When couples enter into a prenuptial agreement, one of the most common questions they ask is: how long does it actually last? In Australia, a prenup (formally known as a binding financial agreement) does not come with a built-in end date. In theory, it can remain in force for the entire duration of a relationship. In practice, though, a number of factors can erode its effectiveness or bring it to an end entirely.
There is no automatic expiry date
Under the Family Law Act 1975 (Cth), a binding financial agreement does not expire after a set number of years. Once signed correctly, with both parties having received independent legal advice, the agreement continues to apply until it is set aside, terminated, or replaced. This means a prenup signed before a wedding can still be relevant decades later if a couple separates. Whether it holds up, however, depends on how it was drafted and what has happened since.
Events that can effectively end a prenup
Even though a prenup does not have a legal expiry date, certain life events can render it unenforceable or cause a court to set it aside. The most significant of these include:
- The birth of children. If the agreement was made before children entered the picture and makes no provision for their welfare, a court may find that enforcing it would cause hardship to a child or their carer. Courts take child welfare seriously, and an agreement that ignores it entirely is vulnerable.
- A dramatic change in financial circumstances. If one partner becomes seriously ill, loses their capacity to earn, or accumulates significant debt that the agreement did not contemplate, a court may determine that enforcing the agreement would produce an unjust outcome.
- Fraud or unconscionable conduct. If either party can show the agreement was entered into under duress, as a result of misrepresentation, or that one party took advantage of the other's vulnerability, the agreement may be set aside regardless of how long it has been in place.
- Termination by mutual agreement. Both parties can agree to terminate the agreement at any time by signing a termination agreement, also known as a termination of financial agreement. Once this is executed correctly, the prenup ceases to have effect.
- A new binding financial agreement. If a couple signs a fresh agreement after marriage, it can supersede the earlier one. This is sometimes done deliberately when the original agreement no longer reflects the couple's circumstances.
Why poor drafting shortens a prenup's effective life
A prenup is only as durable as its drafting. Agreements that were prepared without proper legal advice, that contain ambiguous language, or that failed to disclose all relevant financial information at the time of signing are more likely to be challenged successfully in court. The longer a relationship continues, the more opportunity there is for changed circumstances to expose weaknesses in the original document. A skilled family lawyer will draft an agreement that anticipates future events, uses clear and unambiguous language, and complies strictly with the formal requirements of the Family Law Act.
It is also worth noting that the legal requirements for binding financial agreements have been interpreted strictly by Australian courts over the years. An agreement that seemed solid when signed may be found deficient if the legal landscape has shifted since then, or if the advice provided by one party's lawyer was inadequate at the time.
When to review or update your prenup
Given the factors above, it is sensible to review your prenup periodically rather than assuming it will hold indefinitely. Most family lawyers recommend revisiting the agreement whenever a significant life event occurs. These include:
- The birth or adoption of children
- A significant increase or decrease in either party's assets or debts
- Starting, buying, or selling a business
- Receiving a large inheritance or gift
- One party stopping work to care for children or an elderly relative
- Moving from a de facto relationship to a marriage (or vice versa)
Reviewing does not necessarily mean replacing. Sometimes a review will confirm that the original agreement remains appropriate. In other cases, a supplementary or replacement agreement will be necessary to properly reflect the couple's current situation.
De facto couples and timing
Binding financial agreements are available not just for married couples but also for those in de facto relationships. The timing considerations are slightly different in this context. A de facto couple can enter into an agreement before, during, or after their relationship, and the same general rules about duration and termination apply. If a de facto couple later marries, their existing agreement may or may not continue to cover the marriage, depending on how it was structured. This is an area where legal advice is essential, as an assumption that the old agreement still covers you could prove costly.
For more context on the rights that arise when a de facto relationship ends, understanding de facto break up entitlements in Australia can help clarify what is at stake if an agreement is not in place or is set aside.
The practical takeaway
A prenup in Australia can last for the lifetime of a relationship, but it is not a document you sign once and forget. Its durability depends on how it was drafted, whether it was properly executed, and whether the circumstances it was designed for still hold true. Treating a prenup as a living document, one that reflects your financial reality as your relationship evolves, gives it the best chance of doing its job when it matters most. If you are unsure whether your existing agreement is still fit for purpose, speaking with a family lawyer is the most straightforward way to find out.