Advice Admin & Legal What can make a will invalid?

What can make a will invalid?

Author: Eliza, Legacy Adviser at Octopus Legacy
Last updated: 27 March 2026

What Can Make a Will Invalid?

A will is one of the most important documents you'll ever create. It decides who gets what when you die, who looks after your children, and how your wishes are carried out. But if it isn't done properly, it can be challenged or declared invalid — and your wishes may not be followed at all.

If a will is deemed invalid, an older version of the will may take its place. If there's no previous valid will, the rules of intestacy apply instead. That means the law decides how your estate is divided, with no regard for what you actually wanted. Unmarried partners, stepchildren, and close friends could receive nothing.

It's a painfully long, expensive, and drawn-out process that is worth avoiding. The good news is that it's straightforward to get right — especially with a properly structured will-writing service.

The Legal Requirements for a Valid Will in England and Wales

For a will to be legally valid under the Wills Act 1837 (as amended), it must meet several requirements:

The person making the will (the testator) must be 18 or over (with limited exceptions for members of the armed forces on active service)
The testator must have testamentary capacity — the mental ability to understand what they're doing
The will must be made voluntarily, without pressure, force, or manipulation
The will must be in writing (it can be typed or handwritten, but must be a physical document)
The will must be signed by the testator (or by someone else in their presence and at their direction)
The signature must be made or acknowledged in the presence of two witnesses, both present at the same time
Both witnesses must then sign the will in the presence of the testator

If any of these requirements isn't met, the will may be invalid.

Common Reasons a Will Can Be Invalid

1. Improper witnessing

The witnessing rules are one of the most common areas where wills fail. Both witnesses must be present at the same time when the testator signs (or acknowledges their signature). The witnesses must then each sign the will themselves, in the testator's presence.

Who can be a witness? Anyone over 18 who has mental capacity. However, there are important restrictions on who should be a witness:

A beneficiary should not be a witness. If someone named in the will (or their spouse or civil partner) witnesses the signature, the will itself remains valid — but that person's gift under the will is void. They lose their inheritance.
The executor can be a witness, though it's generally better to use independent witnesses to avoid any suggestion of undue influence.
Witnesses do not need to read the will or know its contents. They just need to see the testator sign it.

During the COVID-19 pandemic, temporary changes allowed wills to be witnessed via video link (under the Wills Act 1837 (Electronic Communications) (Amendment) (Coronavirus) Order 2020). These provisions applied to wills made between 31 January 2020 and 31 January 2024. Wills made after that date must be witnessed in person.

2. Lack of testamentary capacity

The testator must have the mental capacity to make a will at the time they make it. This is assessed against the test established in the case of Banks v Goodfellow (1870), which requires that the person:

Understands the nature of making a will and its effects
Understands the extent of the property they're disposing of
Is able to comprehend the claims of people who might expect to benefit
Has no disorder of the mind that influences their decisions

This is one of the most common grounds on which wills are challenged, particularly when the testator was elderly or had a diagnosis of dementia, Alzheimer's, or another condition affecting cognitive function.

A diagnosis of dementia does not automatically mean someone lacks capacity to make a will. Capacity can fluctuate, and a person may have periods where they are able to understand and make decisions. Many solicitors and will-writing services will arrange for a medical practitioner to assess capacity at the time the will is made, creating a written record (sometimes called a "golden rule" assessment) that can help defend the will against future challenges.

If you're concerned about a family member's capacity, or if you're making a will and want to protect it from challenge, asking a doctor to confirm capacity at the time of signing is one of the most effective steps you can take.

3. Undue influence

A will is invalid if the testator was pressured, coerced, or manipulated into making it by another person. This is known as undue influence. It can range from obvious threats to more subtle forms of control, such as isolating the testator from other family members or repeatedly pressuring them to change their will.

Undue influence can be difficult to prove after the testator has died. Courts look for evidence that the testator's free will was overborne — meaning they made decisions they wouldn't otherwise have made.

If you suspect undue influence was involved in the making of a will, legal advice should be sought. The burden of proof falls on the person alleging it.

4. Fraud or forgery

A will is invalid if it was forged, altered after signing, or if the testator was tricked into signing a document they didn't understand was a will (known as fraud). This includes situations where the content of the will was misrepresented to the testator.

Any alterations made to a will after it has been signed must be properly witnessed. Unwitnessed changes are not legally valid and will be ignored by the courts.

5. The will was revoked

A will can be revoked (cancelled) in several ways, including by making a new will, by getting married (which automatically revokes an existing will unless it was made in contemplation of that marriage), or by physically destroying the will with the intention of revoking it.

How to Invalidate Your Own Will

There's one simple way to invalidate your own will: write a new one. Each new will should include a clause revoking all previous wills and codicils.

Destroying your old will (voluntary revocation)

You can revoke a will by physically destroying it — burning it, tearing it up, or shredding it — with the intention of revoking it. If you do this without creating a new will, you'll die intestate. Your estate will be divided according to the rules of intestacy, which may not reflect your wishes at all.

Writing a new will

The better approach is to write a new will that replaces the old one. With Octopus Legacy's will-writing service, you can make changes and submit them for review. Once signed and witnessed, the new will replaces the old one. Remember to destroy previous versions to avoid confusion.

