Google в помощь: it’s your first time registering
Register through your business tax account for Self Assessment and Class 2 National Insurance.
You’ll need a Government Gateway user ID and password to sign in. If you do not have a user ID, you’ll be able to create one.
You’ll get your Unique Taxpayer Reference (UTR) by post in 10 working days (21 days if you’re abroad). You’ll get it sooner in your personal tax account or HMRC app.
You’ll get a reminder letter or email telling you to complete a Self Assessment tax return before it’s due.