Wills Drafting and Testamentary Capacity: A Guide for Solicitors

Contentious probate claims are rising, and a disproportionate number turn on a single question: did the testator have the mental capacity to make the will? For solicitors who draft wills, understanding exactly what the law requires — and building a file that can withstand a challenge years after the client has died and can no longer explain themselves — is not optional practice management. It is the difference between a will that holds up and one that ends up in the High Court.

This guide sets out the current legal test for testamentary capacity, how it sits alongside the Mental Capacity Act 2005, the 'golden rule' for taking instructions from elderly or seriously ill clients, and the practical steps and drafting habits that reduce the risk of a will being challenged.

The test for testamentary capacity: Banks v Goodfellow

The starting point remains the common law test set out over 150 years ago in Banks v Goodfellow (1870) LR 5 QB 549, and it has never been displaced by statute. To have testamentary capacity, a testator must, at the time of giving instructions and executing the will:

• Understand the nature of the act of making a will and its effects;
• Understand the extent of the property of which they are disposing;
• Be able to comprehend and appreciate the claims to which they ought to give effect — in other words, understand who might expect to benefit and be able to weigh those claims; and
• Not be affected by any disorder of the mind that perverts their sense of right, or any insane delusion that influences the disposal of their property.

The test is decision-specific and time-specific: capacity is assessed by reference to the particular will being made, at the point it is made, not as a general or permanent state. A client who has good days and bad days may have capacity on the day they give instructions but not on the day they later attend to execute the will, or vice versa — which is precisely why contemporaneous evidence matters so much, as set out below.

Banks v Goodfellow and the Mental Capacity Act 2005: which test applies?

Solicitors are often understandably confused about how the four-limb Banks v Goodfellow test sits alongside the statutory capacity framework in the Mental Capacity Act 2005 (MCA 2005), which governs capacity for living decision-making generally, including decisions solicitors help clients make about property, finances and welfare during their lifetime.

The courts have now considered this question directly. In Walker v Badmin [2014] EWHC 1372 (Ch), Deputy High Court Judge Nicholas Strauss QC held that Banks v Goodfellow remains the correct test for testamentary capacity, and that the MCA 2005 does not displace it. He noted that the two tests will not always produce the same answer — the MCA presumes capacity unless it is shown to be lacking, whereas the common law test is satisfied once a 'real doubt' is raised, and the MCA requires understanding of the reasonably foreseeable consequences of a decision, which is a wider enquiry than the Banks v Goodfellow requirement to appreciate the claims a testator ought to consider. Because the MCA is aimed at protecting living people making ongoing decisions, and Parliament gave no indication it intended to alter the long-standing and lower threshold for testamentary capacity, the common law test prevails.

More recently, in Leonard v Leonard [2024] EWHC 321 (Ch), the High Court again confirmed that Banks v Goodfellow is the applicable test in contentious probate, reinforcing that practitioners should not treat an MCA-compliant capacity assessment carried out for lifetime purposes (for example, for a lasting power of attorney) as automatically sufficient evidence of testamentary capacity. The two assessments ask different questions, and a solicitor instructing a medical practitioner to assess a client should be clear that they need an opinion directed specifically at the Banks v Goodfellow criteria, not a general MCA capacity assessment.

The golden rule: protecting clients and your firm

Separately from the legal test itself, the profession has long followed a practical safeguard known as the 'golden rule', first articulated by Templeman J in Kenward v Adams (1975). The golden rule is not a rule of law — a will is not invalid simply because it was not followed — but it is close to standard professional practice, and its absence is frequently used against a solicitor in a later capacity dispute.

The golden rule provides that where a testator is elderly, seriously ill, or there is any other reason to doubt their capacity, the solicitor taking instructions should arrange for a medical practitioner to examine the testator, form a view on capacity by reference to the Banks v Goodfellow criteria, and make a contemporaneous written record of that assessment — ideally witnessing or approving the will itself. Best practice, reflected in Law Society guidance on working with clients who may lack capacity, is to instruct the GP or, where there is a specific concern such as dementia, a specialist, and to keep the medical practitioner's note on file indefinitely, not just until probate is granted.

The golden rule will not be appropriate or practical in every case, and following it is not a guarantee against a challenge. But a solicitor who can produce a contemporaneous medical capacity assessment, taken at the time instructions were given, is in a far stronger position than one relying on memory or a general impression formed years earlier.

