The legal and mental competence required to execute a valid will. Generally requires the testator to understand the nature of making a will, the extent of their property, the natural objects of their bounty (family), and how the will distributes their estate. The standard is lower than general contractual capacity.
Testamentary capacity means you're mentally capable of making a will. Under the test established in *Banks v Goodfellow* (1870), which Australian courts still apply, you need to understand four things at the time you sign: (1) that you're making a will and what that means, (2) broadly what assets you own, (3) who might reasonably expect to benefit (your family and dependants), and (4) how your will distributes your estate.
The threshold is lower than for signing contracts—people with some cognitive decline may still have testamentary capacity on a given day. However, capacity can fluctuate, and a court will assess whether you had capacity at the specific time you signed.
⏱ When you'll encounter this term
- Contesting a will based on lack of capacity
- Making a will while elderly or ill
- Doctor assessments before will signing
- Probate disputes over testator's mental state
"My uncle contested Grandma's will, claiming she lacked testamentary capacity due to dementia. But her lawyer had her examined by a doctor before signing, who confirmed she understood her assets, her family relationships, and what the will did—that was enough for testamentary capacity."
⚖️ Compare: Testamentary Capacity vs Contractual Capacity
Lower threshold. For wills only. Understand assets, family, will's effect. Can have despite some impairment.
Higher threshold. For contracts, deeds. Full understanding of complex terms. More stringent requirements.
💡 Why this matters
If you lack testamentary capacity when making a will, the will may be invalid—but this is ultimately for a court to decide if challenged. Capacity isn't all-or-nothing: someone with dementia or mental illness may still have capacity on particular days or at particular times. This is why timing matters.
Getting a medical assessment at the time of signing provides valuable evidence if the will is later challenged, but it doesn't guarantee a court will find capacity existed. Courts consider all the circumstances.
⚠️ Common mistakes
- Assuming someone with a diagnosis automatically lacks capacity—diagnosis doesn't equal incapacity
- Not getting a doctor's assessment when capacity is questionable, leaving the will vulnerable to challenge
- Confusing testamentary capacity with contractual capacity—the will threshold is much lower
- Making a will during a hospital stay or medication that affects cognition without documenting a lucid moment
💡 Did you know?
The test for testamentary capacity was established in 1870 in the famous English case Banks v Goodfellow and is still used in many common law countries today. It's deliberately set at a low threshold to allow people to make wills even if they have some cognitive decline.