Postnuptial Agreements In Australia: What They Are And When You Need One

A postnuptial agreement in Australia is a type of binding financial agreement made during a marriage under section 90C of the Family Law Act 1975.

It allows married couples to set out how their property, financial resources, and spousal maintenance will be handled if the marriage breaks down.

Postnuptial agreements are legally binding when both parties receive independent legal advice, make full financial disclosure, and sign the agreement voluntarily.

They are becoming increasingly common for Australian couples whose circumstances have changed since their wedding day, and understanding how they work can help you decide whether one is right for your situation.

Why Would You Need a Postnuptial Agreement After Marriage?

Many couples do not think about financial agreements before their wedding, and that is completely normal.

Life moves quickly, and a prenuptial agreement is not always a priority when you are planning a ceremony and starting your lives together.

A postnuptial agreement gives married couples the chance to put formal financial protections in place after the wedding has already taken place.

There are several common situations where a postnuptial agreement makes practical sense.

One of the most frequent triggers is a significant change in one partner’s financial circumstances.

If one spouse receives a large inheritance, starts a successful business, or comes into a windfall of any kind, a postnuptial agreement can protect those assets and make clear that they should remain with the original owner if the marriage were to end.

Without an agreement in place, these assets could be included in the overall property pool and divided by the court during separation proceedings.

Another common reason is entering a second or subsequent marriage.

Couples who have been married before often have children from previous relationships and want to make sure their assets are preserved for those children.

A postnuptial agreement can ring-fence specific property, savings, or superannuation so that those assets pass to the intended beneficiaries rather than being subject to a property settlement with a new partner.

Couples who are experiencing financial tension in their relationship also sometimes turn to postnuptial agreements as a way of creating clarity.

If one partner has taken on significant debt, or if there is disagreement about how finances should be managed, a postnuptial agreement can set out each person’s responsibilities and protect the other from liability.

Rather than creating distrust, many couples find that having these conversations openly and formalising the outcomes actually reduces conflict and provides peace of mind.

How Does a Postnuptial Agreement Work Under Australian Law?

A postnuptial agreement in Australia is governed by section 90C of the Family Law Act 1975.

This section allows married couples to enter into a financial agreement during their marriage that sets out how property and financial resources will be dealt with if the marriage breaks down.

It can also address spousal maintenance, which refers to ongoing financial support from one party to the other after separation.

The agreement is a private contract between the two spouses.

Unlike court orders, it does not need to be approved by a judge.

Instead, it is designed to operate outside the court system entirely, meaning that if the couple does separate, the terms of their agreement will govern how their finances are handled rather than leaving those decisions to a court.

This can save both parties significant time, money, and emotional stress compared to contested court proceedings.

Section 90C(2A) of the Act makes it clear that a financial agreement made during a marriage can be entered into either before or after the marriage has broken down.

This means you do not have to wait until things go wrong to put an agreement in place.

In fact, the best time to create a postnuptial agreement is when both partners are on good terms and can have open, honest discussions about their finances without the pressure and emotion that comes with separation.

A postnuptial agreement can cover a wide range of financial matters.

It can deal with property division, specifying which assets belong to which party and how jointly owned property will be split.

It can address superannuation splitting, outline arrangements for spousal maintenance, allocate responsibility for debts and liabilities, and even include provisions about how family businesses or trust interests will be treated.

The agreement can be as broad or as narrow as the couple chooses, covering all financial matters or focusing on specific assets or issues that are particularly important.

What Can a Postnuptial Agreement Include?

A postnuptial agreement can be tailored to each couple’s specific financial situation and concerns.

The flexibility of these agreements is one of their greatest strengths, as they can address a broad range of financial matters or focus narrowly on particular assets or issues.

Understanding what to include in a binding financial agreement helps couples make sure every important detail is covered.

Property division is typically the centrepiece of most postnuptial agreements.

The agreement can specify which assets are considered separate property belonging to one spouse and which are shared marital assets.

It can set out exactly how real estate, investments, vehicles, bank accounts, and personal property will be divided in the event of separation.

For couples with complex asset structures, such as investment portfolios, multiple properties, or overseas assets, this level of detail provides valuable certainty that would be difficult to achieve through court proceedings.

Superannuation is often one of the largest assets in an Australian couple’s property pool, and postnuptial agreements can include detailed provisions about how superannuation interests will be treated.

The agreement can specify whether each party retains their own superannuation without splitting, outline a formula for calculating any split based on contributions made during the marriage, or set out specific dollar amounts or percentages to be transferred.

Because superannuation splitting involves compliance with both family law and superannuation legislation, getting the wording right is important for enforceability.

Spousal maintenance provisions can also be included.

These clauses set out whether one party will provide financial support to the other after separation, and if so, the amount, duration, and conditions of that support.

