**Incapacity** (noun) — The legal state of being unable to make or communicate informed decisions about one's personal, financial, or legal affairs due to mental impairment, physical condition, or other factors. Also called "lack of capacity" or "mental incapacity." When a person lacks capacity, they cannot validly execute legal documents such as wills, enter contracts, or manage their own affairs.
Incapacity means you're unable to make decisions for yourself—whether that's because of illness, injury, age-related decline, or another condition affecting your ability to understand and communicate.
It's not just about having a diagnosis. Legal incapacity is about function: can you understand the nature and effect of the decisions you're being asked to make? Can you retain that information long enough to make a choice? Can you communicate your decision?
Capacity can change over time. Someone might have capacity to make simple everyday decisions but lack capacity for more complex matters like managing investments or making a will. And capacity can fluctuate—someone with dementia might have moments of clarity where they do have capacity, even if they don't at other times.
The law presumes you have capacity unless there's evidence otherwise. But when someone lacks capacity, they need others to make decisions for them—either through arrangements they set up while they still had capacity (like an enduring power of attorney), or through court-appointed guardians or administrators.
⏱ When you'll encounter this term
Incapacity matters in estate planning for two main reasons: when you're making your will, and what happens if you lose capacity later.
To make a valid will, you need testamentary capacity. That means you must understand what a will is, know the extent of your property, and comprehend who has a claim on your estate. If you lack this capacity when you sign your will, the will might be challenged as invalid.
But incapacity can also strike before you die. You might develop dementia, suffer a stroke, or have an accident that leaves you unable to manage your affairs. This is why enduring powers of attorney and advance care directives exist—they let you appoint someone to act for you if you lose capacity, rather than leaving it to a court to appoint someone on your behalf.
If you lose capacity without these documents in place, family members may need to apply to a tribunal or court to become your guardian or administrator. This process takes time, costs money, and removes your choice about who makes decisions for you.
Planning for the possibility of incapacity—even when you're healthy—is one of the most important things you can do to protect yourself and the people who care about you.
**Related terms:** [Capacity](/dictionary/capacity), [Testamentary capacity](/dictionary/testamentary-capacity), [Enduring power of attorney](/dictionary/enduring-power-of-attorney), [Guardian](/dictionary/guardian)
---
Learn More
Related Dictionary Terms
Common Questions