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Financing care
Learn about funding options for home care, home adaptations and care homes, together with Attendance Allowance, gifting assets and Power of Attorney.
Housing options
Consider your options and learn about sheltered housing, retirement villages and care homes.
End of life
Guidance on the practical and emotional aspects at the end of life, from planning end of life care to arranging a funeral and coping with bereavement.

What is mental capacity?

Everyone should have the right to make choices about their own life. But sometimes injury, illness or disability can limit someone’s capacity to understand complex choices and make decisions. Someone’s mental capacity could be affected by:

  • a brain injury
  • dementia
  • a stroke
  • a severe learning disability.

Every situation is different. In some cases, a person’s mental capacity might only be affected temporarily. Or it may fluctuate over time, meaning that they’re able to make decisions one week but not the next. Or they might be able to make day-to-day decisions about shopping and meals, but be unable to make bigger decisions about financial affairs or care options.

Dementia and mental capacity

A person in the early stages of dementia might take longer to communicate, process information and understand choices. But this doesn’t necessarily mean that they have lost mental capacity and can’t make their own decisions.


If your loved one seems to be finding it difficult to understand or make choices, try thinking of different ways to help them. Are there other ways to explain the situation? Would it help to leave them with written information, rather than simply explaining verbally? Our guide on communicating with someone who has dementia offers useful advice.

Mental Capacity Act 2005 (England and Wales)

If the person you’re supporting is finding it increasingly difficult to make decisions, the Mental Capacity Act (MCA) can help. It supports people who want to plan for the future and ensures that their best interests are protected when they lack the mental capacity to make decisions about their care and treatment.


The MCA is aimed at empowering individuals to make their own decisions for as long as possible. It applies to individuals aged 16 and over living in England and Wales. Scotland has its own legislation that covers mental capacity and Northern Ireland has the Mental Capacity Bill, which are explained in more detail at the bottom of this article.


The MCA covers:

  • How to plan for the future
  • How mental capacity is assessed
  • Who can make decisions on someone else’s behalf and what rules they have to follow.

It says that:

  • It should always be assumed that someone has the capacity to make their own decisions, unless they’ve had a capacity assessment that proves otherwise
  • Individuals should be supported to make their own decisions wherever possible
  • Any decisions made on behalf of someone else must be in their best interests.

Advance care planning

Thinking about the future can be difficult, but if your loved one has an illness (such as dementia) where their ability to make decisions is likely to get worse, planning ahead can help them feel reassured that their wishes will be known and acted on by the people caring for them. 


The MCA allows people to set down their wishes for the future in case there comes a time when they are no longer able to make decisions for themselves. Under the MCA people can:

  • Appoint a trusted person (Power of Attorney in England and Wales, Scotland or Northern Ireland) to make decisions on their behalf should they lack capacity in the future.
  • Write an advance statement expressing their preferences for care and treatment. These are not legally binding but should be taken into account by those considering the person’s best interests.
  • Make an advance decision (also known as a ‘living will’) about certain medical or healthcare treatment that they don't want to receive if they ever lack the capacity to make their own decisions in future. For example, they might not want to receive life-saving treatment in the event of certain illnesses. Advance decisions are legally binding, as long as they meet specific criteria. 
Which? Wills
An advance decision (or living will) gives you control over your future medical decisions. Find out how Which? can help you set one up.

Who decides if someone has mental capacity?

Under the MCA, a person has the right to make their own decisions until they have been assessed (usually by a health professional) as lacking in mental capacity specific to the decision to be made at that time. The assessor will have to consider if the person can:

  • understand information related to the decision
  • remember information for long enough to make the decision
  • weigh up or use the information to reach the decision
  • communicate their decision to others, for example by talking, using sign language or hand signals or squeezing someone’s hand.

Remember, even if someone is assessed as lacking in mental capacity:

  • this will only apply to that decision at the time of the assessment
  • it’s not always permanent and they might be able to make their own decisions at a later time.
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Who can make decisions for someone that lacks mental capacity?

If your family member is assessed by a health professional as lacking mental capacity to make a decision, someone else will need to make that decision on their behalf. There are two main options.


A Lasting Power of Attorney: if your loved one appointed a Power of Attorney, this will now come into force. Remember that a Power of Attorney can only be made while someone still has the mental capacity to appoint one. For more information about the different types, costs and how to apply, see our Power of Attorney guide (in England and Wales, Scotland or Northern Ireland).


Deputy: if your family member didn't appoint a Power of Attorney, then the Court of Protection (the court responsible for decisions on financial or welfare matters for people who lack mental capacity and so can’t make decisions at the time they need to be made) will appoint a deputy to make decisions on their behalf. The Court decides who the deputy will be – it might be a trusted relative or friend, or a professional with the relevant skills. You can apply to become a deputy on the gov.uk website. The Court can also decide the length of the appointment and what types of decisions the deputy can or can’t make.


A deputy appointed to make healthcare or personal care decisions on a person’s behalf can decide things such as where they live, the type of care they receive and whether or not they should have medical treatment that doctors consider is in their best interests.


A deputy can’t make a decision that:

  • the person has the capacity to make for themselves
  • goes against a decision made by an attorney acting under a Lasting Power of Attorney
  • they have not been authorised to make by the Court of Protection
  • refuses treatment that would help the person stay alive for longer, should they develop a life-threatening medical condition
  • the person has already covered in an Advance Decision.

The Office of the Public Guardian supervises deputies in England and Wales. You can complain to them if you think that a deputy isn’t acting in your loved one’s best interests.

Adults with Incapacity (Scotland) Act

The Adults with Incapacity Act protects adults (aged 16 years and over) living in Scotland who lack mental capacity to make some or all of their own decisions. It allows people to make plans for their future and sets rules for who can take decisions on behalf of a person who is lacking mental capacity. 

The Mental Capacity Act (Northern Ireland)

In 2016, Northern Ireland introduced the Mental Capacity Act, bringing legislation in line with the rest of the UK. The Act outlines the High Court’s role in making decisions on someone’s behalf and the safeguards that have been introduced to protect the care, treatment and personal welfare of individuals with limited capacity.

Further reading

Living well with dementia

Dementia is life changing, but it shouldn’t stop you from living an independent life for as long as possible.

Power of Attorney

What is a Power of Attorney and why should you set one up? We also explain about Lasting Power of Attorney.

Last updated: 03 Sep 2019