Testamentary Capacity

Testamentary capacity is the mental capacity a person must have at the time they make a will for that will to be valid. The Law Commission's 2025 report on wills law, published through the Ministry of Justice, confirms that the test of capacity is currently governed by the 1870 case Banks v Goodfellow, and that this common law test still applies wherever a solicitor or will writer is contemporaneously assessing whether a testator has capacity to make a will.

In Banks v Goodfellow, Chief Justice Cockburn set out what a testator must be able to do: understand the nature of the act and its effects, understand the extent of the property being disposed of, and comprehend and appreciate the claims to which they ought to give effect. The Law Commission's report quotes the judgment directly, recording that a testator shall understand the extent of the property of which he is disposing; shall be able to comprehend and appreciate the claims to which he ought to give effect, and that no insane delusion shall influence his will in disposing of his property and bring about a disposal of it which, if the mind had been sound, would not have been made.

The Law Commission's report notes that this test is commonly divided into three or four limbs, in summary requiring that the testator has the capacity to understand that they are making a will, and the effect of their testamentary disposition. Reform is under active consideration: the Government's response to the Law Commission's report, given by the Minister for Courts and Legal Services, describes proposals for a new Code of Practice for Testamentary Capacity to assist in assessing whether someone is of sound mind to make a will, alongside a possible move to align the test with the Mental Capacity Act 2005 — but Banks v Goodfellow remains the applicable common law test unless and until that reform is enacted.