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 Texas, testamentary capacity is defined as the legal and mental ability of a person to create a valid will. This includes understanding the nature of the act, the extent of their property, and the disposition of their assets upon death. Texas law presumes that adults have the capacity to make a will, but minors typically do not, unless they are married or have served in the military. The Texas Estates Code governs issues of testamentary capacity. Challenges to a will based on lack of testamentary capacity must be proven by the party contesting the will. The standard for testamentary capacity in Texas is relatively low; the testator must simply understand the business in which they are engaged, the nature and extent of their property, and the manner in which they are distributing their assets. The historical terms 'of sound mind and memory' or 'of sound mind and disposing memory' are reflective of the testator's mental state and are sometimes included in the will itself as a declaration of capacity.