Principle four, of the five principles specified in the Mental Capacity Act 2005, states:
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.
The principle covers all aspects of financial, personal welfare and healthcare decision-making and actions. It applies to anyone making decisions or acting under the provisions of the Mental Capacity Act 2005. This includes family carers, care workers, health and social care staff, attorneys appointed under a Lasting Power of Attorney or Enduring Power of Attorney, and deputies appointed by the Court of Protection.
Section 4 of the Act sets out how to determine the Best Interests of a person who lacks Capacity, to make a decision at the time it needs to be made.