Unique Taxpayer Reference (UTR)
Your UTR is a ten-digit number in the format 1234567890. If you are already
registered for Self Assessment, you will find your UTR on the front page of
your tax return or any Self Assessment calculations HM Revenue & Customs
(HMRC) have sent you.
If you are completing the form on behalf of a company, you should enter the
company’s UTR if it has one. This will be shown on correspondence from HMRC.