Ever looked at your payslip and thought, “That’s not what I expected”?
Often, the culprit is your tax code.
Tax codes decide how much tax comes out of your pay. If they’re wrong, you could end up paying too much or too little.
The good news is that fixing it is not complicated anymore. HMRC has made the process easier, and you can now sort it out online without waiting on hold for hours.
This article will walk you through:
- Why your tax code matters,
- Where you can find your tax code,
- How to change tax code online, and
- Much More…
Let’s get into it!
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What Is a Tax Code?
A tax code is a short combination of numbers and letters used by HMRC. It tells your employer or pension provider how much tax-free income you’re entitled to before tax is deducted.
For example: 1257L means you get the standard personal allowance of £12,570.
Why Tax Codes Are Important?
Tax codes are important because they decide how much tax you pay each month.
If your code is too low: You might be taxed on income that should be tax-free. This means less money in your pocket today and a likely refund later, which isn’t ideal for budgeting.
If your code is too high: This is more dangerous. It means you are not paying enough tax now. While your take-home pay might look good initially, you’ll likely face an unexpected tax bill from HMRC at the end of the tax year.
Types of Tax Codes
Here’s a quick table showing the most common tax codes and what they mean:
| Tax Code | Meaning | Who It Applies To |
| 1257L | Standard personal allowance | Most employees in 2025/26 |
| BR | Basic rate only | Second jobs or pensions |
| D0 | Higher rate only | High-income jobs (40%) |
| D1 | Additional rate only | Very high-income jobs (45%) |
| K | Income exceeds personal allowance | Some benefits or unpaid tax adjustments |
| NT | No tax taken | Tax-exempt income |
| 0T | No personal allowance | Emergency or unknown situation |
How Do I Check My Tax Code?
You can check your tax code in several places:
- On your payslip: Your tax code is usually printed on your monthly or weekly payslip.
- On your P60: Your employer provides a P60 form at the end of each tax year, which includes your tax code.
- Online: Sign in to your Personal Tax Account on the GOV.UK website to see your current tax code. This is the fastest method to check your tax code. You can check it immediately after logging in.
- HMRC App: Your tax code is also available via the HMRC app.
- Coding notice: HMRC sends a P2 notice of coding each year, usually in January or February, to explain your tax code.
How To Change Tax Code Online?
Okay, first things first. You don’t directly change the code yourself. Instead, you change the information that HMRC uses to calculate your code. HMRC then automatically generates the new code and sends it to your employer.
The easiest way to do this is via your Personal Tax Account online.
- Sign in: Go to the GOV.UK website and sign in using your Government Gateway ID and password.
If you haven’t used it before, you can create an account. This usually requires your National Insurance number and something to verify your identity (for example, a payslip or passport).
- Report a change: Look for the “Pay As You Earn (PAYE)” section and select “check current tax year”.
- Update your details: Click on “view or update employment details” to report any changes, such as a different job, income level, pension, or taxable benefits.
- Confirm and submit: Once you have entered the correct information, HMRC will be notified and may issue an updated tax code.
- Notify your employer: HMRC will send the revised tax code directly to your employer or pension provider. The new code will then be reflected on your next payslip.
What Happens After You Report a Change?
Once you report a change online, HMRC will review the new information.
- If your tax code needs to change, they will send you a new tax code notice (P2).
- Crucially, they will also notify your employer or pension provider directly using a P6 notice.
- Your new tax code should then appear on your next payslip, along with any adjustment to the tax you’ve already paid (a refund or extra deduction).
What If I Don’t Have an HMRC Online Account?
While setting up a Personal Tax Account is highly recommended as it’s the fastest and most efficient method, you still have traditional options:
- Call HMRC: You can contact the HMRC Income Tax helpline by calling 0300 200 3300. Ensure you have your National Insurance number, recent payslips, and details of the changes you need to report ready before you call.
- Webchat: HMRC offers a webchat service which can sometimes be quicker than waiting on the phone lines. You can usually access this via the help pages on the GOV.UK website.
- Write to HMRC: You can write to HMRC to change your tax code, but it is generally faster to use the online service or phone the helpline. Writing to HMRC can result in long delays in response.
Why Would I Want To Change My Tax Code?
A change in your life or financial situation is the usual reason your code shifts. It’s definitely worth checking if any of these common scenarios apply to you:
- You think you’re paying too much tax and want HMRC to correct it.
- You’re worried you’re paying too little tax and want to avoid a later bill.
- You’ve started a new job and the system has put you on the wrong or temporary code.
- You have more than one job or a mix of job and pension income, and your allowance is going to the wrong place.
- You’ve started receiving taxable benefits like a company car or medical insurance.
- You’ve stopped receiving a benefit and don’t want to keep paying extra tax for it.
- Your income estimate for the year is higher or lower than what HMRC is using.
- You’ve claimed or cancelled Marriage Allowance.
- You notice wrong information on your tax code, such as old jobs or incorrect benefits.
- You’ve been placed on an emergency tax code and need HMRC to update your details.
What Are Emergency Tax Codes?
Emergency tax codes are temporary measures HMRC uses when it doesn’t have enough information to give you the correct tax code. This often happens when you:
- Start a new job and haven’t provided a P45 from your previous employer.
- Start a second job.
- Begin receiving a state pension.
These codes are usually a standard number followed by W1 (Week 1), M1 (Month 1), or X. They generally work on a non-cumulative basis, meaning they only tax your pay for that specific pay period without considering your year-to-date earnings or full Personal Allowance.
The result? You often end up paying too much tax temporarily. Once HMRC gets all your details sorted out, they will send a proper tax code, and you will get a refund for any overpaid tax.
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What If My Tax Code Is Wrong?
It’s crucial to correct a wrong tax code as soon as you spot it. If it’s wrong, you’re either paying too much tax (meaning you’re losing out on take-home pay each month) or too little (meaning you’ll have to pay it back later).
Here’s what to do:
- Check your details: First, log in to your Personal Tax Account on the GOV.UK website. Make sure all the information HMRC holds on you is correct your salary, benefits, and any other income.
- Report the error: If you find incorrect information, report it through the online service. This usually involves clicking “Update your details” in the “Check your Income Tax” section.
- HMRC fixes it: HMRC will investigate and issue a new, correct tax code to you and your employer.
- Get a refund or pay up:
- Overpaid tax: If you’ve paid too much, HMRC will refund you automatically. It might come through your payslip, or you’ll get a P800 form at the end of the tax year.
- Underpaid tax: If you haven’t paid enough, HMRC will collect the debt. For small amounts, they often adjust your next year’s tax code to spread the cost. For larger sums, they will contact you to set up a payment plan.
Are you looking for professional tech-savvy tax advisors and accountants in the UK to guide you? Contact us now!
The Bottom Line
Tax codes may look complicated, but they’re simply HMRC’s way of making sure you pay the right amount of tax. It is your responsibility to make sure HMRC has the correct, up-to-date information so that the tax you pay is right.
Most mistakes are fixable, and thanks to the Personal Tax Account, correcting your tax code online is now the quickest and most straightforward way to get your finances in order for the 2025/2026 tax year.
Get into the habit of checking it every tax year, especially after any major life change.
WE CAN HELP
If you’re feeling unsure about changing your tax code, or you want someone to guide you through the process, we’re here for you. At Accotax, our chartered accountants know how to work with HMRC, help you check and correct your tax code.
We offer a range of packages designed to fit your unique needs!
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Disclaimer: All the information provided in this article on how to change tax code online, including all the texts and graphics, is general in nature. It does not intend to disregard any of the professional advice.