The Mental Capacity Act 2005: what it does and who it covers

What is the Mental Capacity Act 2005?

It's the law in England and Wales for people who lack capacity to make a decision for themselves. It received Royal Assent on 7 April 2005, and its core sections came into force on 1 October 2007. It also made the Court of Protection a superior court of record.

It answers three questions. Can this person make this decision now? If not, who decides, and how? And what protects the people who act for them, and the person themselves?

Who does the Mental Capacity Act apply to?

Anyone aged 16 or over who may lack capacity for a particular decision (s2(5)). Lasting powers of attorney (s9), advance decisions (s24) and statutory wills (s18(2)) need the person to be 18, and so does DoLS (Sch A1 para 13).

It applies to everyone who acts for them, family carers included. Professionals and paid carers must also have regard to its Code (s42(4)).

The MCA and dementia, learning disability and mental illness

A diagnosis never settles capacity. You can't establish a lack of capacity merely from someone's age, appearance, condition or behaviour (s2(3)). Don't let a label such as dementia, learning disability or schizophrenia stand in for an assessment.

The question is always this decision, at the time it needs making, decided on the balance of probabilities (s2(1) and (4)). Capacity can fluctuate, so record when you assessed and why (JB [64]).

What the Act lets you do, and what it doesn't

• It protects reasonable care. Take reasonable steps to assess capacity, and reasonably believe they lack it and that the act is in their best interests. Then you're protected as if they'd consented, though not for negligence (s5).
• It limits restraint. Restraint must be necessary to prevent harm to them, and proportionate to how likely and serious that harm is (s6).
• It lets people plan ahead. Attorneys and advance decisions can bind you, so check for both before a big decision (ss9 to 14 and 24 to 26).
• It has decisions nobody can make. No one can consent for someone to marriage, sex, divorce or adoption, among others (s27).
• It isn't an MHA substitute. It can't authorise treatment for mental disorder that Part 4 of the MHA regulates (s28).

How it fits with the Mental Health Act

The MHA can treat mental disorder whatever the patient's capacity. The MCA works only where someone lacks capacity, and then only in their best interests. An objecting patient who meets s2 or s3 and needs hospital treatment for mental disorder can't be put on DoLS, so the MHA it is (Sch 1A; GJ).

For a patient who lacks capacity and doesn't object, both may be available. The MHA Code says choose on the facts, not out of habit, and record why (MHA Code 13.58 and 13.60). MHA or MCA? takes you through it.

The Code of Practice and other guidance

The Lord Chancellor issues the Code under s42. Attorneys, deputies, IMCAs, researchers, and anyone acting professionally or for pay must have regard to it (s42(4)). Courts must take a relevant provision, or a failure to follow it, into account (s42(5)).

It's guidance, not instruction, but if you don't follow it you'll be expected to give good reasons (MCA Code introduction). Family carers aren't legally bound by it, though they should follow it as far as they know it. NICE's guideline NG108 (2018) covers decision-making and capacity in practice.

What's changing

AGNI changed the meaning of deprivation of liberty on 2 June 2026, with immediate effect. DoLS still applies where someone is deprived of liberty, but DHSC expects far fewer authorisations in the long run. See deprivation of liberty after AGNI.

The Liberty Protection Safeguards, legislated in 2019 to replace DoLS, aren't in force. The consultation promised for the first half of 2026 hasn't appeared, and a revised MCA Code is tied to it. DHSC says it's still assessing what AGNI means for LPS.