Unique taxpayer reference (UTR)

Definition

A unique taxpayer reference (UTR) is a 10-digit number issued by HMRC to identify an individual or business within the UK tax system. It is unique to you or your company and stays the same for life, even if your circumstances change.

What it means

HMRC uses the UTR to track your tax obligations and records. You’ll be assigned a UTR when:

• You register for self-assessment as a sole trader or partner,
• You set up a limited company (the UTR is then linked to the company, not you personally), or
• You otherwise fall into the scope of self-assessment.

The UTR will appear on HMRC correspondence, including your self-assessment returns, payment reminders, and official tax notices. You’ll need to provide this code when completing online returns, speaking with HMRC about your tax affairs, or when your accountant or adviser is managing your filings.

Why it matters

The UTR is essential for ensuring that HMRC links all of your tax records correctly. Without it, you won’t be able to:

• Submit a self-assessment tax return
• Pay the right amount of tax
• Or authorise a third party (such as an accountant) to act on your behalf.

Because it is sensitive personal information, you should keep your UTR secure and avoid sharing it unnecessarily.

Example

If you register as self-employed in October 2025, HMRC will send you a letter (known as a SA250 – Welcome to Self Assessment) confirming your 10-digit UTR. From that point onwards, you must quote this number whenever you complete your annual tax return or deal with HMRC about your self-employment income. Similarly, if you form a limited company, Companies House notifies HMRC, and HMRC issues a UTR to the company shortly afterwards.