LPA and the Mental Capacity Act UK (2026): Capacity, Best Interests and Attorney Powers
Updated 13 May 2026 · 9 min read · England & Wales
A Lasting Power of Attorney does not exist in a legal vacuum. It operates within the framework of the Mental Capacity Act 2005 — the statute that defines when an attorney can act, how they must make decisions, and what happens when they do not. Every person who holds an LPA, or is considering making one, should understand the basics of the Act.
What the Mental Capacity Act 2005 does
The MCA 2005 provides the legal framework for all decisions made on behalf of people who lack mental capacity in England and Wales. It sets out:
- Who has (and who lacks) capacity, and how to assess it
- The five principles all decision-makers must follow
- How “best interests” decisions must be made
- The powers and limits of LPA attorneys
- The role of the Court of Protection and the Office of the Public Guardian
- Criminal offences for ill-treatment or neglect
Every registered LPA is subject to the MCA 2005. Attorneys who act outside its framework are acting unlawfully — regardless of what the LPA document itself says.
The five principles of the Mental Capacity Act
Section 1 of the MCA 2005 sets out five overriding principles. Every decision made under a registered LPA must be consistent with all five:
| Principle | What it means in practice |
|---|---|
| 1. Presumption of capacity | Assume the donor has capacity unless you have assessed otherwise |
| 2. Right to be supported | Take all practicable steps to help the donor decide for themselves |
| 3. Unwise decisions | Capacity cannot be denied just because the donor makes a decision you consider unwise |
| 4. Best interests | Every act or decision for a person lacking capacity must be in their best interests |
| 5. Least restrictive option | Choose the option that least restricts the donor’s rights and freedoms |
The capacity test: decision-specific and time-specific
Capacity under the MCA 2005 is not a binary global state — it is assessed for each decision at the time that decision needs to be made. A person may have capacity to decide what to eat for breakfast but not to manage a complex investment portfolio.
A person lacks capacity for a specific decision if they cannot do all four of:
- Understand the information relevant to the decision
- Retain that information long enough to make the decision
- Use or weigh the information as part of the decision-making process
- Communicate their decision (by any means)
The inability must result from an impairment or disturbance in the functioning of the mind or brain. A diagnosis of dementia, stroke, or mental illness does not automatically mean capacity is absent — the test is functional, not diagnostic.
When can an LPA attorney act?
Property and Financial Affairs LPA: By default, the attorney can only act when the donor lacks capacity. The LPA can be drafted to allow the attorney to act while the donor still has capacity (useful for practical convenience) — but acting without the donor’s consent when they have capacity is unlawful.
Health and Welfare LPA: Can only ever be used when the donor lacks capacity to make the specific health or welfare decision at the time it arises. A health professional should document the capacity assessment before acting on the attorney’s instructions.
What “best interests” actually means
The best interests standard is not “what the attorney thinks is best”. Section 4 of the MCA 2005 requires the attorney to:
- Not make assumptions based on age, appearance, condition, or behaviour
- Consider whether the person might regain capacity and the decision can wait
- Involve the donor in the decision as far as possible
- Consult family, carers, and anyone named in the LPA
- Have regard to the donor’s past and present wishes, feelings, beliefs, and values
- Consider less restrictive alternatives
The test is intentionally holistic — it cannot be reduced to a simple checklist. In disputes, the Court of Protection applies this test when reviewing attorney decisions.
What attorneys cannot do under the MCA 2005
The MCA 2005 places hard limits on attorney authority that the LPA document itself cannot override:
- Cannot make or change a will — only the Court of Protection can authorise a statutory will for someone lacking capacity
- Cannot make large gifts — only gifts that are reasonable given the donor’s relationships and estate size, or the Court of Protection authorises
- Cannot override an advance decision to refuse treatment that pre-dates the LPA and applies to the specific situation
- Cannot use the donor’s funds for personal benefit beyond reasonable LPA-authorised expenses
- Cannot act if the LPA is revoked, or if the attorney loses capacity or (for spousal attorneys) the relationship is dissolved
The Office of the Public Guardian and attorney accountability
The Office of the Public Guardian (OPG) registers LPAs and investigates concerns about attorney conduct. Anyone can raise a safeguarding concern with the OPG online or by phone. The OPG can:
- Investigate the attorney’s actions and request accounts
- Apply to the Court of Protection to revoke the LPA and remove the attorney
Serious abuse — financial exploitation, physical or emotional neglect — can also result in criminal prosecution under s44 MCA 2005 (ill-treatment or wilful neglect), carrying up to 5 years’ imprisonment.
Frequently asked questions
What is the Mental Capacity Act 2005 and why does it matter for LPAs?
The Mental Capacity Act 2005 (MCA 2005) is the statutory framework that governs decision-making for people who lack capacity to make decisions for themselves in England and Wales. It is the legal foundation for Lasting Powers of Attorney — an LPA only becomes operable when the donor lacks capacity to make the relevant decision, and attorneys must act in accordance with the MCA's principles and best interests framework at all times. The MCA also created the Court of Protection (which can make deputyship orders when there is no LPA) and the Office of the Public Guardian (which registers LPAs and investigates attorney misconduct). Every attorney under a registered LPA is legally required to understand and apply the MCA 2005.
