Your UTR is on documentation isued by HMRC such as the 'tax return' (SA100), a 'Notice to complete a tax return' (SA316) or a 'Statement of account' (SA300). Depending on the type of document issued the reference may be printed next to the headings 'Tax Reference', 'UTR' or 'Our reference'. See example: https://www.zaptax.co.uk/question-help-images/utr.jpg
