Author and Publication
Author: Nellie Supports Ltd
Publication Date: 15/05/2026
Citation
Mental Capacity Act 2005, c. 9. Available at: https://www.legislation.gov.uk/ukpga/2005/9/contents
Copywright
Copyright © 2026 Nellie Supports Ltd. All rights reserved.
This article is made available for general information, education and professional reference. It may be downloaded, printed and shared for non-commercial purposes, provided that it is reproduced in full, is not altered in any way, and is properly cited as the work of Nellie Supports Ltd. This material must not be edited, adapted, sold, republished, incorporated into commercial products, or used for commercial training, assessment, report-writing or advisory services without prior written permission from Nellie Supports Ltd.
This article does not constitute legal advice, clinical advice or a substitute for a decision-specific professional assessment. Where legislation, government guidance, court forms or external professional materials are referred to, those materials remain subject to their own copyright, licensing and re-use terms.
What is testamentary capacity?
Testamentary capacity is the mental capacity a person needs to make or change a valid will. The test comes from Banks v Goodfellow (1870): the person must understand the nature of making a will and its effects, understand in broad terms the extent of their estate, and appreciate the claims of those who might expect to benefit, with no disorder of the mind distorting their judgement in disposing of it. It is decision-specific: someone may lack capacity for complex financial management and still validly make a will. This guide explains the test, when to assess it and how a formal assessment protects a will from later challenge.
What testamentary capacity means
Testamentary capacity is the legal ability to make a valid will. A person has it if they understand what making a will involves and its effect, have a broad understanding of what they own, can appreciate the claims of those who might expect to benefit, and are not affected by a disorder of the mind that distorts their decision. It is judged at the time the will is made.
The legal test that applies
The standard comes from Banks v Goodfellow (1870), which remains the governing test in England and Wales. It is a common law test and is not the same as the functional test in the Mental Capacity Act 2005. A will is valid or invalid by reference to the four Banks v Goodfellow requirements, not by a generic capacity assessment.
Capacity is specific to the will in question
Testamentary capacity is decision-specific and time-specific. A simple will leaving everything to one person requires less understanding than a complex will dividing a large estate with conditions and trusts. The level of understanding expected rises with the size and complexity of the estate and the choices being made.
How it differs from financial capacity
Testamentary capacity is often confused with capacity to manage property and affairs, but they are separate decisions with different tests. A person may lack the capacity to run their day to day finances yet still have capacity to make a straightforward will, and the reverse can also be true. Each must be assessed on its own terms.
When capacity is most likely to be questioned
Concerns commonly arise where the testator was elderly or unwell, where the will was changed late in life, where it benefits an unexpected person, or where someone close to the testator was involved in arranging it. Cognitive decline, delirium, depression and delusional beliefs can all affect the decision and should be examined rather than assumed.
The role of the assessor
A capacity assessor gathers the relevant evidence, considers each limb of the test against the facts, and forms a reasoned opinion. They should record what they observed directly, separate it from information supplied by others, and explain how any diagnosed condition does or does not affect the will. The opinion should be capable of withstanding challenge.
Why contemporaneous assessment matters
An assessment carried out at or close to the time the will is made is far more valuable than one reconstructed later. It captures the testator's actual understanding and reasoning while it can still be observed. Where a will is high-risk or likely to be contested, a contemporaneous assessment significantly reduces the chance of a successful challenge.
What a sound opinion includes
A sound opinion records the instruction, the date and the will concerned, the Banks v Goodfellow test, the evidence relied on, the findings, an analysis against each limb, and a clear conclusion with any limitations stated. Where the assessor relies on records rather than direct examination, this should be made explicit.
Key takeaway
Testamentary capacity is the ability to make the specific will in question, judged by the Banks v Goodfellow test at the time of making. It is separate from financial capacity, sensitive to complexity, and best evidenced contemporaneously. A diagnosis alone neither proves nor disproves it.
Frequently asked questions
Is testamentary capacity the same as mental capacity generally?
No. Testamentary capacity is a specific legal test from Banks v Goodfellow concerned only with making or changing a will. It is assessed separately from other capacities, so a person may lack capacity to litigate or to manage complex finances and still have testamentary capacity, or the reverse.
Who can assess testamentary capacity?
A suitably experienced professional: specialist social workers, psychologists, psychiatrists or doctors familiar with the Banks v Goodfellow test and structured capacity assessment. No statute reserves the role to medical practitioners, and courts weigh the quality of the decision-specific reasoning over the assessor's title.
Can a person with dementia make a valid will?
Often, yes. A dementia diagnosis does not itself remove testamentary capacity, particularly in earlier stages or with good timing and support. What matters is whether, at the time of execution, the person meets the Banks v Goodfellow test, which is exactly what a contemporaneous assessment evidences.
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.
Considering a testamentary capacity assessment?
Nellie Supports completes testamentary capacity assessments across England and Wales, prospective, contemporaneous and retrospective, through a permanent employed team with every report peer reviewed before delivery. Call 0333 987 5118 or visit the testamentary capacity assessment service page.