Author and Publication
Author: Nellie Supports Ltd
Publication Date: 15/05/2026
Citation
39 Essex Chambers, Mental Capacity Guidance Note: Carrying out and recording capacity assessments.
Copywright
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Abstract
This guide explains how fluctuating capacity is handled under the Mental Capacity Act 2005 in England and Wales. It covers the time-specific nature of the two-stage test, conditions that cause capacity to vary, timing and supporting an assessment fairly, longitudinal evidence, one-off versus ongoing decisions and how fluctuation should be recorded in a defensible report.
Fluctuating capacity and mental capacity assessments
Some conditions do not remove capacity outright but cause it to come and go. Delirium, certain mental illnesses, dementia with sundowning, substance use and some neurological conditions can all produce fluctuating capacity, where a person can make a decision at one point in the day or week and not at another. The Mental Capacity Act 2005 handles this through its insistence that capacity is decision-specific and time-specific. This guide explains how assessors approach fluctuating capacity, how to time an assessment fairly, what evidence matters and how fluctuation should be recorded in a report.
What fluctuating capacity means
Fluctuating capacity describes a situation where a person's ability to make a particular decision varies over hours, days or weeks. The variation may follow a medical pattern, such as delirium resolving with treatment, lucid intervals in dementia, the cycle of a mental illness or the effects of medication, pain, fatigue or substance use. The law does not treat fluctuation as a special category of incapacity. Capacity is assessed for a specific decision at a specific time, so the question is always whether the person can decide the matter in front of them when the decision needs to be made.
The legal starting point: decision-specific and time-specific
Section 2(1) of the Mental Capacity Act 2005 asks whether a person is unable to make a decision at the material time because of an impairment of, or a disturbance in the functioning of, the mind or brain. Two consequences follow. First, a person who lacks capacity for a decision today may have capacity for the same decision next week, and neither finding contradicts the other. Second, the presumption of capacity in section 1 applies afresh at each new material time. A historical finding of incapacity is never a standing answer, and assessors must guard against letting an old assessment decide a new question.
Conditions where capacity commonly fluctuates
Fluctuation is most often seen in delirium, which can change over hours; in dementia, where alertness and processing can vary across the day; in psychotic and mood disorders, where insight can shift with the illness cycle; in epilepsy and other neurological conditions; and where alcohol, drugs, infection, pain or medication side effects temporarily disturb the functioning of the mind or brain. In each case the impairment limb of the two-stage test may be satisfied intermittently, which is why the timing of the functional questions matters so much.
Timing the assessment fairly
The Code of Practice expects decisions to be delayed where capacity is likely to be regained and the decision can wait. Where a decision cannot wait, the assessment addresses capacity at the time the decision must be made. In practice a fair assessment of fluctuating capacity often means choosing the time of day the person is at their best, avoiding periods of acute illness, checking with carers or nursing staff about patterns, and being willing to return. An assessment conducted at a person's worst moment, when a better moment was reasonably available, invites challenge.
Practicable steps when capacity varies
Section 1(3) requires all practicable steps to help the person decide before anyone concludes they cannot. With fluctuating presentations this includes assessing during lucid or settled periods, treating reversible causes first where possible, breaking information into stages, using written or visual aids the person can revisit, involving trusted supporters and repeating key information across sessions. The steps taken, and why they were chosen, should be visible in the report.
Longitudinal evidence and third-party accounts
A single interview is a snapshot, and with fluctuating capacity a snapshot can mislead in either direction. Strong assessments draw on longitudinal evidence: GP and hospital records, care home daily notes, medication changes, family and carer descriptions of good and bad periods, and where appropriate more than one assessment session at different times. The report should say what the pattern of fluctuation looks like, over what cycle, and how the evidence supports that description.
Fluctuating capacity in specific decisions
How fluctuation matters depends on the decision. A one-off decision, such as making a will or a lifetime gift, can often be timed for a settled period, and the report should evidence capacity at the moment of execution. Ongoing matters, such as managing finances or conducting litigation, are harder, because the person must be able to deal with a connected series of decisions over time. For ongoing decisions an assessor must consider whether the person can manage the matter across the realistic cycle of their condition, not only in a good spell.
Recording fluctuation in a capacity report
A court-ready report on fluctuating capacity states the material time it addresses, describes the pattern and likely causes of fluctuation, records when and how often the person was seen, sets out the practicable steps taken, and explains the functional findings and their causal link to the impairment at that time. It should also say whether reassessment is recommended and what trigger should prompt it. Vague conclusions that capacity fluctuates, with no time anchor, are of little use to families, solicitors or the Court of Protection.
Key takeaway
Fluctuating capacity does not weaken the Mental Capacity Act framework; it makes disciplined use of it more important. Capacity is always assessed for a specific decision at a specific time, with the person supported to decide at their best realistic moment. Where a decision can wait for capacity to return, it usually should. Where it cannot, a properly timed, properly evidenced and properly recorded assessment protects the person and the decision alike.
Frequently asked questions
Can someone have capacity in the morning but not the afternoon?
Should a decision be delayed until capacity returns?
How many sessions does a fluctuating capacity assessment need?
Related mental capacity assessment pages
These internal links help readers move from this guide to the most relevant Nellie Supports service page, assessment option or legal framework page.
Need an assessment where capacity fluctuates?
Nellie Supports provides independent, decision-specific mental capacity assessments across England and Wales through a permanent employed team of registered professionals, with a same working day response to every enquiry and every report peer reviewed before delivery. Call 0333 987 5118 or visit the mental capacity assessment service page.