The five principles
Section 1 of the , and the first thing an examiner will ask you.
What is the Mental Capacity Act 2005?
The Mental Capacity Act 2005 sets the rules for decisions about people aged 16 and over who may lack capacity to make a particular decision. It applies in England and Wales, and most of it came into force on 1 October 2007.
It answers two questions. Can this person make this decision now (ss2 and 3)? If not, how should others act for them (s4 best interests, s5 protection from liability)? The five principles in section 1 govern all of it.
The Code of Practice dates from 2007 and has never been revised. Where it conflicts with later case law, follow the case law. The order of the capacity test is the main example. For the Act as a whole, see the Mental Capacity Act 2005.
How many principles are in the Mental Capacity Act?
Five. The first three protect the right to make your own decisions. The last two govern what others do once someone lacks capacity.
| What section 1 says | What it means in practice | |
|---|---|---|
| 1. Presume capacity | Assume capacity unless it's established that they lack it (s1(2)) | The person doesn't have to prove anything. The burden sits with whoever says they lack capacity. |
| 2. Support first | They're not unable to decide until all practicable steps to help have failed (s1(3)) | Find the right time, place, format and people before you conclude anything. |
| 3. Unwise isn't incapable | An unwise decision alone doesn't make them unable (s1(4)) | Disagreeing with you isn't evidence. A run of risky or out-of-character choices can be a reason to assess (Code 2.11). |
| 4. Best interests | Anything done for someone who lacks capacity must be in their best interests (s1(5)) | Their interests, seen from their side, not the team's or the family's. |
| 5. Less restrictive option | Consider whether the purpose can be met as effectively with less restriction (s1(6)) | It's a duty to consider. The best option isn't always the least restrictive one (Code 2.16). |
The presumption of capacity has limits
The presumption protects autonomy. It isn't a reason to look away. If there's legitimate doubt about someone's ability to make a decision, especially one with serious consequences, assess it.
A note saying 'there's a presumption of capacity, so it was his choice' won't stand up when there was good reason for concern. The more serious the risk, the more you should record what you discussed and why you think they can take it.
The reverse also holds. Assessment can feel intrusive, so don't do it without a reason, and be ready to say what that reason was.
What triggers a mental capacity assessment?
- Behaviour or circumstances that cast doubt on their ability to make this decision (Code 4.35).
- Someone else's concern, such as a relative, a carer or another professional.
- A known condition affecting the mind or brain, where they've already been shown to lack capacity for other decisions.
- Unwise decisions that repeatedly put them at significant risk, or one that's obviously irrational or out of character (Code 2.11).
None of these proves incapacity. They tell you to look properly, starting with whether more information or support would let them decide for themselves (Code 4.36).
All practicable steps: helping someone decide
- Information. Have they got everything relevant, including every realistic option? Explain it in the way that suits them: simple words, pictures, or an interpreter (s3(2)).
- Time and place. Is there a time of day or a setting where they do better? Can the decision wait until they're more able (Code 4.36)?
- People. Would someone who knows them help, such as a relative, carer, advocate or speech and language therapist?
- No undue pressure. Give advice and information, but don't push them towards your preferred answer (Code 2.8).
- Support, not substitution. If they're simply following someone else's instructions, that's a best interests decision in disguise. Treat it as one.
The rules in brief
- Presume capacity unless it's established that they lack it.
- Help them decide. They aren't treated as unable until all practicable steps to help have failed.
- Unwise isn't incapable. A decision you disagree with isn't, on its own, a reason to find them incapable. One that's out of character may be a reason to assess.
- Best interests. Anything done for someone who lacks capacity must be in their best interests.
- Less restrictive. Before acting, consider whether the purpose can be achieved as effectively in a way that restricts their rights and freedom less.
Read more: MCA 2005, s1 · MCA Code of Practice 2007, chapter 2: The statutory principles
The capacity test
This decision, at this time. Then ask why.
Someone can lack capacity to manage their money and still decide perfectly well what to eat, or whether to see their family. So start by naming the decision, and work out what they'd need to understand to make it.
Then test the four abilities, and only after that ask why. If they can't make the decision, is that because of an impairment of, or a disturbance in the functioning of, the mind or brain? Write down what you asked and what they said. A note that only says "lacks capacity" won't help anyone later.
The two-stage capacity test, in the right order
Section 2(1) is a single test with two questions. First, is the person unable to make the decision for themselves? Second, if so, is that because of an impairment of, or a disturbance in the functioning of, the mind or brain?
In A Local Authority v JB [2021] UKSC 52 the Supreme Court said the questions are taken in that order (para 79). The Code (4.11) puts the diagnosis first. The Court of Appeal has since said the Code contradicts JB, so follow JB.
The order matters. Start with the diagnosis and it's easy to tick it off and assume it explains everything. Start with what they can't do and you can target help, and you then have to show the causal link.
How to assess capacity: step by step
- Name the decision precisely, with the realistic options. 'Lacks capacity' on its own means nothing in law.
