How to Change My Tax Code in 2026?

Quick answer: To change your tax code, contact HMRC directly. The fastest way is online through your Personal Tax Account or the HMRC app, where you can update your income details. HMRC then issues a corrected code and tells your employer, usually within 15 working days. You cannot change your own tax code, and neither can your employer - only HMRC can.

Here's a fact that catches most people out: HMRC now updates tax codes mid-year using information sent by third parties, like your bank reporting your savings interest. That means your code can change without you doing a single thing, and the first you'll know about it is a smaller pay packet. One Reddit user spent months puzzling over a surprise emergency code, only to discover HMRC had quietly adjusted it because of £1,800 in untaxed interest from accounts he'd half-forgotten about.

If your code is wrong, you're either overpaying tax (your money sitting with HMRC) or underpaying it (a nasty bill heading your way later). Neither is great. The good news? Sorting it is usually quicker and simpler than people fear. But before delving into any deeper, see if HMRC automatically refunds overpaid tax.

This guide walks you through exactly how to change your tax code, where to do it, how long it takes, and what to do for those specific codes that keep tripping people up - 0T, BR, emergency codes, 1131N and more.

Key Takeaways

• Only HMRC can change your tax code - not you, and not your employer. Your job is to give HMRC the right information.
• The quickest route is online via your Personal Tax Account or the HMRC app.
• Changes usually take up to 15 working days for HMRC to update and notify your employer.
• Most wrong codes come from missing or outdated information - a second job, savings interest, benefits in kind, or unused personal allowance.
• You won't lose out long-term. If you've overpaid, HMRC refunds you. If you've underpaid, it's usually collected through your code over time.

What Is a Tax Code, and Why Does It Matter?

A tax code is the mix of numbers and letters your employer or pension provider uses to work out how much Income Tax to take from your pay under the PAYE (Pay As You Earn) system.

The numbers show your tax-free Personal Allowance. The letters describe your situation. The most common code for 2025/26 and 2026/27 is 1257L, which means you can earn £12,570 a year before paying any tax.

Here's a quick reference for the codes people ask about most:

Get the code right and your take-home pay is correct throughout the year. Get it wrong and you're either short-changed each payday or building up a bill without realising.

Where Do I Change My Tax Code?

You change your tax code by telling HMRC the correct information about your income - and the best place to do that is online. Remember, you can't simply pick a new code yourself. You give HMRC the facts, and HMRC issues the corrected code.

You've got four main options:

• Online - Personal Tax Account (fastest). Sign in at GOV.UK to "Check your Income Tax for the current year." You can update your estimated income, add or remove a job, and report things like company benefits ending. HMRC recalculates and reissues your code.
• The HMRC app. You can check your tax code and update details straight from your phone. Download it from GOV.UK and log in with your Government Gateway details.
• By phone. Call the Income Tax helpline on 0300 200 3300. Useful for anything the online service won't let you fix, like swapping codes between two jobs.
• Through the PAYE system automatically. When you start a new job, your P45 or starter checklist gives your employer enough to apply the right code. Once HMRC processes it, they'll issue an updated code if needed.

For most people, the Personal Tax Account does the job in a few minutes. As one HMRC adviser put it on a community forum: just "pop onto the gov website, update the estimated income, and they'll swap the codes for you."

How Do I Contact HMRC About a Tax Code?

If the online service can't sort it, you'll need to speak to HMRC directly. Here are your options:

• Phone: Call the Income Tax helpline on 0300 200 3300. Lines are open Monday to Friday, 8am to 6pm. Be warned - waits of 13 minutes or more are common, so call early if you can.
• Online:Use your Personal Tax Account at GOV.UK. Many code issues can be fixed here without ever picking up the phone.
• HMRC app: Check your code and message HMRC without queuing on the phone.

Before you get in touch, have your National Insurance number and a recent payslip or P60 handy. If you're querying why a code changed, log into your Personal Tax Account first - your tax coding notice explains exactly how HMRC worked it out, which often answers the question before you even call.

How Long Does It Take for HMRC to Change Your Tax Code?

Once HMRC has the correct information to update an employee's tax code, they aim to notify you and the employee within 15 working days.

When you receive the new tax code, you must apply it on the employee's next available payday. The change should be reflected in their next pay cycle, though this can vary depending on when you receive the notice.

