What is a UTR number?

What a UTR number means

A Unique Taxpayer Reference (UTR) is a 10-digit number HMRC uses to identify a taxpayer. Individuals get one when they register for Self Assessment, for example when they become a sole trader, a partner, a landlord or a company director with untaxed income. Every limited company also has its own company UTR for Corporation Tax, sent to its registered office shortly after incorporation.

A personal UTR and a company UTR are separate numbers. A director who owns a company will usually have both, and mixing them up is one of the most common reasons a return is rejected.

Example

Tom leaves his job in May to go freelance. He registers for Self Assessment by 5 October following the end of the tax year. HMRC posts a letter (form SA250) with his 10-digit UTR, which may be written with a K on the end in some HMRC systems, such as 12345 67890K. He gives the number to his accountant, who uses it to file his tax return and set up his payments, which are referenced with the UTR followed by K.

Where to find it

• Your Self Assessment registration letter or previous tax returns
• Payment reminders and statements from HMRC
• Your HMRC online account or the HMRC app
• For companies, the letter HMRC sends after incorporation, or the company's Corporation Tax online account

Why it matters for your business

Without a UTR you cannot file a tax return, so late registration can quickly lead to late filing penalties. Contractors in the construction industry also need one so their contractor can verify them under CIS at the 20% rate rather than 30%.

Our full guide to the UTR number covers how to get one, how long it takes and what to do if you have lost yours.