Mental Capacity Act 2005

The Mental Capacity Act 2005 is a piece of legislation that supports the rights of people to be empowered to make decisions for themselves where they can.

The Act also provides a legal frame work for acting and making decisions on behalf of individuals who lack capacity to make a particular decision and applies to everyone involved in care and treatment of people age 16 and over.

The Act is underpinned by 5 Statutory Principles:

  1. a person must be assumed to have capacity unless it is established that they lack capacity
  2. a person is not to be treated as unable to make a decision unless all practicable steps to help him to do so have been taken without success
  3. a person is not to be treated as unable to make a decision merely because he makes an unwise decision
  4. an act done, or decision made, under this act for or on behalf of a person who lacks capacity must be done, or made, in his best interests
  5. before the act is done, or the decision is made, regard must be had to whether the purpose for which it is needed can be as effectively achieved in a way that is less restrictive of the person’s rights and freedom of action

If a person is assessed as lacking capacity, any actions or decisions made for or on their behalf must be in the persons best interest.

The person’s past and present wishes and feelings, beliefs and values should be taken into account and the views of other people who are close to the person who lacks capacity should be considered, as well as the views of an Attorney or Deputy.

If you lack the capacity to make decisions

If you lack capacity to make your own decisions or act for yourself, a professional may need to make decisions on your behalf. The Mental Capacity Act 2005 ( provides a legal framework to ensure that the person making decisions for you acts in your best interests and are not overly restrictive or controlling. The person making the decisions for you may be a:

  • family member
  • friend
  • carer

You can give this person lasting powers of attorney (this is a legal document which allows your chosen person(s) to act and make decisions on your behalf when you do not have the mental capacity to make decisions).

Not everyone has a network of people able to help them decide on important issues. If you lack capacity and have no family or friends to help, you can receive support from an Independent Mental Capacity Advocate. They will assess your situation and ensure that decisions are made in your best interests.

A doctor or other professional may become involved if the decision is more complex, for example if you need medical treatment for a serious condition and you have not made an advanced decision to refuse the treatment.

A Code of Practice (PDF, 1.4MB) accompanies the Act and all professionals including GPs, social workers and paid carers must have regard to the guidance while supporting people who lack the capacity to decide for themselves.

Where individuals are staying in hospitals or living in care homes, and may need to be deprived of their liberty in order to protect them from serious harm, Deprivation of Liberty Safeguards apply. These safeguards are in place to protect very vulnerable people from arbitrary decision making and ensure that they have a voice.

You can make an advance decision to refuse treatment if you are aged 18 years or above and have mental capacity. You can decide that you do not want a particular type of medical treatment if it was ever needed in the future and you lacked capacity at that time. Friends and family should be informed of your decision so that they can speak on your behalf.

Further information

The Department for Constitutional Affairs has produced the following guides:

Page last reviewed: 05 July 2022

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