A few things worth knowing:

• If an employee has overpaid tax, the corrected code often adjusts their subsequent pay automatically, and you'll refund them the extra through their wages.
• If an employee has been underpaid, HMRC typically "codes in" the shortfall, allowing you to spread the repayment across future pay packets rather than them receiving a single bill.
• Changes made late in the tax year (close to 5 April) might not be fully processed in time. When this happens, HMRC will reconcile the employee's tax after the year-end and issue a P800 calculation to settle any over- or underpayments.

How Do I Get My Tax Code Swapped Between Two Jobs?

It's a common issue for employees with multiple jobs: HMRC applies their Personal Allowance (1257L) to a lower-paid role, leaving a BR code on their main income. This results in them being overtaxed each month, which can cause confusion and frustration.

Here's what this means for you as an employer and how your employee can resolve it:

• If your new employee's second job earns under £12,570 a year: The employee should log into their Personal Tax Account and update their estimated income for each job. HMRC's system should then automatically reallocate their Personal Allowance and swap the tax codes.
• If both jobs earn over £12,570: It doesn't matter which job holds the Personal Allowance; their total tax for the year will be correct.
• If one job has irregular hours: It's best for the employee to call HMRC on 0300 200 3300 and ask an agent to swap the codes manually.

It's important to note that HMRC sometimes needs a few payslips to establish a clear earnings pattern before they can process the change. If the employee has updated their details online but their tax code remains incorrect after a couple of pay cycles, advise them to call HMRC directly.

What about splitting the allowance?

If an employee has two low-paid jobs that, combined, earn less than the £12,570 Personal Allowance, they can ask HMRC to split their allowance between both roles. This prevents either employer from deducting tax. You cannot arrange this for them; the employee must contact HMRC to make this request.

Why Is My Tax Code Incorrect?

Most wrong tax codes come down to one thing: HMRC doesn't have accurate, up-to-date information about your income. When that happens, they make an estimate - and estimates can be off.

Here are the usual culprits:

• You started a new job without handing over a P45 or completing a starter checklist (hello, 0T or emergency code).
• You have a second job or pension and your Personal Allowance has been applied to the "wrong" one.
• Savings interest. Banks report your interest to HMRC, and if it exceeds your Personal Savings Allowance (£1,000 for basic-rate taxpayers, £500 for higher-rate taxpayers), HMRC adjusts your tax code to collect the tax.
• Benefits in kind, like private medical insurance or a company car - people genuinely forget these affect their code.
• Underpaid tax from a previous year is being collected through your current code.
• Work expenses or tax relief changing, sometimes after a refund claim.
• Marriage Allowance kicking in or ending (that's where 1131N and 1383M come from).

The lesson from real taxpayers? Don't assume your code is wrong just because it changed. As one finance forum regular wisely noted, "an emergency tax code isn't necessarily an incorrect tax code." Always check your coding notice first to see what HMRC has actually assumed.

How Do I Update My Details Online if My Tax Code Is Wrong?

If your code is wrong, the online route is genuinely the easiest fix. Here's the step-by-step:

• Sign in to your Personal Tax Account at GOV.UK (search "Check your Income Tax for the current year"). You'll need a Government Gateway ID - if you haven't logged in for a while, you may need to re-register.
• Check your tax code and coding notice. This breaks down exactly how HMRC calculated your code, including any estimated interest, benefits, or allowances.
• Spot what's wrong. Maybe your estimated income is too high, a job you've left is still listed, or a benefit you no longer get is included.
• Update the details. You can change your estimated pay, remove old employments, or correct company benefits directly in the service.
• Submit and wait. HMRC recalculates and issues a new code, typically within 15 working days, notifying your employer too.

If the thing that's wrong can't be edited online - like a stubborn emergency code or a two-job swap that won't update - that's your cue to call 0300 200 3300.

How Do I Change an Emergency Tax Code?

These specific codes have their own quirks, so here's how to tackle each one.

Emergency codes (1257L W1, 1257L M1, 1257L X): These appear when HMRC doesn't have your full details yet - often after starting a new job without a P45. The fix is usually to complete your employer's starter checklist and make sure HMRC has your previous employment details. Once they do, they'll move you onto a normal cumulative code and refund any overpaid tax.

How to Change 0T Tax Code?

