On January 31st you are required to submit your Self Assessment form. There are a couple of ways you can do this.
- With the user ID and password you got when you registered for Self Assessment, sign in to your HMRC online account, fill in the form and send it directly from there: https://www.gov.uk/log-in-file-self-assessment-tax-return
- You can also submit the paper form by post to:
HM Revenue and Customs