Is My HMRC Tax Code Wrong?

Who this guide is for

Anyone in the UK who pays tax through PAYE on wages from a job or on a pension, and wants to know what their tax code means, whether it looks wrong, how to get it corrected and how to get back tax they have overpaid. It also covers who needs to send a Self Assessment tax return, its deadlines and penalties, Making Tax Digital for Income Tax, paying a tax bill in instalments, and appealing an HMRC decision or penalty. Tax codes work the same way in England, Wales, Scotland and Northern Ireland. If you live in Scotland you pay Scottish Income Tax rates and your tax code starts with S: see the Scotland section below.

What this guide does not cover

• National Insurance, and how tax on savings interest, dividends or property income is worked out. This guide does not cover them: check GOV.UK or ask HMRC.
• Whether the off-payroll working rules (IR35) apply to your contract: use the IR35 checker.
• Tax on foster care income: use the foster carer tax checker.

The questions that decide the answer

1. What is your full tax code, including any letters before or after the numbers, such as S, C, K, BR, 0T, W1, M1 or X? It is on your payslip.
2. Where do you live: England, Wales, Scotland or Northern Ireland? Have you moved between them during this tax year?
3. How many jobs or pensions do you have, and which one is this code for?
4. Have you started or left a job, started a pension, the State Pension or taxable benefits, or started getting a company benefit such as a car or medical insurance? When?
5. Did you give your new employer a P45 from your last job?
6. Which tax year is the problem in? A tax year runs from 6 April to 5 April the following year.

"What do the numbers in my tax code mean?"

The numbers tell your employer or pension provider how much tax-free income you get from them in that tax year.

To work out the number, HMRC starts with your tax-free Personal Allowance. It takes off any income you have not paid tax on, such as untaxed interest or part-time earnings, and any other deductions in your code, such as company benefits or the High Income Child Benefit Charge. It then replaces the final digit with a letter.

The standard Personal Allowance for the 2026 to 2027 tax year (6 April 2026 to 5 April 2027) is £12,570. That is where the code 1257L comes from.

If you have a K in your tax code, the calculation is different: see the K code section below.

When your tax code changes, HMRC will usually write to explain how it worked out your new code. You can also see how it was worked out in the Check your Income Tax online service.

"What do the letters in my tax code mean?"

• L: you get the standard tax-free Personal Allowance.
• M: Marriage Allowance. You have received a transfer of 10% of your partner's Personal Allowance.
• N: Marriage Allowance. You have transferred 10% of your Personal Allowance to your partner.
• T: your tax code includes other calculations to work out your Personal Allowance.
• 0T: your Personal Allowance has been used up, or you have started a new job and your employer does not have the details it needs to give you a tax code.
• BR: all your income from this job or pension is taxed at the basic rate. It is usually used if you have more than one job or pension.
• D0: all your income from this job or pension is taxed at the higher rate. D1: all of it is taxed at the additional rate. Both are usually used if you have more than one job or pension.
• NT: you are not paying any tax on this income.
• K: you have income you are not paying tax on that is more than your Personal Allowance: see the K code section below.
• S at the start: your income or pension is taxed at Scottish rates, for example S0T or SBR.
• C at the start: your income or pension is taxed at Welsh rates, for example C0T, CBR, CD0 or CD1.
• W1, M1 or X at the end, or NONCUM: you are on an emergency tax code: see the next section.

"Am I on an emergency tax code?"

You are on an emergency tax code if your tax code ends in W1 (used when you are paid weekly, for example 1257L W1), M1 (used when you are paid monthly) or X (used when your pay dates vary). Your payslip may show NONCUM instead, depending on your employer's payroll software. If your code does not end in W1, M1, X or NONCUM, you are not on an emergency tax code.

Normally your tax is worked out on your total income so far in the tax year. On an emergency tax code, it is worked out on what you are paid in that week or month only, as if you were paid that amount every week or month of the year. This can mean you pay the wrong amount of tax.

If you have started a new job: if your new employer does not have your previous income and tax details, it pays you on an emergency tax code. This is usually temporary. Give your new employer the P45 from your previous job. If your previous employer did not give you a P45, ask it for one.

