7 Will Writing Mistakes That Could Invalidate Your Will

The Wills Act 1837 sets out clear requirements for a valid will. Those requirements have barely changed in 190 years. Yet wills are still challenged, set aside, and declared invalid every year — most often because of errors that are entirely avoidable.

1. Fewer Than Two Witnesses — or Witnesses Not Present Simultaneously

The law requires exactly two independent witnesses, both present at the same time when you sign. A will witnessed by only one person, or by two witnesses who weren't in the room together, is invalid. There are no exceptions. This is the single most common reason wills fail formal scrutiny.

2. A Beneficiary Acting as Witness

A witness who is also named as a beneficiary in the will — or who is married to or in a civil partnership with a beneficiary — does not invalidate the will itself. But they forfeit their gift entirely. The will stands; their inheritance does not. Always use independent witnesses with no financial interest in your estate.

3. Not Updating After Marriage

Marriage automatically revokes an existing will in England and Wales. A will made before your wedding is legally void from the date of the marriage — unless it was made "in contemplation of" that specific marriage and says so explicitly. This catches many people entirely off guard. If you marry after making a will, you must make a new one.

4. Handwritten Alterations After Signing

Any alteration made to a will after it has been signed and witnessed is legally ineffective unless it has itself been signed and witnessed with the same formality as the original. Crossing things out, making margin notes, or adding clauses after the event will not take effect — and may create ambiguity that leads to a challenge. If you need to change your will, make a new one or execute a formal codicil.

5. No Residuary Clause

A will that distributes specific gifts but has no residuary clause — covering everything not explicitly mentioned — creates what lawyers call a "partial intestacy." Assets not covered by the will fall into the rules of intestacy. This often produces outcomes the testator would not have wanted, particularly for assets acquired after the will was made. Always include a residuary clause.

6. Unsigned Will

A will must be signed by the testator — or by someone else at their direction, in their presence — at or after the end of the document. An unsigned will has no legal effect whatsoever. The signature must appear at a point that makes clear it applies to the whole document. Signing only the first page, for instance, may not be sufficient.

7. Lack of Testamentary Capacity

A will can be challenged on the grounds that the person lacked testamentary capacity at the time of signing — that they did not understand the nature of the document, the extent of their estate, or the claims of those who might reasonably expect to benefit. Wills made by people with dementia or under the influence of medication are particularly vulnerable to this challenge. An attestation clause that records the testator's capacity provides important protection.

How Wills Assured Protects Against All Seven

Every Wills Assured document includes a compliant attestation clause, a full residuary clause, clear signing instructions, and step-by-step witnessing guidance — specifically designed to prevent each of the errors above. The questionnaire is structured to flag key life events and prompt review when circumstances change.