What Makes a Will Invalid in England and Wales?

Does a person need mental capacity to make a valid will?

Yes. The testator must understand what a will does, the extent of what they own, and who might reasonably expect to benefit from it. This is called testamentary capacity, the most common ground a will gets challenged on.

The test comes from a long-established legal case, Banks v Goodfellow. It asks whether the person understood they were making a will and roughly what they owned. They must also weigh up who had a claim on their estate, without their judgment distorted by delusion or illness. Age or a diagnosis like dementia does not automatically mean someone lacks capacity, and capacity can vary over time. Where there is any doubt, solicitors are trained to get a contemporaneous medical opinion before the will is signed, precisely to avoid this challenge later.

What happens if a will is not signed and witnessed correctly?

A will that is not properly signed and witnessed can be entirely invalid, regardless of how clearly it sets out the testator’s wishes. This is a formal requirement under the Wills Act 1837, not a matter of interpretation.

The testator must sign in the presence of two independent witnesses, who then sign in the testator’s presence too. Common errors include using only one witness, a witness who is also a beneficiary, which cancels that person’s gift rather than the whole will, or witnesses signing at different times rather than together. Correct execution is one of the easiest requirements to get right and one of the most common ways homemade wills fail.

What does “lack of knowledge and approval” mean?

The testator must actually know and approve what is in their will, in full, not just sign it without reading it properly. Where someone else prepared the will and stands to benefit, the court looks more closely at whether the testator genuinely understood its contents.

This ground often overlaps with capacity and undue influence, but it is legally distinct. A person can have full mental capacity and still not have properly understood or approved specific terms that were inserted or changed without their knowledge. Having the will read aloud to the testator, or a solicitor confirming they understood it before signing, creates a presumption that they did know and approve its contents.

What is undue influence, and how hard is it to prove?

Undue influence means someone coerced the testator into writing a will that does not reflect their genuine, freely made wishes. Courts set a high bar for proving it, and there is no presumption that it happened just because a will looks unfair.

The person challenging a will on these grounds must show actual coercion, not just that a relationship existed where influence was possible. Normal family discussion or persuasion about inheritance is not undue influence. What counts is evidence the testator’s free will was actually overpowered by pressure. This could mean threats, isolation, or exploiting dependency on a carer, changing their real decisions about who should benefit. This is one of the hardest grounds to prove, and cases can take years to resolve.

Can a will be forged or fraudulent?

Yes, though uncommon. A will is invalid if forged, the signature is not genuine, or the testator was deliberately deceived about what they signed. A related problem is poisoning the testator’s opinion of a beneficiary, called fraudulent calumny.

Suspected forgery often centres on a signature that looks inconsistent with the testator’s genuine signature elsewhere. Fraudulent calumny is different again: it is not about the document itself, but about someone deliberately feeding the testator false information to turn them against a beneficiary who would otherwise have inherited. Both are taken seriously by the courts, and executors who suspect either should get advice quickly, since evidence can be lost over time.

What happens if a will is declared invalid?

If a will is successfully challenged, an earlier valid will takes its place, or the intestacy rules apply if none exists. The challenge itself does not decide who inherits, only whether this document is valid.

Courts do not write a new will for the deceased. They simply decide whether the disputed document is valid. If it is not, and a properly executed earlier will exists, that earlier will governs the estate. If no valid will exists at all, the intestacy rules apply, which can produce a very different outcome from what anyone actually wanted, including cutting out an unmarried partner entirely.

Frequently asked questions

How can you prove a will is invalid?

Evidence depends on the ground. Capacity challenges usually need medical evidence and witness statements about the testator’s state of mind. Undue influence and fraud need clear evidence of coercion or deception, since courts do not accept a will looking unfair as proof on its own.

What automatically invalidates a will?

Marriage or civil partnership automatically revokes an existing will in England and Wales, unless it was made in contemplation of that marriage, and divorce also affects gifts to a former spouse. Revoking a will covers this and the other ways a will is cancelled deliberately or automatically.

What are the conditions for a will to be valid?

The testator must be 18 or over and have testamentary capacity. The will must be in writing, signed by them, and witnessed by two people present at the same time who then sign in the testator’s presence. Missing any of these can invalidate the will.

Why would a will not be valid?

The most common reasons are incorrect witnessing, the testator lacking mental capacity, or someone contesting that the testator did not know and approve its contents. Undue influence and forgery are rarer but more serious, and both require strong evidence to prove.