HMRC usually updates your tax code once it has your details from your new and previous employers, and sends the new code to you and your new employer. This can take up to 35 days from when you start the job. If you have paid too much tax, you can get a refund. If you have not paid enough, you stay on the emergency tax code until you have paid the correct tax for the year.

If you started the job more than 35 days ago and still think your tax code is wrong, check and update your details (see below).

If you have started getting company benefits or the State Pension: you might be put on an emergency tax code. This is normal and helps you pay the right amount of tax for that tax year. Check online that your tax code includes the company benefit or the State Pension. If it does not, update your details or contact HMRC. You keep the emergency tax code until the end of that tax year, and get a non-emergency code in the new tax year.

"What does a K in my tax code mean?"

A K code means you have income or deductions that are higher than your tax-free Personal Allowance and are not already being taxed. This can happen when you:

• are paying tax you owe from a previous year through your wages or pension;
• get the State Pension or taxable state benefits;
• get company benefits you pay tax on, such as a company car; or
• get more interest on your savings than your Personal Savings Allowance.

Your employer or pension provider uses the K code so that you pay the tax on your other income or deductions through that job or pension.

Employers and pension providers cannot take more than half of your pre-tax wages or pension when using a K tax code.

"How do I check and correct my tax code?"

Your tax code is on your payslip. Using HMRC's Check your Income Tax online service is the quickest way to check and update the details HMRC holds:

1. Sign in to the Check your Income Tax online service on GOV.UK.
2. Check your employment, pension, estimated taxable income, company benefit and expenses details.
3. Update anything that is wrong or missing.
4. Claim tax relief on your employment expenses, if you have any.

If you have left a job and did not get a P45, ask your former employer for one. This can help HMRC update your details.

If you cannot use the online service, contact HMRC: call the Income Tax helpline on 0300 200 3300. If you have just started a new job, wait 35 days for HMRC to get your new income details before you contact it.

If your tax code needs to change, HMRC will update it. HMRC will tell you and your employer the new tax code within 15 working days.

After you get your new tax code, it should appear on your next or the following payslip if you are paid monthly, or on your third payslip if you are paid weekly. If your payslip does not show the new code, ask your employer to check it has received it.

If you want to help a friend or family member with their tax, you can register as their trusted helper on GOV.UK.

"I think I have paid too much or too little tax"

If you are on the wrong tax code, you may pay too much or too little tax. You can get a refund, or pay what you owe, once HMRC has your income details for the tax year.

If you paid too much: when HMRC updates your tax code and has all your income details for the tax year, it works out the difference and asks your employer or pension provider to refund it through your pay. This usually happens when they start using your new tax code. If HMRC does not have your details, you cannot get a refund until it gets them from your employer, pension provider or the benefits office.

If you paid too little: HMRC estimates how much you owe when it updates your tax code, and adjusts your tax code to collect it over one or more tax years where it can.

After the tax year ends: HMRC gets income details from employers, pension providers and the benefits office and checks how much tax you paid. If you are employed or get a pension and you did not pay the right amount, it sends you either a tax calculation letter (P800) or a Simple Assessment letter. The letter tells you how to get your refund or pay what you owe. These letters are sent between June and March after the tax year ends. If you are registered for Self Assessment, you do not get one of these letters: your Self Assessment bill is adjusted instead.

If you think you have paid too much tax and HMRC has not sent you a letter, you can claim a refund through GOV.UK. If you think you owe tax and have not had a letter, contact HMRC.

You can claim back overpaid Income Tax up to 4 years after the end of the tax year you overpaid it in. In the 2026 to 2027 tax year, the earliest year you can still claim for is 2022 to 2023, and that claim must be made by 5 April 2027.

"I live in Scotland"

You pay Scottish Income Tax if you live in Scotland. It is paid to the Scottish Government. It applies to your wages, your pension and most other taxable income. You pay the same tax as the rest of the UK on dividends and savings interest.

If you pay Scottish Income Tax, your tax code starts with S. That is not a mistake.

