Who Can Complete a Mental Capacity Assessment?

When someone may be struggling to make an important decision, one of the first questions families and professionals often ask is:

Who is allowed to complete a mental capacity assessment?

There is a common misconception that mental capacity assessments must always be completed by a doctor. In reality, this is not always the case. The right assessor depends on the decision being assessed, the reason the assessment is needed, and the type of evidence required.

Mental capacity is not assessed in a general way. A person is not simply found to “have capacity” or “lack capacity” for everything. Capacity is decision-specific and time-specific. This means the assessment must focus on the actual decision that needs to be made, at the time it needs to be made.

For more formal or complex decisions, it is important that the assessment is completed by someone with the right knowledge, training and practical experience in applying the Mental Capacity Act 2005.

Does a mental capacity assessment have to be completed by a doctor?

No. A mental capacity assessment does not always have to be completed by a doctor, GP or psychiatrist.

Doctors can be important in some cases, especially where there are complex medical or psychiatric issues. Medical evidence may help explain a diagnosis, condition or impairment that could affect the person’s decision-making.

However, a mental capacity assessment is not simply a medical opinion

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The assessment is about whether the person can make a specific decision for themselves. That means looking at whether they can understand the relevant information, retain it long enough to make the decision, use or weigh it as part of the decision-making process, and communicate their decision.

Because of this, doctors are not always the best suited professionals for every capacity assessment. Some decisions are more closely linked to care, welfare, safeguarding, family relationships, finances, property, communication, or the person’s everyday circumstances. In those cases, a suitably qualified social worker or specialist mental capacity assessor may be better placed to complete the assessment.

The better question is not: “Is the assessor a doctor?”

The better question is:

Does this assessor have the right experience for this specific decision?

Mental capacity assessments should use the functional test first

A good mental capacity assessment should not start with a diagnosis and then work backwards.

The correct approach under the Mental Capacity Act is to look first at the person’s ability to make the specific decision. This is often described as the functional part of the test.

The assessor should consider whether the person can:

• understand the information relevant to the decision

• retain that information long enough to make the decision

• use or weigh that information as part of the decision-making process

• communicate their decision by talking, signing, using gestures, assistive technology or any other means

Only if the person cannot do one or more of these things does the assessor then consider whether that inability is because of an impairment of, or disturbance in the functioning of, the mind or brain.

This distinction matters.

Someone may have dementia, a brain injury, a learning disability, a mental health diagnosis or another condition and still be able to make a particular decision. A diagnosis alone does not prove that a person lacks capacity.

Equally, someone may be unable to make one decision but able to make another. For example, they may be able to decide what they want to eat, but not be able to make a complex decision about selling a property or managing a large sum of money.

This is why capacity assessments must be decision-specific, evidence-based and clearly reasoned.

Can a social worker complete a mental capacity assessment?

Yes. A social worker can complete a mental capacity assessment where they have the right training, knowledge and experience for the decision being assessed.

Social workers often complete mental capacity assessments in relation to care, residence, safeguarding, contact with others, family circumstances, property and financial affairs, Court of Protection matters and deputyship applications.

A social worker may be particularly well suited to capacity assessments because they usually look at the person in the context of their real life. They consider the person’s support network, risks, communication needs, wishes, relationships, environment and practical circumstances.

This can be especially important where the decision is not purely medical.

For example, a decision about where someone should live is not just about diagnosis. It may involve understanding the person’s care needs, safety, relationships, routines, housing options, risks and what support could help them make the decision.

Similarly, a decision about managing finances may involve understanding the person’s actual money arrangements, bills, risks, debts, family pressures, vulnerability and ability to weigh consequences.

Why experience in mental capacity assessments matters

The quality of a mental capacity assessment depends heavily on the assessor’s experience.

Professional title alone is not enough. An assessor needs to understand how to apply the Mental Capacity Act test properly, how to identify the specific decision, how to decide what information is relevant, and how to support the person to take part in the assessment.

At Nellie Supports, completing mental capacity assessments is one of our team’s main roles. Our assessors regularly complete assessments across a wide range of decisions, including care, residence, finances, property, lasting power of attorney, COP3 forms, deputyship, litigation capacity and Court of Protection matters.

