Sticking to a shortlist of prenup guidelines strengthens your case. Here are six ground rules:
1. Both spouses need to fully understand what they're entering when signing a prenup.
"They need to have provided all kinds of financial records," Gilden said. "And they should be represented by attorneys. You can't be open enough about the process."
2. Prenups should be negotiated before planning the wedding.
"Once you plan the wedding, you want to have fun," Nachshin said. One common mistake is signing the prenup the day of the wedding, he said, which is what sports star Barry Bonds did, which led to a case that ultimately had to be settled by the California Supreme Court.
3. Delaying getting a prenup means you'll have to opt for a postnup after your wedding.
This move gives you less leverage with your spouse, since he or she has fewer incentives to sign a postnup, Gilden said. And if your future spouse won't sign a prenup, walk away, he advised.
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4. Postnups are still better than nothing.
If the postnup is carefully negotiated and there is full disclosure, the court will probably uphold it against challenges. Courts are upholding postnups more frequently now than they used to uphold them, Nachshin said.
5. After you're married, be careful not to commingle all assets.
The reason: The source of funds, such as joint or separate accounts, used to buy something determines its ownership. "Property ownership in a second marriage should be consistent with the prenup," Nachshin said. "And assets like cash and stocks shouldn't be commingled."
6. Appoint an arbiter to make decisions about gray areas, such as possessions.
John Olivieri, a partner at White and Case in New York City, said an arbiter can serve as the final line of defense to make sure your kids are protected and help avoid conflicts. "The more communication, the less misunderstanding," Olivieri said. He also advocates holding family meetings about inheritance intentions.
Following these guidelines can help avoid costly court battles.