What Makes a Will Legally Valid?

Section 9 of the Wills Act 1837 sets out four core requirements. The will must be in writing. It must be signed by the testator, or by someone else in their presence and at their direction. The testator must intend, by signing, to give effect to the will. And the signature must be made or acknowledged in the presence of two witnesses who are both present at the same time, each of whom must then also sign the will in the testator's presence.

These formalities exist to reduce fraud and disputes, by making sure there is clear, witnessed evidence that a particular document reflects the testator's genuine intentions at the time of signing.

It is a common misconception that a will must be witnessed by a solicitor or other professional. In fact, any independent adult can act as a witness, including a neighbour, colleague or friend, provided they are not a beneficiary or married to one, and provided they are physically present to see the will signed.

Beyond the formal signing requirements, the testator must have testamentary capacity at the time the will is made. This means understanding, in broad terms, what a will is and its effect, roughly what they own, and who might reasonably expect to benefit from their estate, without being affected by any disorder of the mind that distorts these judgements.

Capacity is assessed at the time the will is signed, not at some earlier or later point, which is why a diagnosis such as early-stage dementia does not automatically prevent someone from making a valid will. What matters is whether they understood the relevant matters at that specific moment, and in cases of doubt, a solicitor may arrange for a doctor to assess and record capacity at the time of signing.

The testator must intend to make this particular will, understanding and approving its contents, and must not be acting under undue influence or pressure from another person. A will made because someone was coerced or misled can be challenged and set aside, even if it was signed and witnessed correctly.

A witness (or their spouse or civil partner) should not be a beneficiary under the will. If they are, the will itself usually remains valid, but the gift to that beneficiary can be invalidated, which is why it is important to choose independent witnesses who have nothing to gain from the document.

A properly made new will, including a standard revocation clause, cancels any earlier will. Marriage also automatically revokes an earlier will unless it was made in contemplation of that marriage, which is a common reason people find their existing will is no longer valid without realising it.