Testamentary capacity is the legal and mental ability of a person making a will (the testator) to make a legally binding disposition of their assets and to understand the nature and effect of the act of making a will—including disposing of their assets at death.

Proof of testamentary capacity is a required element of a will being admitted to probate and recognized by the court as having legal effect.

Adults are generally presumed to have the legal capacity to make a will, but minors (persons under a certain age) are not—with some exceptions in some states, such as if the minor has served in the military or has been married.

Persons who suffer from dementia, Alzheimer’s disease, or insanity, for example, may lack testamentary capacity to make a will.

In legal jargon, the historical terms of art for testamentary capacity were that the testator was “of sound mind and memory” or “of sound mind and disposing memory,” and this terminology is sometimes recited in a will as a statement of the testator regarding the testator’s mental capacity when making the will.

Laws vary from state to state and the requirements related to testamentary capacity are often located in a state’s statutes—usually in the estates code or probate code—and interpreted and applied by the courts in specific factual circumstances or cases that are reported in court opinions involving will contests, for example.

In New Hampshire, testamentary capacity is the legal and mental ability of an individual (the testator) to create a valid will. This includes the ability to understand the nature of the act, the extent of their property, and the disposition of their assets upon death. New Hampshire law presumes that adults have the testamentary capacity to make a will, while minors typically do not, unless specific exceptions apply. The state's statutes regarding testamentary capacity can be found in the New Hampshire Revised Statutes Annotated (RSA), specifically in the provisions related to wills and estates. Individuals with cognitive impairments, such as dementia or Alzheimer's disease, may be deemed to lack testamentary capacity, depending on the severity of their condition. The historical standard for testamentary capacity in New Hampshire involves being 'of sound mind,' which is sometimes explicitly stated in the will itself. The determination of testamentary capacity is ultimately made by the probate court when a will is submitted for probate, and the court may consider evidence and testimony to decide if the testator had the requisite capacity at the time the will was executed.