How to Change Your Tax Code with HMRC in 2026 [Guide]

You can change your tax code with HMRC by updating your employment or income details through your Personal Tax Account, via the HMRC app, or by contacting HMRC directly. 

HMRC updates your tax code whenever it receives new information about your income, benefits, pension, or employment situation. 

If your circumstances have changed and your tax code no longer reflects them, you should contact HMRC to update it. 

Here’s everything you need to know about changing your tax code.

Key points

• Tax code mistakes are more common than you might think 🔍
  Starting a new job, changing employers, receiving workplace benefits, claiming Marriage Allowance, or updating your pension income can all lead to tax code errors if HMRC's information is out of date.
• Check your tax code regularly 📋
  You can find your tax code on your payslip, tax coding notice, HMRC app, or Personal Tax Account. Reviewing it each year helps catch mistakes early and prevents financial problems down the line.
• Only HMRC can change your tax code ⚙️
  If your code is incorrect, you'll need to update your details through your HMRC Personal Tax Account, the HMRC app, or by contacting HMRC via phone or mail. Your employer can only apply the code HMRC provides.
• Keep your finances organised with ANNA 🚀
  Having accurate financial records makes it easier to spot tax code issues and keep HMRC's information up to date. ANNA helps you stay on top of income, expenses, and taxes so you’re never caught off guard.

What your tax code means

A tax code is a short combination of letters and numbers that tells your employer how much of your income to leave untaxed before deducting Income Tax. 

Most people on PAYE have the code 1257L.

The numbers represent your tax-free Personal Allowance divided by ten. So, 1257 corresponds to a £12,570 allowance, which is the amount you can earn each tax year before you start paying Income Tax. 

The letters tell HMRC and your employer about your tax situation, such as whether you're entitled to the standard Personal Allowance, paying tax on a second income, or being taxed under special rules. 

While 1257L is the most common code, you may see several others depending on your circumstances. 

Here's a quick reference for some other possible codes:

Why tax codes go wrong

HMRC builds your tax code using information it receives from employers, pension providers, and your own submissions. Because this isn't a live feed into your finances, errors creep in more often than people realise.

Common reasons for a wrong tax code include:

• Starting a new job
• Changing employers
• Receiving taxable workplace benefits, such as a company car or private medical insurance
• Claiming or losing the Marriage Allowance
• Receiving a change to your State Pension income
• Repaying tax that was underpaid in a previous tax year through your tax code

If your code ends in W1, M1 or X, you're on emergency tax. This usually happens when you start a new job, and HMRC doesn't yet have your income details. The code is meant to be a temporary measure, but it can result in you paying too much or too little tax until your records are updated. 

HMRC’s recent expense allowance removal

HMRC has reviewed many employment expense claims in recent years. In some cases, it removed flat-rate expense allowances where it believes the claim was no longer valid. 

When this happens, your tax code may change. For example, a change from 1307L to 1257L reduces your tax-free Personal Allowance by £500. This means more of your income becomes taxable.

For a basic rate taxpayer, the extra tax could be around £100 per year, while a higher rate taxpayer could pay around £200 more. If your tax code has changed unexpectedly, check your tax code notice or contact HMRC to understand what has been adjusted and whether the change is correct. 

How to check your current tax code

You can spot your tax code in a few places:

• Your most recent payslip (usually in the top section alongside your employee number)
• A tax coding notice (P2) sent by HMRC in the post, typically around March or April
• Your HMRC Personal Tax Account
• The HMRC app

HMRC advises checking your tax code as soon as it's issued. Catching errors early prevents months of overpaying or, worse, a surprise underpayment bill at the end of the tax year.

How to change your tax code

To change your tax code, you need to update the information HMRC uses to calculate it. HMRC will then review the details and issue a new code if a correction is needed. 

While your employer applies the code to your pay, only HMRC can create or amend it. 

The fastest way to report changes is through your HMRC Personal Tax Account. 

Here’s how:

• Sign in to your Personal Tax Account: Go to gov.uk and sign in. You'll need two forms of ID to verify your identity. Most people use a passport or driving licence alongside a recent P60 or payslip.
• Go to the PAYE section: Navigate to PAYE: Income Tax and select Check your Income Tax.
• Review the information HMRC has about you: Look at the information HMRC is using, including your salary, pension details, and any benefits in kind, such as a company car. If anything is missing, out of date, or wrong, update it directly in the account.
• Submit your changes: Once you've corrected the information, submit the update. HMRC will review it and issue a new code to your employer.
• Check your next payslip: After you report a change, HMRC will contact you and your employer or pension provider to confirm the updated code. Your next payslip should show the revised code along with any adjustments to your pay.

💡 Did you know? 

ANNA's business account keeps your income and expenses organised in one place, so you can easily spot discrepancies between what HMRC holds on file and your actual earnings. This is particularly useful if you're self employed or have income from multiple sources.

If you can't fix it online

You may need to contact HMRC directly if your tax code issue involves multiple employments, benefits-in-kind, pension income, or other circumstances that require additional information or manual review. 

You can call HMRC directly on 0300 200 3300. 

Before you call, prepare your National Insurance number, current tax code, employer details, and a clear explanation of what you believe is wrong.

You can also write to HMRC. This method is significantly slower, so you should plan ahead and allow several weeks for a response.

What happens after you report a change

Once HMRC updates your code, the correction is automatically applied to your payroll. If you've overpaid tax because of an incorrect code, you'll usually receive the difference back through your pay rather than as a separate refund. 

If the change happens mid-year and you've paid less tax than you should have, you may see a larger deduction in a future pay as payroll software recalculates your tax position.

🧠 Good to know: 

If you're also completing a Self Assessment return, for example, because you're a sole trader or a landlord, any remaining overpayment or underpayment for the tax year will be settled through that process.

Stay on top of your tax code with ANNA

Tax code problems often happen because HMRC is working with incomplete or outdated information. Keeping accurate records of your income, expenses, benefits, and business finances can make it easier to spot mistakes and understand why your tax code has changed.

ANNA helps you stay organised year-round, giving you a clearer view of your finances and making tax admin nearly effortless.

Here’s how:

• Automatic expense categorisation: Transactions are automatically sorted into the right categories, reducing manual bookkeeping and helping keep your records accurate.
• Real-time tax estimates: Get an up-to-date view of your potential tax liabilities as income and expenses are recorded, and avoid surprises when tax deadlines arrive.
• Business account and bookkeeping in one place: Manage your banking, transactions, and bookkeeping from a single platform to instantly see your overall financial position.
• Smart Auto Accountant: Keep your books up to date, monitor live tax estimates, prepare tax filings, and get instant answers to business finance questions from an AI accountant that works around the clock. 
• Receipt capture and storage: Snap a photo of a receipt and store it digitally alongside your transactions to create an organised audit trail without piles of paperwork.
• Free Self Assessment filing: File your Self Assessment return at no extra cost with ANNA. If you've already paid another provider's filing fee, ANNA will cover the cost when you switch.
• Tax deadline reminders: Receive timely alerts for key filing and payment deadlines to stay compliant and avoid penalties.
• Professional invoicing tools: Create, send, and track invoices from one place so you can get paid faster and maintain a clear record of business income.
• Dedicated tax pots: Set money aside automatically for future tax bills, simplify budgeting, and prepare for payments as they come.
• 24/7 customer support: Access support whenever you need it, whether you have a question about your account, bookkeeping, or tax-related admin.

Don't wait for a tax code mistake to become a tax bill. Join ANNA today and stay on top of your finances year-round.