How to Check Your Tax Code Is Correct (UK)

Slug: how-to-check-your-tax-code-is-correct-ukPillar: Business and Finance > Financial PlanningKeyword: check tax code correctExcerpt: Millions of UK workers are on the wrong tax code right now. Here's how to check yours in five minutes and claim back what you're owed.

If a chunk of your paycheck has been vanishing into tax you didn't actually owe, you're not alone. Somewhere between 5 and 6 million people in the UK are walking around on the wrong tax code right now, and most of them have no idea. Checking yours takes about five minutes and could put real money back in your account.

What a tax code actually does

Your tax code tells your employer or pension provider how much of your income is tax-free before they start deducting anything. Get it wrong, and you either overpay (common) or underpay (which HMRC will eventually claw back, sometimes in one lump sum). The standard code for most people in 2026/27 is 1257L, which reflects the standard Personal Allowance of GBP12,570 – the amount you can earn each year before Income Tax kicks in. That allowance is frozen until April 2028, according to GOV.UK, so it isn't going up anytime soon.

The letters after the number matter too. An L means you get the standard allowance. A K code means you have income that isn't being taxed elsewhere – company car, unpaid tax from a previous year – and it's being collected through your pay. BR means all your income from that job is taxed at the basic rate with no personal allowance at all, which is common if you have two jobs or a new one. Then there's the pair everyone dreads: W1 and M1, the 'emergency' non-cumulative codes.

How emergency tax codes catch people out

If you start a new job and don't hand over your P45, or you go from self-employed to salaried, your new employer often has no history for you. So they tax you on an emergency code – W1 for weekly pay, M1 for monthly. Per GOV.UK, this means you're taxed only on what you earn in that single pay period, treated as if you'd earn that same amount every week or month of the year, with no account taken of allowances you've already used or income from earlier in the tax year. It usually overtaxes you, sometimes by a lot, until HMRC sorts out your real code.

The fix is simple: if you have a P45 from your last job, give it to your new employer immediately. If you don't, fill in HMRC's new starter checklist. Either one gets you off the emergency code faster.

How to check your code in five minutes

• Look at your last payslip. Your tax code sits right next to your gross and net pay figures.
• Check your P2 coding notice, the letter HMRC sends before the tax year starts explaining how your code was worked out.
• Log into your Personal Tax Account at gov.uk/check-income-tax-current-year. This shows your current code, what it's built from, and an estimate of tax owed for the year – and it's free, no accountant needed.

Compare what you find against 1257L (or S1257L if you're a Scottish taxpayer, C1257L in Wales). If your situation is simple – one job, no benefits in kind, no other income – and your code isn't 1257L, something's likely off.

Common reasons your code is wrong

HMRC bases your code on the information it has, and that information goes stale fast. A few of the usual culprits:

• You changed jobs mid-year and your old employer's figures never updated properly.
• You're still being taxed for a company benefit – a car, private medical cover – that you no longer receive.
• You have two income sources and both are applying a full personal allowance, which isn't allowed.
• An estimate from a previous year got carried forward without being corrected.

This isn't a rare glitch. An FOI request by accountancy firm UHY Hacker Young, reported widely in the UK press in early 2026, found around 5.6 million people overpaid a combined GBP3.5 billion in Income Tax during the 2023-24 tax year because of incorrect PAYE tax codes. Separate figures for 2024-25 put the number of people on an incorrect code at over 6 million. Whichever year you look at, the pattern holds: this happens to millions of ordinary PAYE employees every single year, not just the unlucky few.

What to do if your code is wrong

Don't wait for HMRC to catch it – reach out yourself. You can update your details or query your code directly through your Personal Tax Account, via the HMRC app, or by phone on 0300 200 3300. Have your National Insurance number and recent payslip ready before you call; it moves things along.

If you've been overpaying, HMRC will usually correct your code going forward and refund the difference either automatically through your pay or as a direct payment. If you've underpaid, your code will be adjusted so the extra owed is collected gradually – normally spread over the following tax year rather than taken as one shock deduction. Either way, sorting it early beats discovering a surprise bill two years down the line.

One thing worth knowing: if your income is above GBP100,000, your Personal Allowance starts shrinking – it drops by GBP1 for every GBP2 you earn over that threshold, reaching zero at GBP125,140, per GOV.UK. If you're near that band, it's worth checking your code more carefully than most, since small errors compound.

The five-minute habit worth keeping

Realistically, checking your tax code once a year – ideally right after April when new codes are issued, or whenever you change jobs – is enough to catch most problems before they snowball. It's not glamorous. But it's one of the few financial checks that costs nothing, takes minutes, and can hand you back money you already earned.

For more on getting your everyday finances in order, see our guides on <a href="https://eight2infinity.com/pillar/business-and-finance">building better money habits</a> and <a href="https://eight2infinity.com/pillar/business-and-finance/financial-planning">financial planning basics</a>.

FAQ

How do I find my tax code quickly?

Check your most recent payslip – it's printed next to your pay details – or log into your Personal Tax Account at gov.uk to see it instantly.

What does tax code 1257L mean?

It means you get the standard GBP12,570 tax-free Personal Allowance for the 2026/27 tax year, with no adjustments or deductions.

Why am I on an emergency tax code?

Usually because a new employer doesn't yet have your full income history. Handing over your P45 or completing the new starter checklist usually fixes it within a pay cycle or two.

Can I get a tax refund if my code was wrong?

Yes. If HMRC confirms you overpaid, you'll typically get the refund automatically through your pay, or as a direct payment if you've already left that job.

Is this article financial advice?

No. This is general information based on current GOV.UK guidance, not personalised financial or tax advice. For anything specific to your situation, contact HMRC directly or speak with a qualified accountant.