Scottish Income Tax rates for the 2026 to 2027 tax year, if you have the standard Personal Allowance of £12,570:

• Personal Allowance: up to £12,570 at 0%
• Starter rate: £12,571 to £16,537 at 19%
• Basic rate: £16,538 to £29,526 at 20%
• Intermediate rate: £29,527 to £43,662 at 21%
• Higher rate: £43,663 to £75,000 at 42%
• Advanced rate: £75,001 to £125,140 at 45%
• Top rate: over £125,140 at 48%

Scottish codes for a job or pension where all the income is taxed at one rate: SBR (basic rate), SD0 (intermediate rate), SD1 (higher rate), SD2 (advanced rate) and SD3 (top rate). They are usually used if you have more than one job or pension.

You pay Scottish Income Tax if you move to Scotland and live there for longer than anywhere else in the UK during a tax year. You must tell HMRC your new address if you move to or from Scotland. If you do not, you may pay tax at the wrong rate.

If HMRC changes your tax rate because you moved, the new rate is backdated to the start of the tax year (6 April) in which you moved. The tax taken from your wages or pension is adjusted automatically so you pay the right amount across the whole year.

"I live in England, Wales or Northern Ireland"

Income Tax rates for the 2026 to 2027 tax year in England, Wales and Northern Ireland, if you have the standard Personal Allowance of £12,570:

• Personal Allowance: up to £12,570 at 0%
• Basic rate: £12,571 to £50,270 at 20%
• Higher rate: £50,271 to £125,140 at 40%
• Additional rate: over £125,140 at 45%

If you live in Wales, you pay the Welsh rates of Income Tax, set by the Welsh Government, and your tax code starts with C. For the 2026 to 2027 tax year the Welsh rates and bands are the same as in England and Northern Ireland. You pay the same tax as the rest of the UK on dividends and savings interest.

You pay the Welsh rates if you live in Wales for longer than anywhere else in the UK during a tax year. If you move to or from Wales, update your address with HMRC. The new rates are backdated to the start of the tax year in which you moved, and the tax taken from your wages or pension is adjusted automatically.

"I earn over £100,000"

Your Personal Allowance goes down by half of the amount by which your adjusted net income is above £100,000. It is zero if your income is £125,140 or above. This applies anywhere in the UK.

"Do I need to send a Self Assessment tax return?"

• You must send one if, for example, you were self-employed as a sole trader and earned more than £1,000 (before taking off expenses), you were a partner in a business partnership, you had to pay Capital Gains Tax, or you had to pay the High Income Child Benefit Charge and do not pay it through PAYE.
• Renting out property: the first £1,000 of rental income is tax-free. Over £2,500 after expenses (or over £10,000 before expenses) you must send a return. If it is between £1,000 and £2,500: contact HMRC.
• Other untaxed income may also mean you need one: use GOV.UK's "Check if you need to send a Self Assessment tax return".
• Earning a high income taxed only through PAYE is no longer a reason on its own (that rule ended from the 2024 to 2025 tax year).
• Tell HMRC by 5 October after the end of the tax year if you need to send a return and have not sent one before, or did not need to send one for the year before.

"Self Assessment deadlines and penalties"

• For the 2025 to 2026 tax year: paper return by 31 October 2026, online return by 31 January 2027, and pay by 31 January 2027 (by 11:59pm).
• Payments on account are two advance payments towards next year's bill, each half of last year's tax, due 31 January and 31 July. You do not have to make them if last year's bill was under £1,000 or if more than 80% of your tax was taken at source (for example through PAYE).
• You can correct a return within 12 months of the 31 January deadline.
• Late return: £100. After 3 months, £10 a day up to £900. After 6 months, 5% of the tax due or £300 (whichever is more). After 12 months, the same again.
• Late payment: 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest.
• Making Tax Digital: if you had to start using it on 6 April 2026, these penalties still apply to your 2025 to 2026 return due 31 January 2027. The new penalties start from the tax year you join. If you volunteered for Making Tax Digital, the new penalties replace these on your tax return.

"Do I have to use Making Tax Digital?"

