A UTR, or Unique Taxpayer Reference, is a 10-digit number that HMRC assigns to you when you register for Self Assessment. It is unique to you and stays with you for life, even if you change jobs or move house. Think of it like a personal ID number just for your taxes. HMRC uses it to track your tax records and make sure your payments and returns are matched to the right account. You will need it every time you deal with HMRC, whether that is filing a tax return, paying tax, or calling them for support.
