If you dont already have a UTR number, you will need to get one from HMRC
You will automatically be sent a Unique Taxpayer Reference (UTR) when you:
• Register for Self-Assessment (Self-Employed)
• Set up a limited company
It is a 10-digit number. It might just be called ‘tax reference’.
Where to find your UTR
Your UTR is on previous tax returns and other documents from HMRC, for example:
• Notices to file a return
• Payment reminders
You can also find your UTR in your Personal Tax Account if you are registered for Self-Assessment.