Medical reports are required to support court applications to appoint a deputy to make decisions on behalf of a person who has lost mental capacity. The doctor writing such a medical report needs to be able to systematically assess the mental capacity of the person in question, in order to gather the necessary evidence for the court to make a decision. If the medical report is not adequate, the application will be rejected and the appointment of the deputy delayed. This article sets out best practices for performing the assessment and writing the medical report, common errors, and issues of concern.