Millions of taxpayers are being urged to take just seconds to check a crucial detail that could mean they are paying too much tax – or facing an unexpected bill later.

HMRC has issued a fresh “check it” alert, warning that an incorrect tax code can quietly eat into your income or leave you owing money. In a post to social media, the tax authority said: “Think your tax code might be wrong? Check it in seconds with the HMRC app and avoid paying too much or too little. Download the app today.”

Why your tax code matters

Your tax code determines how much Income Tax is taken from your wages or pension. If it is wrong, you could:

• Overpay tax, reducing your take-home pay
• Underpay tax, storing up a bill for later

Errors can creep in for a number of reasons – including changing jobs, having more than one income, or receiving workplace benefits such as a company car.

‘Quick and easy’ check

HMRC says its official app offers a fast way to review your details without needing to call or write in.

According to government guidance, the app allows users to:

• Check their tax code and income details
• View National Insurance contributions
• Access information about benefits and tax credits
• See messages and updates from HMRC

The guidance describes the app as a “quick and easy way” to stay on top of your tax affairs.

Download links

Brits can download the HMRC app using the official links below:

Apple App Store.

Google Play Store.

How to access your details

To use the app, you will need to sign in using your Government Gateway ID. If you do not have one, you can create it during the setup process.

HMRC has increasingly pushed taxpayers towards digital services, with the app becoming a central tool for checking records and avoiding mistakes.

Why acting now could pay off

With millions of workers seeing pay changes, job moves or benefit adjustments each year, tax codes can quickly fall out of date.

A quick check now could mean:

• A refund if you’ve overpaid
• Avoiding a surprise tax demand later

For many, it is one of the simplest ways to ensure they are not losing money unnecessarily — or being caught out by an unexpected bill.