Making a Will is one of the most important steps you can take to protect your wishes and provide for the people you care about. Unfortunately, not every Will holds up when it matters most. When a Will is found to be invalid, the consequences can be costly and leave families in conflict at an already difficult time.
Our 2025 Inheritance State of Play Report found that 42% of Western Australians either have no Will at all or have one so out of date it no longer reflects their current circumstances. In those cases, the risk of disputes and unintended outcomes is high.
If you’ve ever wondered what can make a Will invalid (and how to avoid those traps), this guide is for you.
What makes a Will valid in Western Australia?
In WA, the starting point for a valid Will is set out in the Wills Act 1970 (WA). For a Will to be legally recognised, a Will must meet the following legal requirements:
- Be in writing, whether typed or handwritten
- Be signed by the Will-maker (also called the testator)
- Be signed in the presence of at least two witnesses, who must also sign the Will in the presence of the Will-maker and each other
These rules help ensure that the document reflects the Will-maker’s true intentions and that it has not been altered or created under suspicious circumstances.
Dating a Will is also important – however an undated Will does not automatically make it invalid. An undated or mis-dated Will just adds to the work needed to prove the Will in a probate application.
There are some exceptions. The Supreme Court of Western Australia has the power to accept an “informal” document that does not strictly meet these requirements as a valid Will, but only if it is satisfied that the document clearly records the deceased’s intentions. While these provisions can save some Wills from being thrown out completely, relying on these powers as a safety-net is risky, and often leads to disputes.
Above all, a valid Will depends on the Will-maker having “testamentary capacity” at the time it is made. We explain this in more detail in the next section.
Common reasons a Will can be invalid
1. Lack of testamentary capacity
The Will-maker must be of sound mind when the Will is made, and the test includes some key steps. A Will-maker must:
- Understand that they are creating a Will and what that means
- They must have a general idea of the assets they own
- Know who might reasonably expect to benefit from their Will
- Not be suffering from any disorder of the mind that ‘poisons’ their affections towards a beneficiary.
Loss of capacity is increasingly common in later life, particularly with illnesses such as dementia. General age and infirmity can also play a part. A Will signed when the person did not have testamentary capacity can even be set aside entirely.
2. Undue influence or coercion
A Will must reflect the true wishes of the Will-maker, not the demands of someone else. If a person pressures, manipulates or intimidates them into making or changing their Will, this is called undue influence. These cases can be hard to prove because the pressure often happens behind closed doors, but they are a regular cause of disputes.
3. Fraud or forgery
If a Will is faked, altered, or signed by someone other than the Will-maker without their consent, it can also be thrown out. Fraud might involve misleading someone into signing a document they do not realise is a Will, changing pages after it has been signed, or writing in a false signature on a document altogether.
Forgery can be uncovered through handwriting analysis, witness statements, or other evidence.
4. Failure to meet formal requirements
If a Will is not signed, witnessed or written in accordance with the Wills Act 1970 (WA), it is at risk of being invalid.
As set out above, while the Court can sometimes accept an informal document as a Will, this process is complex and open to being contested.
Relying on an improperly executed document or other informal documents such as notes in apps, unsent emails or voice messages, can leave families with the burden of lengthy legal battles.
5. Lack of knowledge or approval
A Will-maker must know and approve of what is written in their Will. If the contents are hidden from them, or if suspicious circumstances suggest they did not fully understand the document, the Will can be challenged. This often arises when the Will was prepared by someone who stands to gain a significant benefit.
Even common issues such as age, poor eyesight, deafness and language barriers can mean that a person is unable to properly understand and approve of the terms of their Will.
6. Not the final Will
Only the most recent valid Will applies. If an earlier Will is mistakenly treated as the last one, or if multiple versions are found, disputes can arise over which document should be followed.
7. Impact of marriage, divorce, or death of a beneficiary
In WA, a marriage or divorce revokes a Will unless it was made in anticipation of that marriage or divorce.
The death of a beneficiary can leave parts of a Will ineffective, if there are no substitution provisions in place. If these issues are not addressed promptly, the Will may fail to operate as intended.
8. Alterations and the condition of the Will
Altering a Will can affect its validity. Your Will must also be kept in a pristine condition. Actions such as writing on it, marking it, removing pages, un-stapling or unbinding it can raise serious questions about whether the Will is the final version intended to apply. As a result of this, Will-makers are advised never to attempt ‘DIY’ changes to their Will once it’s signed.
What happens if a Will is found invalid in Western Australia?
If the Supreme Court of WA decides a Will is invalid, an earlier WIll can be revived and re-instated.
If no earlier Will exists, the person is treated as having died intestate, meaning their deceased estate is divided according to the formula in the Administration Act 1903 (WA).
The intestacy formula is fixed, and prioritises certain close relatives, starting with a spouse or de facto partner, then children, and then more distant family members. This formula takes no account of personal relationships or the Will-maker’s intentions, which is why an invalid Will can lead to outcomes the person never wanted and often to disputes between those left behind.
There is also no choice of executor to manage the estate or choices of who is to receive certain assets. Intestate estates are always more expensive to manage and likely to lead to dispute.
For a deeper look at how intestacy works, read our guide: What Happens if You Die Without a Will in Australia?
How to avoid an invalid Will
While no Will is completely challenge-proof, there are steps you can take to greatly reduce the risk of it being declared invalid:
- Have your Will drafted by a qualified Wills and estate lawyer
- Ensure it is signed and witnessed correctly in line with WA law
- Choose independent witnesses who are not beneficiaries
- Update your Will after major life changes
- Destroy outdated versions once a new Will is signed
- Keep your Will in a safe but accessible place
- Consider including a Testamentary Trust for extra clarity and asset protection
- Communicate your intentions to your family to reduce the risk of disputes later
A well-prepared Will not only stands up legally but also provides your loved ones with certainty at a time when they need it most.
Protect your Will and your legacy
Too many Wills in Western Australia fail when they are needed most because they were drafted without proper advice, signed incorrectly, or left to gather dust for years without being updated. DIY Wills and outdated documents may seem like a shortcut, but they can create far bigger problems for the people you leave behind.
Working with experienced Wills and estate lawyers in Perth gives you the best chance of having a Will that is both legally sound and reflective of your true wishes.
If you are unsure about the validity of your current Will, or you simply want the peace of mind that comes from knowing it will hold up when it matters, we can help.
