[header] How to complete a self assessment tax return [title] Register this year if you didn't send in a tax return last year. [step] You may already be registered if you turned in a tax return last year. However, if you did not send in a self-assessment form last year, you'll need to register again this year. 
[substeps] Alternatively, if you have registered in the past and sent in a return last year, find the unique taxpayer reference (utr) number that was sent to you. You'll use this number when filing online.