Posted March 5, 2025

How Do You Check Your Tax Code?

Introduction

Your tax code may look like a random assortment of numbers and letters, but it significantly impacts how much tax you pay each month. At Whitesides Chartered Accountants, we regularly help clients discover they’ve been assigned incorrect tax codes.

This straightforward guide explains how to check your tax code, understand what it means, and what to do if you think it’s wrong.

What is a Tax Code?

Your tax code is used by your employer or pension provider to calculate how much income tax to deduct from your pay or pension. It essentially tells them how much tax-free income you’re entitled to.

A typical tax code consists of several numbers followed by a letter. For example, the standard tax code for 2024/25 is 1257L, which means you can earn £12,570 before paying any income tax.

Where to Find Your Tax Code

Your tax code appears in several places:

Payslip: Look for a section called “Tax Code” or “PAYE Code” on your payslip
P60: The end-of-year certificate you receive from your employer
P45: The form you get when you leave a job
Pension statement: If you receive a pension
HMRC Personal Tax Account: Online through the HMRC website
Annual Tax Code Notice: The letter HMRC sends (usually between January and March) showing your tax code for the upcoming tax year

How to Check Your Tax Code Online

The easiest way to check your tax code is through your HMRC Personal Tax Account:

Visit gov.uk/personal-tax-account
Sign in using Government Gateway or create an account if you don’t have one
Select “Check your Income Tax”
Under “PAYE”, you’ll see your current tax code(s) for each employment or pension

Understanding What Your Tax Code Means

The Numbers

The numbers in your tax code represent the amount of tax-free income you’re entitled to in that tax year, divided by 10.

For example:

1257L means you have a tax-free allowance of £12,570
300L would mean you have a tax-free allowance of £3,000

The Letters

The letter at the end of your tax code provides additional information about your tax situation:

L: You’re entitled to the standard tax-free Personal Allowance
M: Marriage Allowance – you’ve received 10% of your partner’s Personal Allowance
N: Marriage Allowance – you’ve transferred 10% of your Personal Allowance to your partner
T: Your tax code includes other calculations to work out your Personal Allowance
0T: Your Personal Allowance has been used up, or you’ve started a new job and don’t have a P45
BR: All your income from this source is taxed at the basic rate (20%)
D0: All your income from this source is taxed at the higher rate (40%)
D1: All your income from this source is taxed at the additional rate (45%)
K: Your total deductions exceed your allowances (often due to taxable state benefits or company benefits)
W1 or M1: Emergency tax codes, used when HMRC doesn’t have enough information about your income

Common Tax Codes and What They Mean

Here are some common tax codes you might see:

1257L: The standard tax code for 2024/25 (£12,570 Personal Allowance)
BR: All income taxed at basic rate – often used for second jobs
0T: No Personal Allowance – may be used if you earn over £125,140
NT: No tax to be deducted – rare but used for specific situations
K: Indicates that deductions exceed your allowances
S1257L: Scottish taxpayer with standard Personal Allowance
C1257L: Welsh taxpayer with standard Personal Allowance

Why Your Tax Code Might Be Wrong

Tax codes can be incorrect for many reasons:

You’ve changed jobs during the tax year
You have multiple jobs or pensions
You receive taxable benefits (company car, medical insurance, etc.)
You’ve started receiving the State Pension
You claim tax relief for work expenses or professional subscriptions
HMRC has estimated your taxable benefits or untaxed income incorrectly
An underpayment from a previous year is being collected
Your circumstances have changed, but HMRC hasn’t updated their records

Signs Your Tax Code Might Be Incorrect

Consider checking your tax code if:

It’s changed unexpectedly
You have multiple jobs but only one tax code shows the full Personal Allowance
You’ve recently started receiving a pension
You receive taxable benefits from your employer
Your code includes ‘W1’ or ‘M1’ and has been that way for more than three months
Your take-home pay seems unusually high or low
You’ve recently changed jobs

How to Query Your Tax Code

If you think your tax code is wrong:

Contact HMRC directly:

Phone: 0300 200 3300
Have your National Insurance number ready

2. Use your Personal Tax Account:

Log in at gov.uk/personal-tax-account
Select “Check your Income Tax”
Choose “Tell us about a change”

3. Write to HMRC: Pay As You Earn and Self-Assessment HM Revenue and Customs BX9 1AS

What Happens If Your Tax Code Is Wrong

If you’ve paid too much tax: HMRC will usually refund you automatically, either by adjusting your tax code or sending a refund by cheque
If you’ve paid too little tax: HMRC typically collects underpaid tax by adjusting your tax code for the following tax year, spreading the payments

How We Can Help

At Whitesides Chartered Accountants, we can:

Review your tax code to ensure it’s correct
Help you understand what your tax code means for your specific situation
Assist with contacting HMRC to resolve any issues
Identify potential tax refunds you may be entitled to
Ensure your tax affairs are structured efficiently going forward

Next Steps

It’s worth checking your tax code at least once a year, particularly if your circumstances change. If you’d like a professional review of your tax code and overall tax position, please contact us on 0113 2582437 to arrange a no-obligation discussion.

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