NT means no tax is deducted at all, used in specific circumstances.
- S and C prefixes
- An S prefix means Scottish income tax rates, C means Welsh, based on where your main home is rather than where you work. The allowance is the same; the rates and bands differ.
- P45 and Starter Checklist
- The documents that tell HMRC your earnings and code when you change jobs. Handing over a P45, or completing a Starter Checklist, is what gets you off an emergency code and onto the right one.
Five mistakes people make with tax codes
A wrong tax code is silent — you only notice when you’ve over- or underpaid. These five errors, drawn from the recurring r/UKPersonalFinance and r/AskUK threads, are the ones that cost money.
Ignoring a W1, M1, or X on a new job
Starting a job often lands you on an emergency code that over-deducts tax, and many assume it’ll sort itself out without doing anything. It usually does — but only once HMRC has your details. Hand over your P45 or complete a Starter Checklist promptly to trigger the cumulative code and refund.
Cost: months of overpaid tax Fix: give your P45 or Starter ChecklistAssuming the employer can fix the code
Your employer can only use the code HMRC sends and can’t change it on request. People waste time asking payroll to adjust a wrong code. The correct route is HMRC, through your Personal Tax Account or by phone, who then issue an updated code to your employer.
Cost: a wrong code left in place Fix: contact HMRC, not your employerNot querying an old K code
A K code from a benefit you no longer have — a company car you handed back, for instance — keeps adding to your taxable pay until HMRC updates it. Codes lag reality, so if a benefit has ended, tell HMRC rather than waiting for the code to catch up on its own.
Cost: tax on a benefit you no longer get Fix: tell HMRC when a benefit endsOver-withholding on a low second job
A BR code on a small second job taxes it all at 20%, which can overpay if your main job doesn’t use your full allowance. Many never realise they could ask HMRC to split the allowance between employers, reducing the tax taken on the lower-paid job.
Cost: overpaid tax on the second job Fix: ask HMRC to split your allowanceNever checking the code at all
The most common error is simply not looking. A wrong code gives no warning — you quietly overpay for months or build up an underpayment that becomes a year-end bill. Glancing at your code on each payslip, especially after any change in your circumstances, is the simplest safeguard.
Cost: silent over- or underpayment Fix: check your code on every payslipFrequently asked questions
What does tax code 1257L mean?
1257L is the standard UK tax code. The number 1257 is your tax-free Personal Allowance of £12,570 divided by 10, and the letter L means you get the standard allowance with no special circumstances.
It’s the most common code in the country, used by around 85% of taxpayers with a single, straightforward job. If you have one job, no taxable benefits, and haven’t given away any Marriage Allowance, 1257L is what you’d normally expect to see.
What is an emergency tax code?
An emergency tax code is a temporary code applied when HMRC doesn’t have full information about your income — typically after starting a new job without handing over a P45. You’ll see a W1, M1, or X added to the end, for example 1257L M1.
The suffix means your tax is worked out non-cumulatively — each pay period in isolation, ignoring unused allowance from earlier in the year. This usually over-deducts tax, which is refunded automatically once HMRC issues a proper cumulative code.
How do I know if my tax code is wrong?
Check three things: whether there’s a W1, M1, or X on the end (emergency, likely overpaying), whether the number matches your allowance (usually 1257 for a simple job), and whether it reflects your current situation — a recent job change, new benefit, or second income can all leave it out of date.
Nothing alerts you to a wrong code, so it pays to glance at it on your payslip. If it looks off, contact HMRC — only they can change it. You can also view your code in your Personal Tax Account at gov.uk.
What does a K tax code mean?
A K code works in reverse. Instead of giving you tax-free pay, it adds an amount to your taxable income — the number times 10. So K475 adds £4,750. It’s used when your deductions exceed your Personal Allowance.
Common reasons are a company car or medical insurance, a State Pension alongside employment, or tax owed from a previous year. K codes are legitimate, but worth checking: if the benefit causing it has ended, the code should change, otherwise you’ll keep overpaying.
Why is my second job taxed at BR?
A BR code taxes all the income from that job at the basic rate of 20%, with no Personal Allowance, because your allowance is already used by your main job. For most people with a second job this is correct.
But if your total income is low and your main job doesn’t use all your allowance, you may be overpaying. You can ask HMRC to split your allowance between the two jobs. If you’re already a higher-rate taxpayer, the second job may be coded D0 (40%) instead.
How do I fix a wrong tax code?
For an emergency code, give your employer your P45 or complete a Starter Checklist — HMRC then issues a cumulative code and refunds any overpayment automatically. For anything else, contact HMRC through your Personal Tax Account or by phone.
Your employer can’t change the code themselves; they must use whatever HMRC sends. Overpaid tax within the current year is usually refunded through your payslips, while tax from earlier years is reclaimed separately. See gov.uk for the process.
What does an S or C in my tax code mean?
An S prefix means you pay Scottish income tax (for example S1257L), and a C prefix means Welsh income tax (C1257L). It’s based on where your main home is, not where you work or where your employer is based.
The Personal Allowance is the same £12,570, but the rates and bands differ — Scotland in particular has more bands than the rest of the UK. If you’ve moved between nations, check that the prefix matches your current main residence.
Will an emergency code refund itself?
Usually, yes — but only once HMRC has the information to move you onto a cumulative code. The overpaid tax from an emergency code is then refunded automatically through your payslips, often over the next few pay periods.
The key is making sure HMRC gets your details: hand your new employer your P45 or complete a Starter Checklist. If you’ve left a job and won’t have new employment for a while, you may be able to claim a refund directly from HMRC rather than waiting.
Related calculators
Your tax code drives what’s deducted from your pay, so it connects to your take-home, your allowances, and any second income. These calculators handle each piece.
Methodology & sources
How the checker reads a code
The checker breaks your tax code into its parts and explains each. The number is multiplied by 10 to give your tax-free Personal Allowance, so 1257 means £12,570. The letter signals your situation: L for the standard allowance, M and N for Marriage Allowance received or given, T for codes with other adjustments. Whole-word codes apply a single rate to all income from that source — BR at 20%, D0 at 40%, D1 at 45% — while 0T gives no allowance and NT deducts no tax. A K code is treated in reverse: the number times 10 is added to taxable pay rather than freed from tax. A leading S or C marks Scottish or Welsh rates, and a trailing W1, M1, or X marks an emergency, non-cumulative basis that taxes each pay period in isolation. The checker uses these rules to describe what your code does and to flag the situations, especially emergency suffixes and reduced numbers, that most often signal a code worth querying.
This is an explanatory tool, not a personal tax computation. Whether a code is correct depends on your full circumstances — your income, benefits, other jobs or pensions, allowances, and where you live — which only HMRC sees in full. The figures and conventions reflect the standard £12,570 Personal Allowance and current UK code rules. The aim is to help you understand and sanity-check your code, then point you to the right fix — not to replace advice from HMRC or an accountant.
Conventions used
- Number × 10 = tax-free Personal Allowance (1257 → £12,570)
- L standard · M / N Marriage Allowance received / given
- K reverse code: number × 10 added to taxable pay
- BR / D0 / D1 = all income at 20% / 40% / 45%
- 0T no allowance · NT no tax deducted
- S / C prefix = Scottish / Welsh rates
- W1 / M1 / X suffix = emergency, non-cumulative
- Only HMRC can change a code; employers must apply what’s issued