Tax Code Checker UK

Your tax code is one of the most important numbers on your payslip, and one of the least understood. It tells your employer how much tax-free income you're entitled to before deductions begin, and if it's wrong, you'll either overpay tax month after month or quietly build up a bill that HMRC will eventually come for. Millions of tax codes are adjusted every year, and errors are far from rare, so it's worth knowing how to read yours.

How to read a tax code

Most tax codes are a number followed by a letter. The number is your tax-free Personal Allowance divided by 10, and the letter describes your situation. The standard 2026/27 code, 1257L, means:

• 1257 — a tax-free allowance of £12,570 for the year
• L — you're entitled to the standard Personal Allowance

In Scotland the same code appears as S1257L, and in Wales as C1257L, reflecting devolved Income Tax rates and bands (Wales currently mirrors England and Northern Ireland; Scotland has its own bands).

What the letters mean

K codes explained

A K code works in reverse. Instead of having tax-free income, you owe tax on more than you earn from this source, usually because of company benefits like a car, or underpaid tax from a previous year being collected through your code. A code of K475, for example, means £4,750 is effectively added to your taxable income for the year. There's a safeguard: no more than half of your pre-tax pay in any period can be taken in tax under a K code.

Why your code changes

HMRC adjusts codes when your circumstances change, common triggers include:

For deeper guides, see our tax codes and what they mean, 1257L guide, why tax codes change, checking and correcting HMRC tax codes, UK tax codes explained, and why codes move from 1250L to 1185L.

• Starting or leaving a job, or taking a second one
• Receiving a company benefit for the first time, or giving one up
• Claiming Marriage Allowance
• Underpaying or overpaying tax in a previous year, collected or refunded via your code
• Starting to receive a pension or taxable state benefits
• Income rising above £100,000, where the Personal Allowance tapers away at £1 for every £2 above the threshold, disappearing entirely at £125,140

How to check yours is right

Compare your code against your actual circumstances. Ask yourself: do I have one job or several? Any company benefits? Have I claimed Marriage Allowance? Did I over or underpay last year? Your personal tax account on gov.uk shows how HMRC has calculated your code, broken down line by line, and lets you report anything that's out of date, for example a company car you no longer have.

If your code is wrong, don't leave it. Overpayments are your money sitting with HMRC, and underpayments accumulate into a bill. Codes can be corrected mid-year, and PAYE's cumulative design means a correction usually squares things up in your next payslip or two.

No uplift for 2026/27

Because the Personal Allowance remains frozen at £12,570, HMRC issued no automatic uplift of tax codes for 2026/27, the standard code carried over unchanged. Frozen thresholds mean more people drift into higher bands as wages rise, which makes checking your code more worthwhile, not less.

This is general guidance, not financial advice. For your exact code and how it was calculated, check your personal tax account on gov.uk or contact HMRC.