1229 - Unique taxpayer reference
A Unique Taxpayer Reference (UTR) will have been issued by HM Revenue & Customs when registering the Self Assessment account. It is made up of 10 numbers eg 1234567890. You will find it on a Tax Return (SA100), a Notice to complete a Tax Return (SA316) or on a Statement of Account. It may also be on other documents.
Where to find this