What Happens if My Will Is Invalid?

Section 9 of the Wills Act 1837 requires a will to be in writing, signed by the person making it (or signed at their direction), with the intention that the signature gives effect to the will, and signed or acknowledged in the presence of two witnesses who are both present at the same time, each of whom then signs in the presence of the person making the will. Every part of this sequence matters. If the witnesses are not both present together, if the will is signed before or after the witnessing takes place rather than as one continuous event, or if there is only one witness, the will is invalid.

This is by far the most common ground on which a will fails, and it is entirely a matter of process rather than judgement. Our guide on how to sign a will sets out the correct sequence step by step, and it is worth following closely even if the rest of the will is straightforward.

To make a valid will, a person must have testamentary capacity at the time it is signed. The long-standing legal test comes from the 1870 case of Banks v Goodfellow, which requires the person to understand that they are making a will and what that means, to understand broadly the extent of the property they are disposing of, to be aware of the people who might be expected to benefit, such as close family, and to be free of any disorder of the mind that distorts their sense of right or perverts their judgement about who should benefit.

Capacity concerns arise most often with older or seriously unwell testators, and can be raised after death by someone who feels the will does not reflect what the person would really have wanted. Where there is any doubt about capacity, it is good practice to have a medical assessment carried out and recorded at the time the will is made, which is one of the reasons a solicitor is often the right choice for anyone in poor health or with a cognitive condition.

Separately from capacity, a person must have known and approved the contents of their will at the time they signed it. This becomes relevant where someone else was closely involved in preparing the will, such as a family member who stands to benefit and also gave instructions on the deceased's behalf, particularly if the person making the will was elderly, unwell, or had limited ability to read the document themselves.

Wills prepared in suspicious circumstances, for example where a beneficiary drafted the will or arranged for it to be signed without the testator having it clearly explained to them, can be challenged on this basis even where signing formalities were followed correctly.

A will is invalid if the person making it was coerced into its terms rather than expressing their own free wishes. Undue influence is notoriously difficult to prove because it usually happens in private, and the law requires more than showing that someone had influence or a close relationship with the testator; it requires evidence that their free will was actually overpowered.

Claims of undue influence are more common where a testator was vulnerable, isolated, or heavily dependent on the person who benefits most from the will, and where the terms of the will represent a significant, unexplained departure from previous wills or from what family members would reasonably expect.

A forged will, whether the signature itself is forged or the document has been altered after signing, is invalid, though genuine forgery cases are rare and can be difficult to prove without expert document analysis. More commonly, a will is invalidated because it was revoked, either deliberately, by physically destroying it with the intention of revoking it, or by making a later will, or automatically, because marriage or civil partnership revokes an earlier will unless it was made expressly in contemplation of that specific marriage.

Divorce is different: it does not revoke a will, but it treats a former spouse as having died before the testator for the purposes of any gift or executor appointment in their favour, which can unexpectedly leave parts of the will without effect if it was never updated.

If a will is found to be invalid, the law generally treats the estate as if that will had never existed. The first step is to check whether there is an earlier valid will still in existence that was not properly revoked, in which case that earlier will takes effect instead. If there is no earlier valid will, the estate is distributed under the intestacy rules, which follow a fixed order of relatives and take no account of what the deceased actually wanted, potentially excluding an unmarried partner, stepchildren, or close friends entirely.

This is often the most upsetting part of an invalid will for the family involved, because the outcome can be very different from what everyone believed had been arranged, sometimes for a reason as simple as a witnessing error nobody noticed.

Problems with a will are rarely spotted while the person is alive. They typically come to light when the executors apply for probate and either the probate registry raises a query about the will's execution, or a family member who expected to inherit differently raises a concern after seeing the document for the first time. At that point, the will may need to be supported by additional evidence, such as an affidavit of due execution, or it may be challenged formally through the courts.

Because these issues surface at probate, months or years after the will was signed, there is often no way to ask the person who made it what they intended, which is exactly why getting the formalities right at the time matters so much.

Disputing the validity of a will, or defending a will against a challenge, is one of the more expensive and slow-moving areas of private legal work. Cases can take many months or longer to resolve, particularly if they proceed to court, and legal costs can significantly reduce the value of the estate being fought over, sometimes disproportionately to the assets involved. Even where a dispute is resolved without a full trial, the delay alone can leave beneficiaries waiting a long time for an estate to be settled.

These disputes also tend to happen within families at an already difficult time, and the relationship damage can outlast the legal process itself. Avoiding the underlying mistake is almost always better than having a strong case afterwards.

Most of the risks above are avoidable with a careful, methodical approach to making your will. Follow the signing and witnessing rules exactly, using two independent witnesses who are not beneficiaries. Make a will while you are in clear health if possible, and consider a medical assessment if there is any doubt about capacity. Keep records of your instructions and reasoning, particularly if your will departs from what people might expect. Review your will after marriage, divorce, or other major life events, since these can revoke or undermine an existing will without you realising it.

For straightforward estates, a guided online will-writing process reduces the risk of execution errors by walking you through each requirement in order. For anything involving vulnerability, capacity concerns, or a likely family dispute, a solicitor is the safer route. Our step-by-step guide on making your will online and our list of common will mistakes cover this in more practical detail.