This paper argues that existing English and Welsh mental health legislation (The Mental Health Act 1983 (MHA)) should be changed to make provision for advance decision-making (ADM) within statute and makes detailed recommendations as to what should constitute this statutory provision. The recommendations seek to enable a culture change in relation to written statements made with capacity such that they are developed within mental health services and involve joint working on mental health requests as well as potential refusals. In formulating our recommendations, we consider the historical background of ADM, similarities and differences between physical and mental health, a taxonomy of ADM, the evidence base for mental health ADM, the ethics of ADM, the necessity for statutory ADM and the possibility of capacity based ‘fusion’ law on ADM. It is argued that the introduction of mental health ADM into the MHA will provide clarity within what has become a confusing area and will enable and promote the development and realisation of ADM as a form of self-determination. The paper originated as a report commissioned by, and submitted to, the UK Government's 2018 Independent Review of the Mental Health Act 1983.