Making a will is one of the most important things you can do for the people you care about. For that will to be valid, the person making it must have what the law calls testamentary capacity. Understanding what this means, and taking a few sensible steps, can help make sure a will reflects a person’s true wishes and holds up if it is ever questioned.

What does testamentary capacity mean?

Testamentary capacity means that a person has the legal and mental ability to make a valid will. In simple terms, the person making the will must understand what a will is, what they own, and who may reasonably expect to receive something from their estate.

You do not need perfect health or memory

In New South Wales, a person does not need to have perfect memory or be in perfect health to make a will. A person can have some memory loss, be elderly, or have a medical condition and still have testamentary capacity. What matters is whether they understand the important decisions they are making at the time they make the will.

What the will-maker needs to understand

A person making a will should generally be able to understand:

• that they are making a will, and that the will decides what happens to their property after they die;
• the general type and value of the property they own, such as a house, bank accounts, shares, superannuation, or personal items;
• the people who may expect to receive something from their estate, such as a husband, wife, partner, children, or dependants;
• the effect of leaving someone out of the will, or giving one person more than another;
• the reasons for the decisions they are making.

Some examples

A few simple scenarios help show how this works in practice.

Consider an 82-year-old woman who sometimes forgets names or appointments. She still understands that she owns a home, has money in the bank, and has three children, and she says she wants to leave everything equally to those children. She is likely to have testamentary capacity, even though she has some memory problems.

Now consider a person with advanced dementia who cannot remember that they own a house, does not recognise their children, and cannot explain what a will does. That person may not have testamentary capacity.

A person with early-stage Alzheimer’s disease may be confused on some days but clear on others, able to talk about their family, their home and their wishes. If they make a will on a day when they understand these matters, they may still have testamentary capacity.

Finally, consider a person who decides to leave more to one child because that child has cared for them for many years. They understand that their other children may be upset, but they can clearly explain their reasons. This may support the view that they have testamentary capacity.

Why testamentary capacity matters

Testamentary capacity is important because a will can be challenged after a person dies if there are concerns that the person did not understand what they were doing. A challenge like this can cause stress, delay, and legal costs for the family, often at an already difficult time.

When concerns about capacity often arise

Questions about capacity are more likely to come up where the will-maker is elderly or seriously ill; where they have dementia, memory loss, or another cognitive condition; where the new will is very different from an earlier one; where one family member receives much more than others; or where someone close to the will-maker appears to be pressuring or influencing them.

Keeping good records can help

If there may be questions about capacity, it is helpful to keep clear records. This may include notes of the will-maker’s instructions, the reasons for their decisions, and, where appropriate, a medical assessment. These steps can help show that the will-maker understood their choices when the will was made.

How Complete Legal can help

We help people prepare valid wills that reflect their wishes and reduce the risk of a later dispute, including taking extra care to document the process where capacity may be questioned. If you are worried about a loved one’s will, or a will that has already been made, we can talk you through the options.

This article is general information only and is current as at July 2026. It does not take your personal circumstances into account, and it is not legal advice. You should seek advice tailored to your situation.

If you are planning your will, or you have concerns about a will and testamentary capacity, get in touch to discuss your situation.