Best Interests Decision
A best interests decision is a decision made on behalf of a person who lacks the mental capacity to make that decision themselves, as required by the Mental Capacity Act 2005. Decision-makers must consider the person's past and present wishes, feelings, values, and beliefs, and involve relevant people in their life. For serious decisions involving deprivation of liberty or significant medical treatment, an application to the Court of Protection may be required.
The Mental Capacity Act 2005 sets out a statutory checklist for best interests decisions (section 4). Decision-makers must not make assumptions based on age, appearance, condition, or behaviour; must consider whether the person may regain capacity; and must involve the person as far as possible. They must consult anyone named by the person, carers, family members, and any attorney or deputy. An Independent Mental Capacity Advocate (IMCA) must be instructed for serious medical decisions or changes of accommodation where there is no one else to consult. Decisions must be the least restrictive option. Deprivation of Liberty Safeguards (DoLS) — or the Court of Protection under the Liberty Protection Safeguards expected to replace DoLS — are required where a person in a care home or hospital is deprived of their liberty, even in their best interests.
In practice, a best interests decision is made by whoever is proposing to act — the surgeon proposing an operation, the social worker proposing a move, the attorney proposing to sell a house. There is rarely a meeting called "the best interests meeting" unless the decision is serious or contested. What the law requires is that the decision-maker can show they worked through the statutory checklist and recorded their reasoning, decision by decision. Capacity is time-specific and decision-specific: someone may lack capacity to decide where to live but retain capacity to decide what to eat, who to see, and whether to accept a flu jab.
Worked example: Joan has moderate dementia and is medically fit for discharge from hospital. The ward wants to discharge her to a care home; her son wants her home with a care package. The decision-maker must first assess whether Joan can make the decision herself with support — using her best time of day, plain language, and visual prompts. If she cannot, they must record her known wishes (she has always said she wants to die at home), consult her son and anyone named by her, weigh the risks of both options rather than only the risks of going home, and choose the least restrictive option that meets her needs. If the family and the trust cannot agree, the dispute goes to the Court of Protection rather than being settled by whoever shouts loudest.
Common misconceptions cause real harm. Best interests does not mean what the professionals think is safest — an unwise choice by someone with capacity must be respected, and even for someone without capacity, their past and present wishes carry substantial weight. Being next of kin gives no legal authority to consent on another adult's behalf; only a registered health and welfare attorney or a court-appointed deputy has that. And a valid advance decision refusing specific treatment is binding and overrides a best interests judgment entirely.
Best interests decisions flow from the Mental Capacity Act 2005, can be pre-empted by a lasting power of attorney, may trigger Deprivation of Liberty Safeguards, and often overlap with adult safeguarding. If a decision is being made about someone you care for, read our guide to best interests decisions and ask for the reasoning in writing.
Related guides
Best Interests Decisions
When someone lacks mental capacity to make a specific decision, others must make it for them in their best interests. The Mental Capacity Act 2005 sets out a detailed framework for how best-interests decisions must be made, placing the person at the centre and requiring decision-makers to consider their wishes, feelings, and values.
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Mental Capacity Act Basics
The Mental Capacity Act 2005 (MCA) is the law that governs decisions made for people who lack the mental capacity to make specific decisions themselves. It applies to all adults in England and Wales and underpins how healthcare, social care, and legal decisions are made for vulnerable people.
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Advance Decisions and Living Wills
An Advance Decision to Refuse Treatment (ADRT), sometimes called a living will or advance directive, is a legally binding document under the Mental Capacity Act 2005. It allows you to specify in advance which medical treatments you would refuse in specific circumstances, to take effect when you no longer have capacity to decide for yourself.
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