A guide to registering for Self-Assessment

If you’ve never had to complete a self-assessment tax return, the first time can be daunting. But don’t worry: we’ll demystify the process in this article. And if you have completed one before, this guide might still teach you a thing or two about doing your self-assessment better.


Self-assessment is the way millions of people in the UK report and pay their taxes. Specifically, 11.7 million people filed their tax return via self-assessment for the 31 January deadline in 2023.

As the name suggests, self-assessment is all about the taxpayer assessing their own tax liabilities by telling HMRC about their financial activities and income via form SA100. HMRC then uses that reported income to work out how much tax and National Insurance contributions (NICs) you need to pay.

guide to registering for self-assessment