For those unfamiliar with Self-Assessment or uncertain about the need to file a return, this article provides guidance. Typical reasons involve being self-employed, earning over £100,000, or having income from sources not subject to taxation. Inform HMRC by the 5th of October 2023, for the 2022/23 tax year. The article recommends using HMRC's online tool for clarification and outlines various scenarios that require filing. Seek professional advice if you're uncertain.