0T tax code: This means no Personal Allowance is being applied, so you're taxed on everything. It often happens when a new starter doesn't provide a P45 or starter checklist. Speak to your employer first to check whether they need your P45 or P60. If they have everything and the code still doesn't update, contact HMRC.

How to Change BR Tax Code?

BR tax code: BR taxes all income at 20% with no allowance - perfectly correct for a second job, but wrong if it's your only income. If BR is on your sole job, contact HMRC to get it changed to 1257L (or your correct code).

Tax code 1257l M1: How to Change?

1257L M1 / non-cumulative codes: The M1, W1 or X means your tax is calculated on each pay period in isolation, ignoring what you've earned earlier in the year. To switch to a cumulative basis, HMRC needs your full year-to-date pay and tax details - usually from your P45 or a starter checklist. Once they have it, they'll reissue a cumulative code.

How to Change Tax Code for Marriage Allowance

1131N (Marriage Allowance): This isn't an error - it means you've transferred 10% of your Personal Allowance to your spouse or civil partner. If your circumstances change (a break-up, or your income rising so the transfer no longer makes sense), you can cancel or change Marriage Allowance through your Personal Tax Account or by contacting HMRC.

How Do Employers Change a Tax Code on Basic PAYE Tools?

A quick note for employers using HMRC's free Basic PAYE Tools software: you must only change an employee's tax code when HMRC tells you to, via a P6 or P9 coding notice. Never change it off your own back.

To update it: select the employee, choose the "tax code change" option from the menu, enter the new code from HMRC's notice, and apply it from the correct effective date. It's a straightforward process, but the golden rule stands - wait for HMRC's instruction first.

TL;DR - The Short Version

• You can't change your own tax code - only HMRC can. You provide the correct information; they issue the code.
• Fastest method: update your details online via your Personal Tax Account or the HMRC app.
• Can't fix it online? Call HMRC on 0300 200 3300 (8am–6pm, Mon–Fri).
• Timeframe: HMRC updates your code and tells your employer within 15 working days.
• Two jobs? Update your estimated income online to swap codes; call HMRC if one job is irregular.
• Wrong code? Check your coding notice first - it usually explains exactly why your code is what it is.
• Overpaid or underpaid? HMRC refunds overpayments and spreads underpayments across future pay. You won't lose out long-term.

Don't Leave Your Tax Code to Chance

A wrong tax code quietly drains your pay packet or builds a bill you didn't see coming. Checking it takes minutes - but knowing whether it's actually right takes a bit more know-how, especially once savings interest, benefits, or multiple jobs come into play.

That's where Debitam comes in. Our team handles the fiddly bits - checking your code, spotting errors, and dealing with HMRC and Companies House so you don't have to sit on hold for 30 minutes on your lunch break. Accurate, fast, and refreshingly jargon-free.

Check your tax code today, and if anything looks off, get in touch with Debitam - we'll put it right before it costs you.

Frequently Asked Questions

Can I change my tax code myself?

No. Only HMRC can change your tax code. What you can do is give HMRC the correct information - through your Personal Tax Account, the HMRC app, or by phone - and they'll issue the corrected code to you and your employer.

How long does HMRC take to change a tax code?

HMRC aims to update your tax code and notify you and your employer within 15 working days. Your employer then applies the new code on your next pay day, so the change usually shows up within one pay cycle of HMRC processing it.

Will I get a refund if I've been on the wrong tax code?

Yes. If you've overpaid tax in the current year, the corrected code usually returns the extra through your wages. For previous tax years, HMRC sends a refund directly, often after issuing a P800 tax calculation.

How do I change my tax code from BR to 1257L?

If BR is on your only job (rather than a second job), contact HMRC on 0300 200 3300 or update your employment details in your Personal Tax Account. HMRC will reassign your full Personal Allowance and issue a 1257L code.

How do I get off an emergency tax code?

Complete your employer's starter checklist and make sure HMRC has your previous employment details (usually from your P45). Once HMRC has the full picture, they'll switch you to a normal cumulative code and refund any tax you overpaid.

Why did my tax code change without me doing anything?

HMRC now updates codes mid-year using information from third parties, such as banks reporting your savings interest or employers reporting benefits in kind. Log into your Personal Tax Account to see your coding notice, which explains exactly what triggered the change.