Practical steps to reduce the risk of a will being challenged

Beyond the golden rule itself, several habits consistently reduce the risk of a successful capacity or undue influence challenge:

• Detailed attendance notes. Record who was present, how instructions were given, the client's demeanour, and — critically — the client's own reasoning for their testamentary decisions, in their own words where possible. A note that simply records the gifts made is far less useful than one that records why the client wanted to leave more to one child than another.
• See the client alone. Take instructions without family members, carers or proposed beneficiaries present, even if they arranged or attended the appointment. This is one of the clearest ways to guard against undue influence and to test the client's own understanding.
• Be alert to red flags for undue influence. A sudden, unexplained change from a long-standing testamentary pattern, a new or recently-introduced beneficiary driving the instructions, or a client who appears anxious to please a third party, all warrant closer scrutiny and fuller notes.
• Avoid drafting for family members without independent advice. Where a solicitor is asked to prepare a will for a relative, or where a beneficiary has been involved in introducing the client or arranging the appointment, consider whether independent advice is needed and document why the arrangement is appropriate if it proceeds.
• Capacity assessments should be specific. As Leonard v Leonard illustrates, ask the assessing practitioner to address the Banks v Goodfellow criteria directly, not simply confirm the client has capacity in general terms.
• Keep the file. Attendance notes, capacity assessments and drafts should be retained well beyond execution — often for the client's lifetime and beyond, given that challenges typically surface only after death, during the administration of the estate. For firms handling the subsequent administration, our guide to estate accounts and administration covers the practicalities that follow once a grant is obtained.

Common drafting pitfalls that lead to disputes

Capacity is not the only source of contentious probate work. Poor drafting generates a steady stream of disputes and rectification claims, and most fall into a small number of recurring categories:

Ambiguous gifts

Gifts described loosely — 'my jewellery', 'the contents of my house', references to property by an address that has since changed, or gifts to a class of beneficiaries ('my grandchildren') without clarifying whether step-grandchildren or those born after death are included — invite dispute. Precision in describing both the asset and the intended recipient matters more than concise drafting; clear, unambiguous language is not a stylistic preference but a risk-management tool.

Failure to account for lapse and ademption

A gift lapses if the beneficiary predeceases the testator (subject to the section 33 Wills Act 1837 substitution provisions for gifts to issue), and a specific gift adeems if the asset no longer forms part of the estate at death. Wills that fail to include contingency or substitutional gifts, or that fail to address what happens if a named beneficiary dies first or an asset is sold, routinely generate disputes about what the testator would have wanted — disputes that a well-drafted contingency clause would have avoided entirely.

Poorly drafted residuary clauses

The residuary clause is arguably the most important provision in the will, since it captures everything not otherwise disposed of, yet it is often drafted as an afterthought. A residuary gift that fails — because, for example, the sole residuary beneficiary predeceases the testator and no substitution is included — can result in a partial intestacy, undermining the testator's overall intentions and creating exactly the kind of dispute the will was meant to prevent.

Frequently asked questions

Does the golden rule apply to every elderly client?

No. The golden rule is a recommended precaution where there is a real reason to question capacity — advanced age combined with illness, a recent diagnosis affecting cognition, or instructions that depart from a client's known wishes — rather than a blanket requirement for every client over a certain age. Judgement is required, but the safer course where any doubt exists is to arrange an assessment.

Is an LPA capacity assessment enough to show testamentary capacity?

Not on its own. As the case law confirms, capacity to make a lasting power of attorney or other lifetime decisions is assessed under the Mental Capacity Act 2005, while testamentary capacity is assessed under Banks v Goodfellow. The two tests can diverge, so a medical assessment obtained for one purpose should not automatically be relied on for the other.

What happens if a will is challenged for lack of capacity?

The burden generally lies with the person propounding the will to raise a presumption of capacity (usually satisfied by due execution and a rational will), but if a real doubt is raised — for example by evidence of a relevant medical condition — the burden shifts to that party to prove capacity affirmatively. This is where a contemporaneous attendance note and, where obtained, a golden rule assessment, become decisive evidence.

Can solicitors be held liable for failing to follow the golden rule?

A solicitor will not automatically be negligent for failing to follow the golden rule, but a court assessing a professional negligence or contentious probate claim will scrutinise the file closely, and the absence of adequate notes or a capacity assessment where warning signs existed can be difficult to defend. Robust file management is as much about protecting the solicitor and the firm as it is about protecting the client's wishes.

Testamentary capacity disputes are won or lost on the quality of the file built at the time of instruction, not on recollection years later. Keeping up to date with the case law on Banks v Goodfellow and the Mental Capacity Act 2005, and building the golden rule and careful drafting practice into every at-risk instruction, remains one of the most effective ways solicitors can protect both their clients and their practice. For structured CPD on wills, probate and capacity issues, browse Learnsignal's CPD courses for legal professionals.