What this tool does

It takes the tax code shown on your payslip or coding notice and tells you, in everyday language, what it actually means. You will see how much tax-free income the code gives you, what the letters stand for, and whether the code looks right for someone in your situation.

If something seems off, the tool points out what to check and how to get it corrected, so you are not left guessing whether HMRC has the right information about you.

When to use it

It is useful any time your tax code changes, when you start a new job, take on a second job, or begin drawing a pension. It is also worth a look if your take home pay has shifted without explanation, or if you have received a P2 coding notice in the post and are not sure what it is telling you.

The tool is aimed at employees, pensioners, and people with more than one source of PAYE income. It is not built for self assessment calculations, but it will help you understand the code that sits behind your PAYE deductions, which is often where overpayments and underpayments start.

How it works

Type your tax code into the box, add a few details about your income and circumstances if asked, and you will get a short written explanation covering what the code means, whether it looks sensible, and the steps to take if you think it is wrong. Nothing you enter is saved, and you do not need to sign up or share personal details like your National Insurance number.

If the explanation suggests your code might be incorrect, the next step is usually to contact HMRC directly or check your personal tax account online. The tool will flag this where relevant, but it does not contact HMRC on your behalf. Think of it as a quick second opinion that helps you ask the right questions before you pick up the phone.