It is worth noting, however, that a court retains the power to override spousal maintenance provisions if enforcing them would leave one party unable to support themselves without government benefits.

Debt allocation is another important area.

The agreement can specify which debts belong to which party and protect one spouse from being held responsible for the other’s financial liabilities.

This is particularly relevant when one partner operates a business or has taken on significant personal debt during the marriage.

Business interests and family trusts can also be addressed.

If one spouse is a business owner, the agreement can set out how the business will be valued and treated in the event of separation.

Similarly, interests in family trusts or companies can be dealt with to prevent disputes about whether these assets form part of the property pool available for division.

What Are the Legal Requirements for a Valid Postnuptial Agreement?

For a postnuptial agreement to be legally binding in Australia, it must meet strict requirements set out in section 90G of the Family Law Act 1975.

Failing to meet even one of these requirements can render the entire agreement unenforceable, which would leave both parties without the protections they thought they had in place.

The first requirement is that the agreement must be in writing and signed by both parties.

Verbal agreements, no matter how detailed or well-intentioned, have no legal standing under Australian family law.

The document must clearly state that it is made under section 90C of the Family Law Act, and it must address one or more of the matters specified in that section, such as property division or spousal maintenance.

The second and most critical requirement is that each party must receive independent legal advice from a separate legal practitioner before signing the agreement.

The same lawyer cannot act for both parties.

Each lawyer must explain the effect of the agreement on their client’s rights and outline the advantages and disadvantages of entering into the agreement at that point in time.

This requirement exists to protect both parties from signing something they do not fully understand and to reduce the risk of the agreement being challenged later on the grounds of ignorance or unfairness.

After providing this advice, each legal practitioner must sign a statement confirming that the advice was given.

A copy of each signed statement must be provided to the other party or their lawyer.

These signed certificates of independent legal advice form part of the agreement documentation and are essential to its validity.

If these certificates are missing, incomplete, or if the advice given was inadequate, the agreement can be set aside by a court.

Full and frank financial disclosure is also required from both parties.

Each spouse must provide an honest and complete picture of their financial circumstances, including all assets, liabilities, income, and financial resources.

If one party conceals assets or provides misleading information, the agreement can be challenged and potentially overturned on the grounds of fraud or misrepresentation.

Finally, the agreement must be entered into voluntarily.

If one party can demonstrate that they were pressured, coerced, or subjected to undue influence when signing, a court may set the agreement aside.

The landmark High Court decision in Thorne v Kennedy [2017] HCA 49 made clear that Australian courts will closely examine the circumstances surrounding the signing of any financial agreement and will not uphold agreements that were the product of unconscionable conduct or undue influence, even if the technical procedural requirements were otherwise met.

How Does a Postnuptial Agreement Differ from a Prenuptial Agreement?

The core difference between a postnuptial agreement and a prenuptial agreement is timing.

The following table compares the four main types of binding financial agreements available under the Family Law Act 1975.

A prenuptial agreement, governed by section 90B of the Family Law Act, is entered into before marriage.

A postnuptial agreement, governed by section 90C, is entered into during the marriage.

Despite this difference in timing, both types of agreements serve the same fundamental purpose and are subject to the same legal requirements for validity.

Both prenuptial and postnuptial agreements must meet the requirements of section 90G to be binding.

Both require the agreement to be in writing, both parties to receive independent legal advice, signed statements from each legal practitioner, and full financial disclosure.

The enforceability standards are identical, and both types of agreements can be set aside by a court under the same grounds outlined in section 90K of the Act.

From a practical standpoint, postnuptial agreements can sometimes be easier to negotiate than prenuptial agreements.

Before marriage, there can be an inherent power imbalance, particularly if one partner is relocating to Australia, leaving a job, or making other significant sacrifices to enter the marriage.

The High Court’s decision in Thorne v Kennedy [2017] HCA 49 highlighted exactly this dynamic, where a prenuptial agreement was set aside because the circumstances surrounding its signing involved unconscionable conduct.

During a marriage, both partners are already established in the relationship and may find it easier to have open financial discussions on a more equal footing.

There is one important technical point to be aware of for de facto couples who later marry.

If a de facto couple has entered into a financial agreement under section 90UC of the Family Law Act, that agreement becomes void when the couple marries.

They would then need to enter into a new agreement under section 90C to maintain their financial protections.

This is a detail that catches many couples off guard, so it is important to review any existing agreements when your relationship status changes.

When Is the Best Time to Create a Postnuptial Agreement?

The best time to create a postnuptial agreement is when both spouses are communicating well and are willing to discuss financial matters openly.

Trying to negotiate a financial agreement during a period of conflict or when separation is already being considered can make the process more difficult and can also increase the risk of the agreement being challenged later on the grounds of duress or undue influence.

