What's a UTR number and how do I get one?

A UTR (Unique Taxpayer Reference) is a 10-digit number that HMRC uses to identify you in the Self Assessment system. You get one when you register, and it stays the same for the rest of your life. You need your UTR to file your return, contact HMRC about your tax affairs, or appoint an accountant to act on your behalf. To register and get a UTR, go to GOV.UK and search 'register for Self Assessment'. Once registered, HMRC sends your UTR by post within about 10 working days.