A validity challenge argues the will should never be admitted to probate at all, because it does not reflect the deceased’s true, free, and informed wishes. These cases are forensic and document-heavy. They often turn on medical evidence and the recollection of the solicitor who prepared the will. Our principal, MaryAnn de Mestre, teaches succession law at Macquarie University and is a court-appointed expert in estate and professional negligence matters.
Validity vs Provision: Know Which Case You Have
A validity challenge and a family provision claim are different cases with different evidence and different court forms. Getting the distinction right at the outset shapes your whole strategy.
| Validity Challenge | Family Provision Claim |
|---|---|
| Argues the will itself is legally defective. | Accepts the will is valid. |
| Seeks to stop the will being admitted to probate. | Seeks a share, or larger share, of the estate. |
| Based on capacity, undue influence, fraud, forgery, or execution defects. | Based on inadequate provision for your maintenance and support. |
The Grounds for Challenging a Will
A will can be challenged in the Supreme Court of NSW on several recognised grounds. The table below sets out each ground and when it applies.
| Ground | What It Means |
| Lack of testamentary capacity | The willmaker did not understand the nature of making a will, the extent of their property, or who might expect to benefit. Common where dementia, delirium, mental illness, or heavy medication was present near the end of life. |
| Lack of knowledge and approval | The willmaker did not actually know or understand the contents of what they signed. This can arise from a drafting error, or where a major beneficiary arranged for the will to be drawn up. |
| Undue influence | Someone coerced the willmaker so the will reflects that person’s wishes, not the willmaker’s own. The law requires the willmaker’s free will to have been genuinely overborne. It is a frequent feature of elder abuse. |
| Fraud | The willmaker was deliberately deceived about facts that led them to make or change their will. |
| Forgery | The signature or the document itself is not genuine. |
| Improper execution | The will was not signed and witnessed as required by the Succession Act 2006 (NSW), and the Court is not satisfied it should dispense with those requirements. |
| Revocation | A later will or codicil exists, or the will was revoked by a subsequent marriage or affected by a divorce. |
Lodging a Caveat: Stopping Probate in Its Tracks
If you learn of a will you believe is invalid before probate is granted, you can lodge a caveat with the Supreme Court of NSW. A caveat prevents a grant of probate while it remains in force, buying time to investigate.
- A caveat remains in force for six months from the date it is filed, unless the Court orders otherwise.
- Once a caveat is in place, the person seeking probate must prove the will in solemn form, and the onus shifts to them to satisfy the Court it is valid.
- Acting before probate is granted, and before the estate is distributed, gives you a far stronger and cheaper position than challenging a will after assets have changed hands.
If probate has already been granted, you can still seek revocation of the grant, but the process is harder and time is critical. Speak with us immediately if you suspect a will that has already gone to probate is not valid.
The Evidence That Wins These Cases
Validity challenges are won and lost on evidence, not impressions. The material we look for early includes:
- Medical records and treating specialists’ notes from around the date the will was signed.
- The file notes of the solicitor who prepared the will, including any capacity assessment.
- Evidence of the willmaker’s presentation from family, friends, carers, and medical staff.
- The history and timeline of any new relationship, carer, or adviser who benefited from the change.
- Earlier wills, to establish a pattern of the willmaker’s genuine intentions.
Costs: What Is at Stake
Costs in these matters are always at the Court’s discretion.
Where a challenge is reasonably brought and the willmaker’s own conduct created the doubt, costs are often paid from the estate. Where a challenge is found to be unmeritorious, the person who brought it can be ordered to pay costs personally.
This is exactly why an honest, evidence-based assessment before filing anything is so important.
Why Clients Choose M de Mestre Lawyers
Validity challenges demand precision, medical literacy, and courtroom judgment in equal measure.
- MaryAnn de Mestre is a sessional academic and Convenor of Succession Law at Macquarie University, and a court-appointed expert in estate and professional negligence matters.
- She was named Academic/Researcher of the Year at the Women in Law Awards and has been a finalist for Partner of the Year in Wills and Estates.
- She has a particular focus on elder abuse, directly relevant where undue influence or capacity is in issue, and is a regular media commentator, featured on ABC Radio, 2SM, and in the Australian Financial Review, The Guardian, and the Sydney Morning Herald.
- We act for people challenging wills and for executors and beneficiaries defending them, so we understand precisely how the other side will build its case.
- We bring a strategic, evidence-led approach, paired with genuine compassion for families navigating one of the most difficult disputes they will ever face.
As a Northern Beaches firm, we combine local accessibility with genuinely specialist expertise, the kind that usually comes only from a lawyer who also teaches this area of law at university level.
Get in Touch
If you believe a will may not reflect the willmaker’s true wishes, or you are an executor facing a challenge to a will you are administering, contact M de Mestre Lawyers promptly. Timing matters more than almost anything else in these cases.
Phone: (02) 9913 1182
Address: 27/90 Mona Vale Road, Warriewood NSW 2102
Web: www.mdemestrelawyers.com.au
Frequently Asked Questions
How much does it cost to challenge a will in NSW?
There is no fixed figure. The Supreme Court filing fee for a probate caveat is modest and reviewed each year on 1 July, but legal costs depend on how contested the matter becomes and how much evidence is needed. Because costs can be ordered against you if a challenge fails, an early assessment of the merits is the best cost control there is.
Who pays if the challenge succeeds?
Costs are always at the Court’s discretion. Where the willmaker’s own conduct created genuine doubt, the estate often bears the costs. A successful challenge does not guarantee the estate will pay, so this should be discussed before you file.
Can a will be challenged after the estate has been distributed?
It is possible but much harder. Once assets have been paid out, you may need to trace them and seek to recover distributions, which adds cost and uncertainty. This is why acting before probate, or at least before distribution, matters so much.
What happens to the estate if the will is declared invalid?
If there is an earlier valid will, that will governs the estate. If there is no earlier will, the estate is distributed under the intestacy rules in the Succession Act 2006 (NSW), which set a fixed order of who inherits.