That level of practical experience is important because capacity assessments are often nuanced. The assessor must avoid common mistakes such as relying only on diagnosis, assuming a person lacks capacity because they make an unwise decision, or writing a conclusion without explaining the reasoning.

In some cases, a GP or doctor may know the person’s medical background well, but may not have the time, format or specialist capacity-assessment experience needed to produce a detailed decision-specific report. Medical evidence may still be useful, but it is not always the same as a full mental capacity assessment.

Who can complete a COP3 form?

A COP3 form is used in Court of Protection proceedings. It provides evidence about whether a person has capacity to make the decision or decisions in the application.

A COP3 form does not have to be completed only by a doctor. The current COP3 form refers to an “appropriate assessor” and gives examples including medical practitioners and social care professionals.

This is an important change in emphasis. It recognises that the right professional will depend on the decision being assessed and the expertise needed.

For example, some COP3 assessments may involve property and financial affairs. Others may involve welfare, care, contact, residence, litigation or another Court of Protection issue. In some cases, a medical professional may be appropriate. In others, a social worker or specialist mental capacity assessor may be better suited.

The assessor completing the COP3 should be able to explain their qualifications, training and practical experience. They should also be able to show that they understand the Mental Capacity Act 2005 and can apply the test properly.

Why the assessor’s reasoning matters

A mental capacity assessment should not simply state the final answer.

A good report should explain how the assessor reached their conclusion. This is especially important where the assessment may be relied on by a solicitor, the Court of Protection, a financial institution, a public body, or family members who disagree.

A clear assessment should explain:

• what decision was being assessed

• what information was relevant to that decision

• what support was given to help the person decide

• what the person said or demonstrated during the assessment

• whether the person could understand, retain, use or weigh the relevant information

• whether the person could communicate their decision

• whether any inability to decide was because of an impairment or disturbance in the functioning of the mind or brain

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Without this reasoning, a report may be too weak, too general or too unclear for the situation it is being used for.

Common mistakes about who can assess capacity

There are several common misunderstandings about mental capacity assessments.

One is the belief that only a doctor can assess capacity. This is not correct in many situations.

Another is the belief that a diagnosis automatically means the person lacks capacity. It does not. Capacity must be assessed in relation to the specific decision.

A third mistake is assuming that an unwise decision means the person lacks capacity. People are allowed to make decisions that others disagree with. The key question is whether they can make the decision for themselves, not whether others think the decision is sensible.

A further mistake is using someone who does not have enough experience in the type of decision being assessed. For complex, disputed or formal matters, the assessor’s experience can make a significant difference to the quality of the assessment.

When might you need a specialist capacity assessor?

A specialist capacity assessor may be needed where the decision is complex, disputed, high-value, urgent or likely to be scrutinised.

This may include situations involving:

• Court of Protection applications

• COP3 forms

• deputyship

• property sale or transfer

• financial decisions

• lasting power of attorney

• wills or estate planning

• litigation capacity

• care or residence disputes

• safeguarding concerns

• family disagreement

• concerns about undue influence

In these cases, the assessment often needs to do more than record a brief opinion. It needs to be structured, decision-specific and capable of being understood by others.

So, who is the best person to complete a mental capacity assessment?

The best person to complete a mental capacity assessment is the professional with the right expertise for the decision being assessed.

Sometimes that will be a doctor. Sometimes it will be a social worker. Sometimes it will be another professional with specialist knowledge of the person’s communication, care, circumstances, risks or decision-making needs.

For formal assessments, the assessor should understand the Mental Capacity Act 2005, be able to apply the functional test properly, and be able to explain their reasoning clearly.

The key point is this:

Mental capacity assessment is not about job title alone. It is about decision-specific expertise, proper application of the MCA test, and clear evidence-based reasoning.

Need support with a mental capacity assessment?

Nellie Supports provides independent, decision-specific mental capacity assessments for families, solicitors, deputies, attorneys and professionals.

Our team regularly completes mental capacity assessments as a core part of our work. This gives us extensive practical experience in applying the Mental Capacity Act test across a wide range of decisions and preparing clear, structured reports for legal, financial, care and Court of Protection purposes.

You can learn more about our mental capacity assessment services, or visit our COP3 mental capacity assessment page if the assessment is needed for the Court of Protection.