Making a codicil

A codicil is a legal amendment that sits alongside your original will. It must be signed and witnessed in the same way as a will. Codicils work for smaller changes — such as updating an executor or adding a specific gift. For more significant changes, writing a new will is usually better.

Find out more about codicils: What are codicils and how to update your will?

When Does a Will Automatically Become Invalid?

Certain life events can invalidate your will without you doing anything. These are known as involuntary revocation.

Marriage and civil partnership

Getting married or entering a civil partnership automatically revokes any existing will in England and Wales. This is one of the most common ways people end up intestate without realising it. If you don't write a new will after your marriage, the rules of intestacy will apply.

You can avoid this by making a will "in contemplation of marriage" — specifically referencing the upcoming marriage in the will before it takes place. This means the will survives the marriage.

The simplest approach is to write a new will soon after getting married.

Divorce and dissolution of civil partnership

Divorce does not automatically invalidate your will. The will remains valid. However, your ex-spouse or former civil partner will be treated as though they had died on the date the divorce or dissolution was finalised.

This means:

Any gifts left to your ex-spouse in the will fail (unless the will says otherwise)
If your ex-spouse was named as executor, they can no longer act
If the will included a "substitution" clause (for example, "if my spouse predeceases me, their share goes to my children"), that clause would take effect

If your will doesn't include substitution provisions, or if your wishes have changed, writing a new will after divorce is strongly recommended.

Separation (without divorce)

Separation without a formal divorce does not change anything about your will. Your estranged spouse remains entitled to inherit under the existing will, and could also make a claim under the rules of intestacy if you die without one.

Does a Change of Address Invalidate a Will?

No. A change of address for anyone named in the will does not make the will invalid. The relevant person can usually still be identified by name, date of birth, and relationship.

However, keeping addresses up to date makes the administration process smoother and avoids unnecessary delays. If someone moves frequently, you can use a "care of" address instead. Executors, guardians, and beneficiaries do not need to live in the UK — including updated international addresses is good practice.

When Should You Update Your Will?

Life changes faster than most people realise. As a general guide, review your will when any of the following happen:

You get married or enter a civil partnership (your old will is automatically revoked)
You get divorced or separate
You have children or grandchildren
A beneficiary, executor, or guardian dies or becomes unable to act
You buy, sell, or significantly change your property
You receive a significant inheritance or change in financial circumstances
The law changes in a way that affects your estate (such as inheritance tax threshold changes)
You move abroad or acquire assets in another country

Even without a major life event, it's good practice to review your will every three to five years.

Write or update your will with Octopus Legacy

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Frequently Asked Questions

What makes a will invalid in the UK?

A will can be invalid if it wasn't properly witnessed (two independent witnesses must be present when the testator signs), if the testator lacked mental capacity, if they were under undue influence or duress, if the will was forged or fraudulently altered, or if it was revoked by a later will, marriage, or physical destruction. The will must also be in writing and signed by the testator.

Does marriage invalidate a will?

Yes. Getting married or entering a civil partnership automatically revokes any existing will in England and Wales. If you don't write a new will after getting married, the rules of intestacy will apply. You can avoid this by making a will "in contemplation of marriage" that specifically references the upcoming marriage. The simplest approach is to write a new will soon after getting married.

Does divorce invalidate a will?

No. Divorce does not automatically invalidate a will. However, your ex-spouse will be treated as though they had died on the date the divorce was finalised. This means any gifts to them will fail and they can no longer act as executor. If your will doesn't include provisions for this scenario, or your wishes have changed, writing a new will is strongly recommended.

Can someone with dementia make a valid will?

A diagnosis of dementia does not automatically mean someone lacks the capacity to make a will. Mental capacity can fluctuate, and a person may have periods where they understand and can make decisions. The legal test (from Banks v Goodfellow, 1870) requires the person to understand what a will is, what they own, who might expect to benefit, and not be affected by a disorder of mind. A medical assessment at the time of signing can help protect the will from future challenges.

Who can witness a will in the UK?

Anyone over 18 with mental capacity can witness a will. Both witnesses must be present at the same time when the testator signs, then each sign the will themselves in the testator's presence. A beneficiary should not witness the will — if they do, their gift under the will is void. The executor can technically be a witness, but independent witnesses are preferred. Since 31 January 2024, video witnessing is no longer permitted.

What happens if a will is invalid?

If a will is deemed invalid, an earlier valid will may take its place. If there is no earlier valid will, the estate is distributed under the rules of intestacy — where the law decides who inherits. Unmarried partners, stepchildren, and close friends may receive nothing under intestacy rules. The process of resolving an invalid will can be lengthy and expensive.

Can a will be challenged after someone dies?

Yes. A will can be challenged on several grounds, including lack of testamentary capacity, undue influence, improper witnessing, fraud, or forgery. Claims can also be made under the Inheritance (Provision for Family and Dependants) Act 1975 if someone who was financially dependent on the deceased feels they haven't been adequately provided for.

How often should I update my will?

Review your will whenever a major life event occurs — marriage, divorce, having children, a death in the family, a significant change in finances, or buying or selling property. Even without a major event, reviewing your will every three to five years is good practice. Marriage automatically revokes an existing will, so writing a new one after getting married is essential.