GUIDES
Mental Capacity Act assessments examine the ability to make the particular decision with support, then whether any inability is caused by an impairment or disturbance of mind or brain.
Author: Nellie Supports Ltd
Publication Date: 15/05/2026
39 Essex Chambers, Mental Capacity Guidance Note: Carrying out and recording capacity assessments.
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Mental Capacity Act assessments examine the ability to make the particular decision with support, then whether any inability is caused by an impairment or disturbance of mind or brain. The sections below explain the evidence, practical steps and limits of the assessment or process.
The two-stage test is how the Mental Capacity Act 2005 decides capacity. Stage one is the functional question: can the person understand, retain, use or weigh the information relevant to the decision, and communicate their choice? Stage two is the diagnostic and causal question: if they cannot, is that because of an impairment of, or a disturbance in the functioning of, the mind or brain? Both stages must be satisfied and connected: the inability must be because of the impairment. This guide explains each stage, the order modern practice applies them in and the errors that undo reports.
The Mental Capacity Act 2005 decides capacity through a two-stage test. In modern practice the assessment starts with the functional question: can the person understand, retain, use or weigh the information relevant to this decision, and communicate their choice? If they cannot, the second question follows: is that inability because of an impairment of, or a disturbance in the functioning of, the mind or brain? Both limbs must be satisfied and connected before anyone concludes that capacity is absent. Working functionally first keeps the diagnosis from leading the conclusion.
The functional stage asks whether the person can understand the information relevant to the decision, retain it long enough to decide, use or weigh it as part of the process of deciding, and communicate the decision by any means. A person is unable to make the decision if any one of these is missing. The information must be specific to the actual decision rather than capacity in general, and the assessor must first take all practicable steps to support the person to decide for themselves.
After examining the person’s ability to make the decision with practicable support, consider any impairment or disturbance of mind or brain and whether it causes the identified inability. Temporary and permanent conditions may be relevant. A formal diagnosis is not always necessary, but the nature and evidential basis of the impairment must be explained. This is a sequence for reasoning, not a prohibition on obtaining relevant clinical history or arranging urgent medical assessment earlier.
Following A Local Authority v JB [2021] UKSC 52, first consider whether the person is unable to make the specific decision, after taking all practicable steps to support them. If they are unable, establish whether that inability is caused by an impairment of, or disturbance in, the functioning of the mind or brain. A diagnosis alone does not establish incapacity: the assessment must explain how the identified impairment causes the difficulty in making this decision.
Understanding means grasping the salient features of the decision and its reasonably foreseeable consequences, not every detail. Retention need only last long enough to make the decision, and a person who can hold information briefly may still have capacity. Notes, reminders and other support can help with both, and should be offered before any conclusion is reached.
Using or weighing is often the decisive element. It asks whether the person can bring the relevant information to bear, balance the options and consequences, and reach a decision through a reasoning process. A person who can repeat information but cannot use it, for example because a delusion or compulsion overrides it, may be unable to make the decision.
A person can communicate by speech, writing, signs, assistive technology or other means. Use all practicable communication support before concluding that this ability is absent. Difficulty speaking, a physical impairment or an unfamiliar communication style is not itself inability to make the decision.
A defensible record states the decision, the relevant information, the support provided, what the person said and did, the impairment identified, the functional analysis element by element, the causal link, and the conclusion. It should distinguish direct observation from reported information and acknowledge any limitations in the evidence.
A Mental Capacity Act finding requires a specific inability to decide despite practicable support and a causal explanation linking that inability to an impairment or disturbance of mind or brain. Record both elements with the decision, date, relevant information and evidence. Do not use a diagnosis or an unpopular outcome as a shortcut.
Modern practice asks the functional question first: what exactly can the person not do in relation to this decision? Only then does the assessor ask whether an impairment causes that inability, which stops the diagnosis leading the conclusion.
Failing any one of understanding, retaining, using or weighing the information, or communicating a decision, is enough for the functional stage, but only where the inability is caused by an impairment. An inability caused by fear, pressure or missing information is not incapacity under the Act.
Relevant information is the specific information the person actually needs for this decision: its nature, the realistic options and the reasonably foreseeable consequences of deciding either way or not deciding at all. It changes decision by decision.Can capacity change over time?Yes. Capacity is time-specific and can fluctuate or return, which is why assessments are anchored to a date and why significant decisions sometimes need reassessment when circumstances change.
The related pages below explain connected decisions, evidence requirements and legal processes.
Before seeking a report, write down the exact decision, relevant date, reason for concern and intended use. Gather the documents that explain the real options and any communication needs. Check any required form or court direction, agree the scope and total fee, and clarify how missing evidence or further questions will be handled.
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