To register as self-employed you can head to the government's online registration portal, and start the registration process.
Here’s some of the information needed for the registration
· Date the business started
· Personal details, including National Insurance number and home address
· Details about the jobs the business does
After the registration has been completed, you will need to wait up to 10 days while HMRC processes the information. During this time HMRC will send out a letter that includes your Unique Taxpayer Reference (UTR) which is a 10-digit code, that will be used when completing the Self-Assessment. HMRC will also create an online account, which will give access to different digital governmental services.