To make a valid will, you need to be able to fully understand what it is you’re doing and what the consequences will be. The legal term for this is ‘testamentary capacity’. Here, we’ll take a good look at how testamentary capacity works and how it’s proved – or disproved – when a will is made or contested.


What is testamentary capacity?

Testamentary capacity is a legal term used to refer to someone’s ability to understand what they’re doing when they make or change their will.

You need to have testamentary capacity to make a valid will. If it can be proved that you weren’t able, given your mental state, to really understand what you were doing, your will can be contested. Helpfully, there’s an established testamentary capacity checklist that judges use to evaluate such claims.


What’s the testamentary capacity test?

The test for testamentary capacity was established in an 1870 court case, Banks v Goodfellow. It says that the person making the will (the testator) must:

  • Understand what it means to make a will and what the result will be
  • Understand the extent of the estate they are passing on through the will
  • Appreciate that there are people who might reasonably expect to inherit some of their estate (whether these people are beneficiaries or not doesn’t matter)
  • Not be suffering from a mental illness that would cause them to make bequests that they might not have otherwise made

This testamentary capacity assessment is usually quite generous. If a will is contested, the testator is assumed to have had capacity until the person contesting it can raise real doubt that this is the case.

That said, if the person contesting the will manages to raise real doubt, it’ll be up to the person upholding the will to prove that the testator fully understood what they were doing.


Banks v Goodfellow

In the case of Banks v Goodfellow, the person who made the will, John Banks, suffered from a mental illness and spent some time in an asylum. While Banks was free when he made the will, he still harboured a strong conviction that he was being persecuted by a man called Featherstone Alexander.

In this case, Banks’ will was found valid on the basis that while he was deluded, those delusions didn’t affect the bequests in the will. The case may have ended differently if Banks had left money to Featherstone Alexander.


Proving testamentary capacity when you’re making a will

If you’re elderly or unwell, it’s worth thinking about ways to make your testamentary capacity clear when you’re writing your will.

There are no specific kinds of evidence that a judge will be looking for. But here are a few tips:

  • Consider asking your GP or another doctor who knows you well to witness the signing of your will, or to write a letter stating that they believe you to be mentally competent
  • Talk honestly about your wishes with your close family and friends when you make the will, if you can – and put it in writing
  • Make sure that whatever you communicate about your wishes is consistent – don’t tell different people different things
  • If you’re giving money to a cause or a charity, talk to your family about why this is so important to you
  • Make sure all the names and contact details in your will are complete and spelled correctly


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