Under the 1983 Act, the patient’s mental capacity or competence to consent to or refuse treatment is expressed by reference to whether the patient is "capable of understanding the nature, purpose and likely effects" of that treatment. In clinical practice, this is understood to refer to capacity or competence. This position is confirmed in the Code of Practice. Section 20 amends this wording to references to ‘capacity or competence to consent’. While this amendment is not expected to create a practical change in clinical approaches to assessing capacity or competence, this change provides clarity by confirming the shared legal concepts between the 1983 Act and the Mental Capacity Act 2005 Act (the 2005 Act). It also brings Part 4 in line with Part 4A of the 1983 Act, which already adopts this terminology.
	Subsection (6) provides that references in Part 4 of the 1983 Act to "capacity" are applicable to patients who are aged 16 or older, references to "competence" are applicable to patients under the age of 16.
	Subsection (6) also clarifies that references to an advance decision made by a patient are within the meaning of the 2005 Act. References to "valid and applicable", in relation to an advance decision, means valid and applicable to the treatment in question in accordance with section 25 of the 2005 Act. References to a "donee" are to a donee of a lasting power of attorney created by the patient, within the meaning of section 9 of the Mental Capacity Act 2005, where the done is acting within the scope of their authority and in accordance with that of the Mental Health Act 1983. References to a "deputy" are to a deputy appointed for the patient by the Court of Protection under section 16 of the 2005 Act, where the deputy is acting within the scope of their authority and in accordance with that Act. By cross referencing the Mental Capacity Act 2005, the Mental Health Act 2025 gives recognition to pre-existing and well-established concepts that seek to provide people with the power to inform their future care and treatment, in case at a later date they are too unwell and lack the capacity to make treatment decisions.
Treatment Section 20: Capacity to consent to treatment