What is testamentary capacity?

A legal term referring to a person’s metal ability to write a will

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Elissa SuhSenior Editor & Disability Insurance ExpertElissa Suh is a disability insurance expert and a former senior editor at Policygenius, where she also covered wills, trusts, and advance planning. Her work has appeared in MarketWatch, CNBC, PBS, Inverse, The Philadelphia Inquirer, and more.

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Testamentary capacity is a legal term that describes someone’s ability to make a will. A last will and testament is a legal document containing instructions as to who receives your assets when you die. To have testamentary capacity, a person must have the mental ability to understand the basic mechanics of how a will works, including what property they own and who their beneficiaries are.

Some people may lack testamentary capacity when their mental competence is compromised, like when they suffer dementia or “insane delusions.” Beneficiaries and unnamed heirs dissatisfied with the terms of a decedent’s will may use this as grounds to contest the will. If the court finds that the testator lacked testamentary capacity when creating the will, it may rule in favor of the challenger.

Just because a person has the capacity to make a will does not mean they have the legal capacity to write other estate planning documents, like a transfer-on-death deed or power of attorney (POA), which may require contractual capacity.

Key takeaways

  • Testamentary capacity is required for a will to be valid.

  • The court determines if someone had testamentary capacity.

  • The terms of testamentary capacity are less strict than contractual capacity.

  • Wills can be contested on the grounds of a lack of testamentary capacity.

What does testamentary capacity mean?

Testamentary capacity is a term used in probate law, which requires that a person making a will meet a certain level of mental competence. To make a valid will, you must follow requirements set out by your state law. One common requirement for the construction of a valid will is that the will writer (testator) is the age of the majority, which is 18 in many states. Another requirement is that the will writer have testamentary capacity.

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A person with testamentary capacity must be able to understand the general significance of the will, including the following things:

  • The property they own

  • Who will inherit their property

  • That the will the transfers property upon their death

  • How all of these components work together

A will is used as part of an estate plan to give away a person’s assets and property, so the testator must be able to comprehend what property and assets they own, as well as their beneficiaries that receive the property.

The person writing a will should also be capable of understanding who would inherit if they died without writing a will. A beneficiary can be a person or an organization, and if there isn’t one named in the will, the court will determine the decedent’s heirs, which may be a surviving spouse, children, family members, and blood relatives.

One reason that wills need to be witnessed is so that a third party can attest to the testator’s mental ability in understanding the above components. Learn more about witnessing a will.

Who determines testamentary capacity?

When someone dies, their will must be proven in court during probate. During this time, beneficiaries or relatives can challenge or contest the will if they did not receive a fair portion of the estate. Common reasons to contest the will include if you believe there was undue influence (someone coerced the testator to write the will) or the decedent lacked testamentary capacity to write it.

The law presumes a decedent to have had sufficient testamentary capacity, so anyone who challenges this presumption has the burden of proving to the probate court otherwise. It can be difficult to prove testamentary incapacity during a will contest, since the decedent may have died years after writing their will. You would likely have to furnish evidence — like testimony and paperwork from a medical professional — that speaks to the testator’s state of mind and mental incapacity during the time of the will's execution, which could've been decades earlier.

Keep in mind someone only needs to have sufficient mental capacity at the time of writing the will. The will won’t be invalidated just because the testator lost testamentary capacity as they grew older.

→ Find out what makes a will invalid

Even if you are able to show the testator was not of sound mind, you may still have to provide evidence that this mental incapacity caused the deceased person to write their will in an irrational or unfair manner that deserves to be thrown out by the court.

When a testator lacks mental capacity

A person’s testamentary capacity could be compromised when their mental ability declines, such as due to mental illness or disorder. Mental incompetence goes beyond forgetfulness in old age. Common signs that indicate a lack of mental competency include:

  • Delusions

  • Dementia

  • Alzheimer's disease

  • Senility from old age

  • Cognitive impairment from drugs, alcohol, or brain injury

Anyone experiencing one of the above symptoms or who has a mental disorder can still write a will, so long as they make it during a lucid interval, when they are not suffering from an insane delusion or other cognitive impairment.

You can consult with an elder law attorney if you have more specific questions about what constitutes mental competency.

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