What is the Mental Capacity Act capacity test?
The MCA 2005 capacity test is decision-specific and time-specific (s2–3 MCA 2005). A person lacks capacity for a particular decision at a particular time if they are unable to: (1) understand the information relevant to the decision; (2) retain that information long enough to make the decision; (3) use or weigh that information as part of the decision-making process; or (4) communicate their decision (by any means). All four limbs must be satisfied for a person to have capacity. Capacity is assessed decision by decision — a person may lack capacity for complex financial decisions but retain capacity for simpler choices. The inability must arise from an impairment of, or disturbance in, the functioning of the mind or brain. A diagnosis alone (e.g. dementia) does not mean capacity is absent.
What are the five principles of the Mental Capacity Act 2005?
Section 1 MCA 2005 sets out five statutory principles that govern all decisions under the Act: (1) Presumption of capacity — a person must be assumed to have capacity unless it is established that they lack it. (2) Right to be supported — all practicable steps must be taken to help a person make their own decision before concluding they cannot. (3) Unwise decisions — a person is not to be treated as lacking capacity merely because they make an unwise decision. (4) Best interests — any act done or decision made for a person who lacks capacity must be in their best interests. (5) Least restrictive option — any act or decision must be the least restrictive of the person's rights and freedom of action. Attorneys under an LPA are legally bound by all five principles.
When can an LPA attorney start using their authority?
A Property and Financial Affairs LPA: if the LPA specifies it, the attorney can act while the donor still has capacity (with the donor's consent). Unless specified, the attorney can only act when the donor lacks capacity. A Health and Welfare LPA: can only be used when the donor lacks capacity to make the specific health or welfare decision at the relevant time. In practice for a Property and Financial Affairs LPA: the attorney should formally assess whether the donor has capacity for the specific financial decision before acting on their behalf. Acting under a registered LPA while the donor has capacity (and without their consent) is an unauthorised act and potentially a criminal offence under the MCA 2005.
What is a 'best interests' decision under the Mental Capacity Act?
When an attorney makes a decision on behalf of a donor who lacks capacity, they must act in the donor's best interests (s4 MCA 2005). This is not what the attorney thinks would be best — it requires: (1) not making assumptions based on age, appearance, condition, or behaviour; (2) considering whether capacity might be regained and whether the decision can wait; (3) involving the donor as far as possible; (4) consulting anyone named in the LPA as someone to be consulted, and other carers, family and friends; (5) considering the donor's past and present wishes, values, and beliefs; (6) considering less restrictive alternatives. The checklist is non-exhaustive — best interests is a holistic judgement, not a mechanical test. For life-sustaining treatment decisions under a Health and Welfare LPA, the attorney must not be motivated by a desire to bring about the donor's death.
What can an attorney NOT do under an LPA?
An attorney under a Property and Financial Affairs LPA cannot: make a gift beyond the scope of what is reasonable for the donor's relationships and estate (unless the court authorises it); use the donor's assets for the attorney's own benefit (unless the LPA expressly permits reasonable expenses); make or change a will (only the Court of Protection can authorise a statutory will for someone without capacity); change the terms of an LPA. An attorney under a Health and Welfare LPA cannot: consent to or refuse life-sustaining treatment unless the LPA expressly grants this power; override a valid advance decision to refuse treatment (living will) that pre-dates the LPA and covers the situation. All attorneys: cannot act once the LPA is revoked, once they lose capacity themselves, or (for married donors) once the donor-attorney marriage is dissolved.
What happens if an attorney abuses their LPA powers?
Attorney misconduct is investigated by the Office of the Public Guardian (OPG). Any person can report concerns. The OPG can investigate and, if abuse is found, apply to the Court of Protection to revoke the LPA and remove the attorney. In serious cases, the attorney can be prosecuted under the MCA 2005 for ill-treatment or wilful neglect of a person lacking capacity (s44 MCA 2005) — carrying up to 5 years imprisonment. Financially abusive attorneys can also face civil claims for breach of fiduciary duty and be required to repay misappropriated funds. Choosing a trustworthy attorney and naming a replacement or joint attorney provides protection.
Make your LPA with confidence
WillSafe’s LPA Guidance Pack walks you through both the Property and Financial Affairs LPA and the Health and Welfare LPA — including how to choose attorneys who will apply the Mental Capacity Act correctly.
Get the LPA Guidance Pack →Related guides
- What is a Lasting Power of Attorney?
- Property and Financial Affairs LPA — full guide
- Health and Welfare LPA — full guide
- Making an LPA after a dementia diagnosis
- Statutory wills — when the Court of Protection makes a will
- Enduring Power of Attorney — old EPAs and the transition to LPAs