- Note why you doubt their capacity for this decision now.
- Work out the relevant information, including the foreseeable consequences of each option and of not deciding (s3(4)). Agree it with colleagues first.
- Take all practicable steps to help: the right time, place, format and people (s1(3)).
- Explain what the assessment is for, then give the information. Check understanding in their own words, not with yes or no questions (Code 4.49).
- Test each ability: understand, retain, use or weigh, communicate. Failing any one is enough (s3(1)).
- If they can't decide, ask why. Show how the impairment causes the inability, not just that both are present (JB, para 78).
- Decide on the balance of probabilities (s2(4)) and write it up while it's fresh.
The four abilities in practice
- Understand. They need the salient points, not every detail. Judge it only after you've explained things in a way that suits them (s3(2)).
- Retain. Long enough to make the decision. Retaining it only briefly doesn't make them incapable (s3(3)). Notes or photographs can help (Code 4.20).
- Use or weigh. Can they apply the information to their own situation and balance it? Someone with anorexia may understand the risks of not eating, yet be unable to use them against the compulsion (Code 4.22). The weight they give each factor is theirs.
- Communicate. By any means. This limb is meant for a narrow group, such as people with locked-in syndrome. If someone is expressing a view but can't decide, record it as their wishes and feelings.
Diagnosis, insight and cognitive scores
A diagnosis can be strong evidence on the second question, and it needn't fit ICD-11 or DSM-5. A cognitive score can inform your view, but the legal test still has to be met (Code 4.50). Fluent speech and good manners don't prove understanding (Code 4.49).
Insight is a clinical idea and capacity is a legal one. Someone can lack insight into their illness and still make a particular decision. If you rely on poor insight, say exactly how it stops them using or weighing the information.
Capacity also isn't one of the MHA's criteria, so a finding either way doesn't settle whether someone can be detained.
Fluctuating capacity, and saying one thing while doing another
- A one-off decision. If it can wait, see them at a better time, then record their decision and why you think they could make it. If it can't wait, do only what's needed to hold the position.
- Repeated decisions, like managing diabetes or money. Take a longer view of the material time. If they can decide only for short spells, it'll usually be right to treat them as lacking capacity.
- Talking the talk. After a brain injury especially, people can interview well yet be unable to act on what they say. Gather real-world evidence, put it to them, and expect more than one assessment.
- Won't engage. Unwilling isn't unable. Explain why it matters, but never threaten or force an assessment (Code 4.57). If they lack capacity to agree and don't object, it can usually go ahead (Code 4.58).
Who should assess capacity?
Usually whoever needs the decision made: the carer for day-to-day care, the clinician proposing treatment, the solicitor for a will (Code 4.38-4.41).
For complex decisions, get expert help from a psychiatrist, psychologist, speech and language therapist, occupational therapist or social worker. The final call stays with the decision-maker (Code 4.42). A surgeon can ask liaison psychiatry for advice but can't hand over the decision.
Get a second view when the decision is serious, the person disputes your finding, people disagree, there's a conflict of interest, or they tell different people different things (Code 4.53).
Recording a capacity assessment: what a good note shows
- The decision and the options, defined precisely.
- Why you doubted their capacity, even if you conclude they have it.
- The information and help you gave, and how you gave it.
- Their answers, verbatim where you can, so a reader can judge the conversation.
- Which ability failed, and how the impairment causes that.
- Why it's incapacity, not just an unwise decision.
The rules in brief
- Decision-specific. Capacity is about one decision now. A diagnosis, an IQ or a cognitive score doesn't decide it.
- Can they make the decision? Can they understand the relevant information, retain it long enough, use or weigh it, and communicate a decision by any means? Failing any one is enough.
- Then ask why. Is the inability because of an impairment of, or disturbance in, the functioning of the mind or brain? The Supreme Court in JB put this order beyond doubt.
- Standard of proof. The balance of probabilities.
- Over 16. The test applies from age 16.
Read more: MCA 2005, s2 · MCA 2005, s3 · MCA Code of Practice 2007, chapter 4: Assessing capacity · 39 Essex guidance note - assessment and recording of capacity (May 2025) (commentary)
Relevant information
You can only test someone on the information that actually matters to this decision.
What is relevant information?
It's what someone needs to know to make this decision: what the decision is, why it's needed, and the likely effects of each option, including deciding nothing (s3(4); Code 4.16). You give it to them. They don't have to work it out.
JB says you identify it within the specific facts of the case, and it can include consequences for other people (paras 69-73). It also has a ceiling: don't expect them to foresee more consequences than a person with capacity would (para 75).
Make the options real. Don't ask about 'home or a care home' in the abstract. Describe the actual care package and the actual home.
