Prenups in Australia, and what actually makes one hold

What a prenup is

A binding financial agreement is a contract between two people who are planning to marry, are married, are entering a de facto relationship or are already in one.

It records the assets and liabilities each person brings in, and it records what the parties agree will happen to those assets and liabilities if they separate.

In substance, you are agreeing up front to things that would otherwise be argued about, negotiated or decided by a court after separation.

The Family Law Act deals with agreements for married couples and for de facto couples in separate parts, but the requirements are broadly the same.

What makes one binding

Five things have to be right.

1. The agreement is in writing and signed by both parties.
2. Each party signs voluntarily, free of pressure, coercion or threats.
3. Each party gives full and frank disclosure of their financial circumstances.
4. Each party receives independent legal advice from an Australian legal practitioner before signing, about the effect of the agreement on their rights and about its advantages and disadvantages. The practitioner provides a signed statement confirming that advice was given, and each party gets a copy.
5. The agreement otherwise complies with the requirements of the Family Law Act 1975 (Cth) and has not been terminated or set aside.

Independent means independent. The same firm cannot advise both sides.

When a court will set one aside

Start from the position that a properly prepared agreement will hold. The grounds for setting one aside are specific, and most of them trace back to a failure in the process.

• Fraud. Typically non-disclosure. If one party hid an asset, an interest or a liability, the agreement is exposed.
• Duress or undue influence. Producing the document days before the wedding is the classic example. So is telling someone the wedding is off unless they sign.
• No real opportunity to negotiate. A party who was not given time to consider, take advice and propose changes has an argument.
• Defective legal advice. No advice, or advice that was not independent.
• A material change in circumstances relating to a child. Where the agreement made no provision for children the parties have since had, and one party would suffer hardship as a result, the court can set it aside.
• Unconscionable conduct by one party in obtaining the agreement.

That is not an exhaustive list. It is the list that produces most of the litigation.

What can go in one

• Quarantining assets brought into the relationship, so they stay with the person who brought them in, while wealth accumulated during the relationship is divided.
• Setting the financial settlement in advance, sometimes on a sliding scale that changes with the length of the relationship.
• Protecting specific property with a particular significance, such as family heirlooms, rural land or an interest in a family business.
• Dealing with spousal maintenance, subject to the requirements in the Act.

An agreement cannot deal with parenting arrangements. Those are decided by reference to the best interests of the child, and no contract binds a court on that question.

Timing, and the 2025 property changes

You can enter a financial agreement before, during or after a marriage or de facto relationship. Doing it early, and well before a wedding date, removes the most common duress argument.

It is worth understanding what a prenup is displacing. Since 10 June 2025 the property provisions of the Family Law Act have been restructured, with the framework a court applies now set out in section 79(5) for married couples. The list of considerations now expressly includes the effect of family violence on a party’s contributions and on their current and future circumstances.

That restructure is one reason to have an older agreement reviewed. An agreement drafted against the previous framework may still be binding, but the outcome it produces should be tested against the current law.

Do not draft it yourself

Two reasons.

The first is structural. Both parties need independent legal advice for the agreement to be binding, so you cannot avoid lawyers entirely in any event.

The second is that this looks simpler than it is. The document has to work years later, against facts nobody has thought of yet, and it has to survive a party who by then has every reason to attack it. The failures we see are almost never about the deal. They are about a missing statement of advice, a disclosure gap or a signature obtained too close to a wedding.

If the point of the agreement is to protect wealth, spend a small part of that wealth having it prepared properly. See our page on binding financial agreements.