• Sole traders and landlords registered for Self Assessment must use Making Tax Digital for Income Tax if their qualifying income was over £50,000 in 2024 to 2025 (from 6 April 2026), over £30,000 in 2025 to 2026 (from 6 April 2027), or over £20,000 in 2026 to 2027 (from 6 April 2028).
• Qualifying income is your self-employment and property income before expenses. Wages, pensions and partnership income do not count. Partnerships will join later (no date yet), and some people are exempt.
• You keep digital records and send an update every 3 months using software that works with Making Tax Digital. Updates are summaries, not tax returns. They are due 7 August, 7 November, 7 February and 7 May. You still send a tax return through the software.
• There are no penalties for a missed quarterly update in the 2026 to 2027 tax year.

"I can't pay my tax bill on time"

• You may be able to set up a payment plan to pay in weekly or monthly instalments by Direct Debit. HMRC checks that the plan is affordable.
• You can set one up online if you owe £30,000 or less, are up to date with your tax returns, and have no other tax debts or HMRC payment plans. Otherwise call HMRC on 0300 123 1813 (from outside the UK +44 2890 538 192).
• Interest is charged on a payment plan (Bank of England base rate plus 4%).

"Appealing an HMRC decision or penalty"

• A penalty: appeal usually within 30 days of the date the penalty was issued, online or by post (form SA370). You do not have to pay the penalty until the appeal is settled.
• A reasonable excuse means something stopped you meeting the deadline for a valid reason, and you then sent the return or paid as soon as you could. GOV.UK says these do not count: not having enough money, finding the online system too difficult, not getting a reminder from HMRC, and mistakes on your return.
• Other decisions (for example a tax bill or a change to your return): you usually have 30 days from the date of the decision letter to appeal to HMRC, saying what you disagree with and why. HMRC may offer a review, you can ask for one, or you can go straight to the First-tier Tribunal (Tax).
• If HMRC offers a review of an Income Tax, Capital Gains Tax or National Insurance decision, you have 30 days from the offer to accept it or appeal to the tax tribunal. Reviews usually take 45 days. After a review, appeal to the tax tribunal usually within 30 days of the review result letter (online or form T240). If you are late, you must explain why: HMRC or the tax tribunal can still allow it.
• Paying while you appeal: for Income Tax and other direct taxes you can ask to delay paying the tax in dispute. For VAT and other indirect taxes you usually have to pay first, unless that would cause hardship.
• Complaints about HMRC's service (delays, mistakes, how you were treated) are different from appeals: complain to HMRC, then to the Adjudicator's Office (free and independent, normally within 6 months of HMRC's second review), then through your MP to the Parliamentary and Health Service Ombudsman.

Deadlines and timings

• After a change is needed, HMRC tells you and your employer the new tax code within 15 working days.
• After you start a new job, HMRC can take up to 35 days to update your tax code. Wait 35 days before contacting HMRC about it.
• Tax calculation letters (P800) and Simple Assessment letters are sent between June and March after the tax year ends.
• Refund claims for overpaid Income Tax: up to 4 years after the end of the tax year. For 2022 to 2023, claim by 5 April 2027.
• Self Assessment, 2025 to 2026 tax year: paper return by 31 October 2026; online return and payment by 31 January 2027. Tell HMRC you need a return by 5 October after the tax year ends.
• Appealing an HMRC decision or penalty: usually within 30 days.

Traps

• A code starting with S (Scotland) or C (Wales) is not a mistake if you live there.
• BR, D0 or 0T on a second job or pension is not always wrong: these codes are usually used when you have more than one job or pension.
• An emergency code (W1, M1, X or NONCUM) is usually temporary after a new job. Giving your new employer your P45 helps.
• A new tax code does not show at once: it can take until the next or following payslip if you are paid monthly, or the third payslip if you are paid weekly.
• If you move to or from Scotland or Wales, the rates for the whole tax year depend on where you lived longest that year. Tell HMRC your new address.
• Under a K code, no more than half of your pre-tax wages or pension can be taken.
• Overpaid tax from more than 4 years after the end of the tax year cannot be claimed back.