There is an online tool, developed by HMRC, that allows taxpayers to check if they need to notify HMRC about additional income. The online tool can be found at www.gov.uk/check-additional-income-tax.

You are required to submit a self-assessment return if any of the following apply:

You may also need to send a tax return if you have any untaxed income, such as:

There could be other reasons why you may be required to register for self-assessment and therefore using HMRC’s online tool can help you check if you are required to submit a return.

Source:HM Revenue & Customs | 03-06-2024