There are several life events that commonly prompt couples to consider a postnuptial agreement.

Receiving an inheritance is one of the most common triggers, as many people want to ensure that family money or property remains protected and available for their children.

Starting or selling a business is another, as the value of business assets can change significantly over the course of a marriage and both parties benefit from having clear arrangements in place.

A significant increase in one spouse’s income or earning capacity, a career change, retirement planning, or the birth of children can all be good reasons to formalise financial arrangements.

Couples entering blended families often find postnuptial agreements particularly valuable.

When both partners bring children from previous relationships into the marriage, there are competing interests and obligations that need to be clearly addressed.

A postnuptial agreement can ensure that assets intended for children from a prior relationship are preserved, while also setting out fair arrangements for the current partnership.

Without such an agreement, the default position under Australian family law could result in assets being divided in ways that do not reflect either party’s intentions.

It is also worth considering a postnuptial agreement if you previously had a prenuptial agreement that no longer reflects your current circumstances.

Life changes, and an agreement made five or ten years ago may not account for new assets, changed income levels, or additional family members.

A postnuptial agreement can replace an outdated prenuptial agreement, provided all parties to the original agreement are also parties to the new one.

Can a Postnuptial Agreement Be Set Aside or Overturned?

A properly drafted postnuptial agreement is designed to be legally binding and enforceable.

However, Australian courts do have the power to set aside a financial agreement under section 90K of the Family Law Act if certain grounds are established.

The most common ground for setting aside a financial agreement is fraud.

If one party has been dishonest in their financial disclosure, whether by hiding assets, undervaluing property, or failing to disclose income or liabilities, the court can invalidate the agreement.

Full and frank disclosure is not optional; it is a legal requirement, and any failure to comply can undermine the entire agreement.

Duress, undue influence, and unconscionable conduct are also grounds for setting aside a postnuptial agreement.

If one party was pressured into signing, did not have a genuine choice, or was taken advantage of due to a power imbalance in the relationship, the court can intervene.

The decision in Thorne v Kennedy [2017] HCA 49 reinforced how seriously Australian courts take these issues, with the High Court unanimously setting aside both a prenuptial and postnuptial agreement where unconscionable conduct and undue influence were found.

A court can also set aside a postnuptial agreement if there has been a material change in circumstances relating to the care, welfare, or development of a child, and the failure to set aside the agreement would cause hardship to the child or the party caring for the child.

This provision reflects the principle that children’s interests are given significant weight in Australian family law, and that no private agreement should operate to the detriment of a child’s wellbeing.

Failure to comply with the technical requirements of section 90G can also render an agreement invalid.

If one party did not receive independent legal advice, if the certificates were not properly completed, or if the agreement was not correctly executed, a court may find that the agreement is not binding.

This is why it is essential to work with a law firm that understands the strict procedural requirements and ensures every step is followed correctly.

What Are the Key Factors for Ensuring a Postnuptial Agreement Holds Up?

Creating a postnuptial agreement that will withstand legal scrutiny requires careful attention to both the substance of the agreement and the process by which it is created.

The quality of independent legal advice is one of the most important factors.

Each party’s lawyer must provide genuine, substantive advice about the agreement’s effect on their client’s rights.

Generic or template advice is not sufficient.

The lawyer must explain what the client would be entitled to under the Family Law Act without the agreement, how the agreement changes those entitlements, and both the advantages and disadvantages of entering into the agreement.

Courts have set aside agreements where the legal advice provided was found to be inadequate or superficial, so choosing a lawyer with real experience in binding financial agreements is important.

Full financial disclosure cannot be overstated.

Both parties must provide complete and honest information about their financial circumstances.

This includes all assets (even those held in trusts, companies, or overseas), all liabilities, all sources of income, and all financial resources.

Incomplete or inaccurate disclosure is one of the most common grounds for challenging a financial agreement, and it can undo years of careful planning.

The agreement should be fair and reasonable, even though there is no strict legal requirement for a postnuptial agreement to be “fair” in the same way that court orders must be.

An agreement that is heavily one-sided or that leaves one party in a significantly worse position may attract greater scrutiny from a court and may be more vulnerable to being set aside on the grounds of unconscionable conduct.

Agreements that reflect a genuine negotiation between both parties and provide reasonable outcomes for each tend to be more robust and less likely to be successfully challenged.

Timing and voluntary participation matter.

Both parties should have adequate time to review the agreement, seek legal advice, and consider the terms before signing.

Rushing the process, presenting the agreement as a take-it-or-leave-it proposition, or using emotional pressure to secure a signature are all red flags that could lead a court to set the agreement aside.

The process should feel collaborative, not coercive.

How Much Does a Postnuptial Agreement Cost in Australia?

