Many people don’t realise that even small technical mistakes can make a will invalid. Most of these mistakes are completely avoidable once you understand the rules.
Discover everything you need to know about what makes a will invalid in the UK:
Writing a will is one of the most important steps you can take to protect your family and organise your affairs. However, something that many people don’t realise is that even small technical mistakes can make a will invalid.
In some instances, the entire will becomes invalid. Other times, only part of the will fails, which can still cause serious problems for the people left behind. We often see issues with wills that were written years ago or created without professional guidance. The good news is that most of these mistakes are completely avoidable once you understand the rules.
Let’s look at some of the most common reasons a will may not be legally valid in the UK.
One of the most common reasons a will becomes invalid is incorrect signing. For a will to be legally valid in England and Wales, it must follow very specific signing requirements.
A valid will must:
Sometimes people sign the will with one witness and then ask another person to sign later. Unfortunately, that doesn’t meet the legal requirements. Both witnesses must be present at the same time when the will is signed.
You might think no one would ever notice, but when a will goes through probate, the Probate Registry can sometimes contact the witnesses to confirm how the will was signed. Years later, those witnesses may be asked to confirm that they were present together, they saw the testator sign the will, and they then signed it themselves.
If the witnesses cannot confirm that the process happened correctly, the will could potentially be challenged. That’s why proper signing instructions are essential.
Even when people understand the need for witnesses, another common mistake is choosing the wrong people.
Witnesses must meet certain requirements. They must:
If the beneficiary, or their spouse, witnesses the will, there are consequences. The will itself usually remains valid, but the gift to the beneficiary becomes invalid. In other words, the person who was meant to inherit may lose their inheritance entirely.
For example, let’s say that someone leaves their estate equally to two children. If one child’s spouse witnesses the will, the gift to that child becomes invalid. The result could be that the entire estate passes to the other sibling instead. You can imagine how easily that could cause family disputes.
That is why witnesses should always be completely independent – neighbours, colleagues, or friends are usually the safest choices.
Another rule that surprises many people is that marriage usually revokes a will automatically. In England and Wales, when someone gets married, any previous will typically becomes invalid unless the will specifically states it was made “in contemplation of marriage”.
That means if you write a will while you’re single and then later get married, your will may no longer apply. At that point, if you were to pass away without making a new will, your estate would fall under the rules of intestacy, which is the government’s default system for distributing estates.
This can lead to outcomes that are very different from what you originally intended, such as:
Because of this rule, we always encourage people to review their will if they become engaged or plan to marry.
Every valid will should appoint at least one executor. An executor is the person who is responsible for carrying out your wishes after you die. Their role can include applying for probate, collecting assets, paying debts, or distributing the estate to beneficiaries.
If a will doesn’t appoint an executor, it creates a practical problem. Someone still has to administer the estate, so the court will appoint someone to take on that role. This doesn’t necessarily invalidate the entire will, but it does mean that additional steps may be required, the process may take longer, and the person appointed might not be the person you would have chosen.
Naming executors, and ideally backup executors, helps avoid these delays and keeps the process smoother for your family.
Another surprisingly common issue appears in wills that only list specific gifts. For example, a will might list:
That might seem clear, but there’s a potential problem. What happens if the person dies with other assets that weren’t listed? Perhaps they opened a new savings account, inherited money later in life, or owned something that wasn’t specifically mentioned.
If the will doesn’t contain a residual estate clause, which includes wording such as “I leave the rest of my estate to…”, then anything not mentioned falls outside the will. Those assets would then be distributed under the rules of intestacy instead.
This situation is known as partial intestacy, and it can lead to outcomes the person never intended.
Although less common, a will might be challenged if there are concerns about mental capacity or undue influence.
For a will to be valid, the person making it must have the mental capacity to understand the nature of making a will, the extent of their assets, and who might reasonably expect to benefit from their estate. If someone lacked mental capacity at the time the will was made, the document could be declared invalid.
Similarly, if someone was pressured or coerced into making certain decisions, their will may also be challenged. These situations can lead to disputes, especially if family members believe someone influenced the person unfairly.
Professional estate planning helps reduce these risks by documenting the process carefully.
In our experience, many invalid or problematic wills share one thing in common: they were written without professional guidance.
DIY wills may seem straightforward, but estate planning involves more legal rules than many people realise. Small technical mistakes, particularly around witnessing or wording, can create significant problems later.
When a will turns out to be invalid, families often face:
This can all be avoided with proper drafting.
Most invalid wills aren’t caused by complicated legal issues. They’re usually the result of small technical mistakes that could easily have been avoided. To take away, what makes a will invalid is usually:
At Heritage Estate Planning, we always encourage people to treat their will as an important legal document, rather than something to rush through or complete casually. A correctly drafted and signed will gives your family clarity, protection, and peace of mind, which is exactly what it’s supposed to do.
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