Relevant information for common decisions
| Decision | They need a broad grasp of | Usually not needed |
|---|---|---|
| Medical treatment | What it is, why it's proposed, the main benefits and risks for them, the alternatives, and what happens if they refuse | Every detail, or more than a patient with capacity would take in |
| Where to live | Each option and what it's like, the area, and living versus visiting. Activities, contact with family and friends, who they'd live with, the care on offer, and that rent and bills get paid | The cost of the placement, the legal nature of the tenancy, and very long-term effects on relationships |
| Care | What help they need and how often, who'd give it, what would happen without it, that carers don't always treat people well, and how to raise a concern | How the care is funded or managed |
| Contact with someone | Who it's with, the relationship, the kinds of contact possible, the good and bad sides, and any risk that person poses | Abstract ideas about friendship or family ties |
| Leaving hospital | That they're medically fit, that somewhere is available, perhaps with alternatives, and that the hospital will take steps if they won't go | Where they'll live long term, which is a separate decision |
These lists come from Court of Protection cases, gathered in a 39 Essex Chambers guidance note (April 2026). Start from them, then tailor them to the person in front of you.
Separate decisions, assessed separately
Residence and care are separate decisions, though you can look at them together when the facts tie them up. Leaving hospital is a different decision again. So is the capacity question for DoLS: whether they can consent to being accommodated there for care or treatment.
Consenting to a treatment and refusing it are one decision, not two. Someone can't have capacity to say yes but not to say no. The question is whether they can decide either way.
Serious decisions and the outcome trap
If a decision could have serious or grave consequences, it matters even more that they understand the information (Code 4.19). So check whether they can understand and weigh those consequences in particular.
That isn't judging the outcome. You're testing how they decide, not whether they reach your answer. A foolish decision made with capacity is still theirs to make.
A worked example
A 70-year-old man with vascular dementia is medically fit to leave a medical ward. He wants to go home. The team think a care home would be safer: he's fallen twice and forgets meals.
There are three decisions here: leaving hospital, where to live, and what care to accept. For residence, the options are home with the care package the council would actually provide, or a named care home. Show him what each would be like, and take him to see the home if that helps.
If he can weigh those concrete options and chooses home despite the risks, that's his choice. If he can't, because of his dementia, the decision moves to best interests.
The rules in brief
- Treatment. What it is, why it's proposed, the main benefits and risks for this person, the alternatives, and what happens if they say no.
- Where to live. What the options are and what each is like, the care that comes with each, and what each would mean for them day to day.
- Care. What help they need and with what, who would give it and how often, and what would happen without it.
- Leaving hospital. That they're medically fit to leave, and that there's somewhere they could go, perhaps with other options. And that if they won't go, the hospital can take steps to move them. Where they'll live and their care are separate decisions.
- Keep it reasonable. People need a broad grasp, not every detail. Nobody is asked to understand more than a capacitous person would.
Read more: MCA 2005, s3 · 39 Essex guidance note - relevant information for different categories of decision (Apr 2026) (commentary)
Questions trainees ask
What is a mental capacity assessment?
It's a check of whether someone can make a particular decision at the time it needs making. You test whether they can understand, retain, use or weigh the relevant information and communicate a decision. If they can't, you ask whether that's caused by an impairment of the mind or brain.
What is the two-stage capacity test?
First, can the person make the decision: understand, retain, use or weigh, and communicate? Then, if not, is that because of an impairment of, or a disturbance in the functioning of, the mind or brain? The Supreme Court in JB confirmed that order.
How many principles are in the Mental Capacity Act?
Five, in section 1: presume capacity, help people to decide, don't treat an unwise decision as incapacity, act in their best interests, and consider the less restrictive option.
What triggers a mental capacity assessment?
A reason to doubt someone's capacity for a decision that needs making now: their behaviour or circumstances, someone else's concern, or a known condition affecting the mind or brain. An unwise decision doesn't prove incapacity, but a pattern of them, or one that's obviously irrational or out of character, can be a reason to assess.
Who should assess capacity?
Usually the person directly concerned with the decision when it needs making, such as the clinician proposing the treatment. For complex decisions, ask someone with the right expertise.
What age does the Mental Capacity Act apply from?
Mostly from 16. Lasting powers of attorney, advance decisions to refuse treatment, statutory wills and need the person to be 18.
Is there a standard mental capacity assessment form?
The Act doesn't prescribe one. Whatever template you use should record the decision, the relevant information, the help you gave, what the person said, and how any inability is caused by an impairment.
What standard of proof applies to a capacity assessment?
The balance of probabilities. You need to show it's more likely than not that the person lacks capacity for this decision (s2(4)).
Test yourself
A 78-year-old woman with moderate dementia refuses a hip operation. She can explain the operation, its main risk and what will probably happen if she refuses. She'd rather live with the pain than risk the anaesthetic.
Show the answer
B. Capacity is about this decision, now. A diagnosis or a cognitive score doesn't decide it. She understands, retains, weighs and communicates, so her refusal stands even if you think it unwise.
Quick-fire
Capacity to make a decision is decided on
Show the answer
The balance of probabilities
Most of the MCA applies from age
Show the answer
16