UK Tax Codes Explained 2026/27 — What Your Code Means and How to Fix It

Your tax code is a short string of numbers and letters on your payslip that tells your employer how much income tax to deduct under PAYE (Pay As You Earn). For most UK employees in 2026/27 it is 1257L — but millions of people each year have the wrong code applied without realising it, leading to overpaid or underpaid tax.

Getting your tax code wrong can cost you hundreds of pounds. A BR code (emergency rate, no Personal Allowance) applied to your main job will overtax every penny you earn. A K code inflating your taxable income means you pay tax you may not owe. Understanding what your code means — and how to fix it — is one of the most useful things you can do to protect your take-home pay.

How Your Tax Code Works

Under PAYE, your employer does not decide how much tax to deduct — HMRC does, via your tax code. The code contains two pieces of information:

1. The number — multiply by 10 to get your tax-free income for the year. Code 1257 = £12,570 tax-free.
2. The letter — tells your employer what rules apply (standard allowance, emergency rate, higher rate, negative allowance, and so on).

Your employer feeds the code into their payroll software and HMRC’s tables do the rest. Each pay period, they calculate what tax is due on your cumulative income that tax year, subtract what you have already paid, and deduct the difference.

What Each Tax Code Letter Means

How the Number in Your Code Is Calculated

The number is not always 1257. HMRC adjusts it to account for your specific circumstances:

Additions that increase the number (increase your tax-free income):

• Working from home allowance (if HMRC has approved it)
• Job-related expenses (professional subscriptions, uniform costs)
• Marriage Allowance received from a spouse

Deductions that reduce the number (reduce your tax-free income):

• Taxable employment benefits such as a company car or private medical insurance (the benefit value is coded in, meaning you pay tax on it through PAYE rather than via Self Assessment)
• State Pension income above the Personal Allowance
• Underpaid tax from a previous year being collected gradually

Example: An employee with a £12,570 Personal Allowance but a company car with a benefit-in-kind value of £4,000 would have a code of approximately 857L — their allowance is reduced by £4,000 to collect the tax due on that benefit throughout the year.

K Codes: What They Mean and What to Do

A K code appears when the deductions HMRC wants to make through PAYE exceed your Personal Allowance entirely. Rather than reducing your tax-free income, a K code adds to your taxable income.

K400 means an extra £4,000 is added to your taxable pay before tax is calculated. On a £30,000 salary with K400, you would pay income tax as if you earned £34,000.

K codes are most common when:

• Your company car or private medical benefit is worth more than your remaining allowance
• Underpaid tax from a previous year is being recovered (HMRC can spread this over up to three years)
• You receive a taxable State Pension that exceeds your Personal Allowance

Important protection: Employers cannot deduct more than 50% of your gross pay in a single pay period under a K code. If the notional tax due would exceed half your pay, the deduction is capped automatically.

If you receive a K code unexpectedly, log into your HMRC Personal Tax Account to see exactly what is driving it. Common errors include HMRC carrying forward a benefit that no longer applies, or applying the wrong value for a company car.

Tax Codes When You Have Multiple Jobs or Pensions

If you have more than one source of PAYE income, you will typically have a different code for each:

• Main job or pension: 1257L (your full Personal Allowance)
• Second job or additional pension: BR (20%) or D0 (40%), depending on which tax band your second income falls into

You can ask HMRC to split your allowance differently across your jobs if you prefer — useful if your second job is regular enough that splitting the allowance reduces overpayment. Contact HMRC via your Personal Tax Account to request this.

If your total income across all sources takes you into the higher or additional rate, HMRC may also adjust the number in your main code downwards to collect the extra tax.

Scottish and Welsh Tax Codes

If you live in Scotland, your code has an S prefix (S1257L). This tells your employer to apply Scottish income tax rates, which differ from the rest of the UK:

• Scotland has six tax bands in 2026/27, with the higher rate starting at £43,663 (compared to £50,270 in England, Wales, and Northern Ireland).
• At a salary of £50,000, a Scottish taxpayer pays around £1,550 more in income tax than an equivalent English taxpayer.

If you live in Wales, your code has a C prefix (C1257L). Welsh income tax rates currently match England’s, so the practical effect is minimal — but the prefix ensures HMRC directs the tax revenue to the Welsh Government.

If you move between Scotland, Wales, and England, HMRC updates your prefix based on your home address. If you move and do not update your address, you may end up on the wrong code.

How to Fix a Wrong Tax Code

1. Check your current code — look at your payslip or log into your HMRC Personal Tax Account
2. Identify the error — compare the number against your expected Personal Allowance and check for any benefits or previous-year adjustments you do not recognise
3. Report the error — in your Personal Tax Account, go to ‘Check your income tax’ and update your employment or benefit details. Alternatively, call HMRC on 0300 200 3300
4. HMRC issues a new code — usually within a few days; your employer’s next payroll run will use the corrected code
5. Overpaid tax is refunded — if you have paid too much, HMRC will either adjust your code to refund it through future pay periods, or issue a refund by cheque or bank transfer after the tax year ends

You have four years from the end of a tax year to claim a refund for an overpayment — so if you discover you had the wrong code in 2023/24, you can still reclaim that tax.

Articles in This Cluster

• Tax Codes Explained UK — the complete reference guide to every code type
• Understanding Your Tax Code — what the number and letter mean for your specific situation
• Can I Change My Tax Code? — when and how to request a change from HMRC
• Why Has My Tax Code Changed? — common reasons your code is different this year
• What Happens If You Get the Wrong Tax Code? — consequences for overpaid and underpaid tax
• Tax Code Checker Guide — step-by-step verification using the HMRC Personal Tax Account
• Emergency Tax Explained — BR and W1/M1 codes, why they happen, and how to get a refund
• Why Am I Paying Emergency Tax? — the most common triggers and how to resolve them quickly
• Tax Code on Unpaid Leave — what happens to your code and your take-home pay when you take unpaid leave
• P45 Explained — what it is, when you get it, and what to do if you lose it
• P60 Explained — your annual tax summary: why it matters and when you need it

Related Hubs

• Income Tax Guide — rates, allowances, and how PAYE works
• Self Assessment Hub — filing a tax return, claiming refunds, and dealing with HMRC
• Take-Home Pay Calculators — see your actual net pay at any salary after tax and NI
• National Insurance Hub — how NI contributions work alongside your tax code