Competence is an essential legal requirement for valid consent to medical treatment. Children under 16 may be considered ‘Gillick competent’ to make treatment decisions, but may need to demonstrate this. Applied tests for competence are wide-ranging and context dependent. Competence is related to cognitive ability and experience and may be enhanced by education, encouragement etc.; there is a general duty for professionals to enhance the competence of children in their care. The need to assess a child's competence may occur when s/he wishes to make a controversial decision whose wisdom others dispute. Potential assessors should have the necessary practical skills and an understanding of the child in their social and medical context. Assessments should be developmentally appropriate, explore systemic influences, and consider the child's emotional state, cognitive development and ability to balance risks and benefits. The involvement of a psychologist or other independent third party should be considered in cases that raise serious concerns about competency, or that involve complex decisions or conflict between the various parties. In rare cases courts may be involved.