Factsheet: A brief guide to the Mental Capacity Act 2005

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Summary

June 2025 (FS18)

This factsheet explains the Mental Capacity Act.

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What is mental capacity?

Having mental capacity means being able to make your own decisions. Someone who is lacking mental capacity may not be able to make a decision at the time the decision needs to be made.

Do not make assumptions about someone’s mental capacity based on their age, appearance, behaviour or health condition.

What is the Mental Capacity Act?

The Mental Capacity Act is the main law in England and Wales that protects adults who lack capacity to make some or all of their own decisions, and it determines how those decisions can be made.

All adults have the right to make their own decisions about their life, including decisions about their care and support. They should be helped and supported to do this if they can’t do it on their own.

The Mental Capacity Act 2005 has a capacity test and a Code of Practice for anyone caring for someone over 16 years old. This includes doctors, social workers, paid carers and other health and social care professionals. It tells them what to do when they are working with someone who lacks capacity.

Simple decisions like what to eat, and more complicated decisions like where to live and what medical treatment to have are all included.

Some decisions like marriage, civil partnership, consenting to sexual relationships, adoption and voting are not covered by the Mental Capacity Act. Nobody can make these decisions for someone else.

The principles of the Mental Capacity Act

There are five key principles that underpin the Act:

Assume people have capacity.
Support people to make decisions for themselves.
People who make unwise decisions may still have capacity.
Actions must be in the best interests of the person who lacks capacity.
Less restrictive options must be considered first.

How is mental capacity assessed?

If a social or health care professional thinks that someone lacks mental capacity, they must do a mental capacity assessment before they ask them to consent to any care or treatment.

They must do the assessment at the time the decision needs to be made, because people’s capacity to make decisions can change, and people may have capacity to make one decision but not another.

3-stage capacity test

The 3-stage capacity test will answer the following questions:

1. Is the person able to make the decision, at the time that the decision needs to be made? Can they:

understand information about the decision that needs to be made?
remember the information long enough to make the decision?
weigh up the information to make the decision?
communicate their decision?

2. Does the person have an impairment or disturbance that affects the functioning of their mind or brain?

3. Is the person unable to make the decision because of this impairment or disturbance?

Who decides if a person lacks capacity?

A family member, health, social care or other professional might need to decide if someone is unable to make a particular decision. They will do this using the 3-stage capacity test above.

If the person needs to consent to treatment or medical examination, the doctor or healthcare professional will decide whether they have capacity.

What happens when a person cannot make their own decisions?

People should be supported to make their own decisions.

If someone cannot make a particular decision and they do not have a legal representative then someone else, like a carer or professional, will have to make a ‘best interests decision’.

How does someone work out what is in a person’s best interests?

Best interests means what is best for a person, once all things have been considered.

The Act has a ‘best interest checklist’ and it can be useful for people involved in someone’s care to meet as a group to discuss what is in their best interests.

Best interests checklist

Working out what is in someone’s best interest cannot be based on age, appearance, condition or behaviour.
All relevant circumstances should be considered when working out someone’s best interests.
Every effort should be made to encourage and enable the person who lacks capacity to take part in making the decision.
If there is a chance that the person will regain the capacity to make a particular decision, then you should consider delaying the decision unless it’s urgent.
The person’s past and present wishes and feelings, beliefs and values should be taken into account.
The views of other people who are close to the person should be considered, as well as the views of an attorney or deputy.

Protecting a person from ill-treatment or wilful neglect

There are two criminal offences under the Act:

ill treatment of a person without capacity
willful neglect of a person without capacity

These offences carry a sentence of up to 5 years imprisonment and/or a fine.

Planning ahead

A ‘next-of-kin’ has no legal status when someone is alive. They cannot consent on someone’s behalf or access their medical history. They have no claim on someone’s finances or personal possessions. They cannot take over someone’s banking and bills.

A Lasting Power of Attorney (LPA) should take care of these things. A Lasting Power of Attorney allows a person to appoint someone to make decisions for them in the future if they lose the capacity to do this for themselves. This could be decisions about property and finance or health and welfare, or both. There is more information about this in our factsheet: Managing someone’s affairs.

A ‘next-of-kin’ is legally valid if someone dies without leaving a will. Their estate will be passed on to the the closest blood relatives.

Advance decisions to refuse treatment

Someone can make an advance decision or ‘living will’ about treatment that they do not want to receive in the future if they lose mental capacity.

Advance decisions are legally binding and must be followed by doctors and other health staff (as long as the person is 18 or over and has the mental capacity to make the decision to begin with).

The decision should say which treatment/s are being refused and in what circumstances.

An advance decision does not need to be in writing but is helpful if it is.

Making advance decisions about life-sustaining treatment

‘Life-sustaining treatment’ is treatment that is needed to keep someone alive. There are some specific rules if someone wants to make an advance decision to refuse life-sustaining treatment.

This decision must:

be in writing
state that it applies even if the person’s life is at risk
be signed by the person (or by someone else that has been appointed by the person, in front of the person)
be signed in front of a witness
be signed by the witness in front of the person

Recording the person’s wishes and feelings about the treatment and care

A person can write down or tell people their wishes and preferences about future treatment or care.

Court of Protection

The Court of Protection (the Court) protects the rights of people who do not have mental capacity. It makes decisions on:

capacity
property and finance
health and welfare
disagreements about best interests

What is a deputy?

The Court can appoint a deputy to make ongoing decisions for someone who lacks capacity. A deputy must be 18 years or over and can be a relative, friend or professional.

They can deal with financial affairs and/or personal and welfare issues.

Independent Mental Capacity Advocates (IMCA)

An IMCA helps people who lack capacity to make important decisions when they have no family, friends or a legal representative to do this. IMCAs are specially trained to support people who lack capacity. They must be involved if the decision is about serious medical treatment or a change of accommodation (more than 28 days in hospital or 8 weeks in a care home).

An IMCA may also be involved in some accommodation reviews, safeguarding adult enquiries and deprivation of liberty safeguards.

For more information, read our factsheet: Independent advocacy.

Challenging decisions and raising concerns

Sometimes there may be disagreements about decisions made under the Act, such as the assessment of capacity to make a decision. There are a number of ways that disagreements can be sorted out:

Informal meetings (may include advocacy services).
Using an organisation’s complaints procedure, such as the NHS or local authority.
Speaking to the Office of the Public Guardian if there are concerns about the way a Lasting Power of Attorney is being used.

The Court has the final say about disagreements.