Your UTR can be found in several places. The easiest is to log into your HMRC online account, where it is displayed on your personal tax account page. If you have previously filed a tax return, it will be printed on the paper return or any letters HMRC has sent you. It also appears on your SA302 tax calculation and on your notice to file a return. If you cannot find it anywhere, you can call HMRC on 0300 200 3310 and they can confirm it after verifying your identity.