The cost of a postnuptial agreement in Australia varies depending on the complexity of the couple’s financial situation and the law firm they choose to work with.

Traditional law firms often charge on an hourly basis, which can make the total cost unpredictable and lead to bill shock.

For straightforward agreements, costs might range from $2,500 to $5,000 per party, but for more complex situations involving business interests, trusts, or significant asset pools, costs can escalate well beyond that.

One of the barriers that prevents many Australian couples from putting a postnuptial agreement in place is this uncertainty around cost.

When a law firm cannot tell you upfront what the total fee will be, it is natural to hesitate.

The fear of receiving an unexpectedly large bill can outweigh the perceived benefit of the agreement, leaving many couples unprotected.

Fixed-fee binding financial agreements offer a solution to this problem.

By knowing exactly what the cost will be from the outset, couples can make an informed decision about whether to proceed without worrying about the bill growing beyond their budget.

This transparency also removes one of the common sources of stress in the legal process, allowing both parties to focus on the substance of the agreement rather than watching the clock.

It is important to remember that both parties must receive independent legal advice for the agreement to be valid, which means each person will incur their own legal costs.

However, even with this requirement, the total cost of a well-drafted postnuptial agreement is typically a fraction of what contested court proceedings would cost if the couple were to separate without one.

Court proceedings can easily run into tens of thousands of dollars, take months or years to resolve, and cause significant emotional harm to both parties and any children involved.

Need Help with a Postnuptial Agreement?

A postnuptial agreement gives married couples in Australia a practical way to protect their assets, clarify financial responsibilities, and avoid the cost and stress of court proceedings if their marriage were to break down.

Whether you have received an inheritance, started a business, entered a blended family, or simply want the peace of mind that comes with having clear financial arrangements in place, a postnuptial agreement can provide the certainty you need.

As binding financial agreement lawyers in Australia, my law firm can help you create a postnuptial agreement that is tailored to your circumstances and compliant with the Family Law Act 1975.

Contact us today by calling 1300 529 888.

Frequently Asked Questions

Can You Get a Postnuptial Agreement After You Are Already Married in Australia?

Yes, you can enter into a postnuptial agreement at any point during your marriage under section 90C of the Family Law Act 1975. The agreement must be in writing, signed by both parties, and each party must receive independent legal advice before signing. There is no deadline for creating one, and it can be done whether the marriage is going well or has broken down.

How Is a Postnuptial Agreement Different from a Prenuptial Agreement?

The only difference is timing. A prenuptial agreement is made before marriage under section 90B, while a postnuptial agreement is made during the marriage under section 90C. Both are types of binding financial agreements under the Family Law Act 1975 and must meet the same legal requirements to be enforceable, covering property division, superannuation, and spousal maintenance.

Can a Postnuptial Agreement Be Changed After It Is Signed?

Yes, a postnuptial agreement can be varied or replaced at any time, provided both parties agree and the new agreement meets all legal requirements under the Family Law Act. Each party must again receive independent legal advice on the new terms. Couples commonly update their agreements after significant life changes such as the birth of children or major financial shifts.

What Happens If You Separate Without a Postnuptial Agreement?

Without a postnuptial agreement, property division and spousal maintenance will be determined by the Family Court under Part VIII of the Family Law Act. The court assesses contributions made by each party, future needs, and what is just and equitable. This process can be lengthy, expensive, and emotionally draining, with the outcome decided by a judge rather than the couple.

Does a Postnuptial Agreement Cover Superannuation?

Yes, a postnuptial agreement can include provisions about how superannuation interests will be treated in the event of separation. The agreement can specify whether each party retains their own super, outline a splitting arrangement, or establish a formula for division. Because superannuation splitting must comply with both family law and superannuation legislation, proper legal drafting is essential.

Do Both Parties Need Separate Lawyers for a Postnuptial Agreement?

Yes, each party must obtain independent legal advice from their own separate lawyer before signing. The same lawyer cannot act for both spouses. Each lawyer must sign a statement confirming they provided advice about the effect of the agreement, its advantages, and its disadvantages. Without these signed statements, the agreement will not be legally binding.

Can a Postnuptial Agreement Protect an Inheritance?

Yes, protecting an inheritance is one of the most common reasons couples create postnuptial agreements in Australia. The agreement can specify that inherited assets remain the property of the receiving spouse and are excluded from the property pool if the marriage breaks down. Without a postnuptial agreement, an inheritance could be considered part of the shared assets available for division.

Does a Postnuptial Agreement Override a Will?

A postnuptial agreement and a will serve different legal purposes, and one does not automatically override the other. A BFA can include provisions about how certain assets will be treated upon the death of a party. It is important to ensure your postnuptial agreement and your will are consistent to avoid conflicting instructions about asset distribution.