The Mental Capacity Act 2005, applicable to England and Wales only, was introduced to empower and protect people who are unable to make their own decisions. The act emphasises the importance of assuming a person has capacity to make decisions unless proven otherwise and recognises that people should be able to make seemingly unwise decisions. This article aims to provide an understanding of the Mental Capacity Act 2005, to support practitioners in undertaking and documenting capacity assessments. It presents a case study involving a young man with learning disabilities living in a care home under Deprivation of Liberty Safeguards (DoLS), in which an issue arose about his capacity to decline a healthcare procedure. It explains the process that was used to assess his capacity to make this decision, and what actions were subsequently taken. The article concludes by outlining the changes made by the Mental Capacity (Amendment) Act 2019, including the introduction of Liberty Protection Safeguards, which are due to replace DoLS in April 2022.