Stuart Fowler, a family law specialist at Stuart Fowler and Partners, says lawyers are seeing a bit of extra interest in these agreements since then, mainly from people entering second marriages or where one partner has vastly more assets than the other.

But didn't they always exist?

They did, but Michael Taussig, QC, says they were never legally binding. Under the Family Law Act, a judge could choose to override the agreement to come to a settlement that was fair and equitable. In NSW, de facto and same-sex couples had more certainty as they could enter into cohabitation agreements under State law. The latest changes have merely brought married couples into line with non-married couples.

Are there any rules about what the agreements can cover?

You've probably seen newspaper reports of agreements covering such areas as who does the washing and how often the couple has "marital relations". Don't pay too much attention to that. The intention of the legislation is to allow binding financial agreements, and Fowler says it's better to keep them to that. "While it is possible to include lifestyle clauses it is generally not thought to be a good idea," Fowler says. "If they are breached, the agreement may be able to be set aside."

What if I'm already married?

Fowler says agreements can be entered into by couples intending to marry, couples who are already married (though these become nuptial agreements), or couples who have broken up and want to agree on a split of assets rather than seeking court orders.

What do I have to do?

The first step is to find a good family lawyer - and one for your partner. Fowler says both parties are required to provide a "full and frank" disclosure, in writing, of their financial position - their assets and liabilities, income and outgoings, and "financial resources" such as superannuation. If you're the weaker party financially, Taussig says it may be a good idea to ask your partner to pay for an accountant to investigate his or her financial affairs.

Then, it's a matter of working out an agreement that is acceptable to you both.

Fowler says because most agreements are made between people of child-bearing age, it's important to make provisions for any children born or adopted - even if there are no plans for children. He says this is because agreements can be set aside if they cause undue hardship, such as might happen if one partner finds he or she has children to support.

"You also have to be realistic," Fowler says. "If the agreement is to last for some time, you have to contemplate that the law presently says your rights to claim percentages of assets varies according to the length of the marriage.

"The difficulty is that we don't yet know how the courts will approach the question of setting aside these agreements. [There's a view that] black-and-white contracts sit a little ill with the concepts of justice, fairness, equality of circumstances and so on which have been the basis of matrimonial law."

I don't want my agreement set aside. Is there any way I can make sure it isn't?

Fairness is a good start. Fowler says if an agreement is totally unjust and unreasonable it risks being set aside as unconscionable. Both parties should also enter into it willingly, not under duress. He says the legislation also requires both parties to obtain independent legal advice on the implications of the agreement for them. He says agreements can have review clauses built into them so they can be adapted as the couple's circumstances change.