What Can Make a Prenup Invalid?
Understanding the risks that undermine BFAs — and how to avoid them.
BFAs can be set aside by a court
A Binding Financial Agreement is not immune from challenge. Under section 90K of the Family Law Act 1975, a court can set aside a BFA in a number of circumstances. Understanding these risks is the first step to avoiding them.
The most common grounds for setting aside a BFA are not obscure legal technicalities — they are failures in the process of creating the agreement. Most of them are entirely preventable.
Inadequate or absent legal advice
The most common reason BFAs are challenged is problems with independent legal advice.
The Family Law Act requires each partner to receive genuine independent legal advice from their own solicitor before signing. Courts have set aside agreements where:
• One or both partners did not receive any legal advice • The advice given was brief, superficial, or did not genuinely explain the effect of the agreement • The same lawyer advised both partners • A certificate was signed without a real advice session
The certificate of independent legal advice is not just a formality. It must reflect a genuine consultation where the solicitor explained the agreement and its implications to their client.
Incomplete or false financial disclosure
A BFA can be set aside if one partner failed to disclose a material financial matter, or actively misrepresented their financial position.
Examples include:
• Failing to disclose a property, investment, or business interest • Understating the value of assets • Not disclosing significant debts • Concealing an expected inheritance
The Family Law Act treats non-disclosure seriously. If a court finds that one partner's financial picture was materially incomplete or misleading at the time of signing, it has grounds to set the agreement aside — regardless of whether the other party had independent legal advice.
Duress, undue influence, or unconscionable conduct
An agreement must be entered into voluntarily. If one partner was pressured into signing — or if the circumstances were so one-sided as to amount to unconscionable conduct — the agreement can be challenged.
Common risk factors include:
• Presenting the agreement very close to the wedding date, when one partner feels they cannot say no • One partner having significantly more legal and financial knowledge • Emotional pressure, threats, or manipulation • One partner being in a financially or emotionally vulnerable position
This is why Prenuply's process involves adequate time for both partners to review the agreement and receive independent advice — not a last-minute signature under pressure.
Significant hardship — especially involving children
A court can also set aside a BFA if circumstances have changed since signing in a way that makes the agreement grossly unfair — particularly where there is a child of the relationship.
For example, if a couple had no children when they signed the agreement, but later had children and one partner gave up their career as carer, a court may find that enforcing the original BFA would cause significant hardship.
This does not mean BFAs cannot address circumstances involving children — but it does mean that the possibility of future children and changed circumstances is worth discussing with your lawyer.
The lesson: process matters as much as content
Many couples focus on the content of a BFA — what assets are covered, what happens on separation. But in practice, the most common vulnerabilities are in the process, not the terms.
A BFA prepared with full financial disclosure, genuine independent legal advice from experienced family lawyers, adequate time for both parties to review and understand the agreement, and proper execution is a much stronger document than one that cuts corners on any of these steps.
Premuply's process is designed specifically around these requirements.