In general, courts may strike down all or part of a prenuptial agreement. To be upheld, an agreement must be substantively and procedurally fair at the time of execution and it means it must be substantively fair at the time of execution. Procedural fairness refers to the manner of execution. For example both parties must make "full and complete financial disclosure," and both parties should have an opportunity to consult with a lawyer.

Substantive fairness means that the provisions of the agreement are fair to each party. Over time, an agreement executed when a couple is young and just starting may seem fair, but as the years go by, it becomes unfair to one party. For example, the wealthy middle age man who marries a much less affluent younger woman may sign an agreement that seems fair if the marriage fails a year or so later. However, such an agreement would be harder to enforce if the young woman invested many years caring for her elderly husband, or if she made contributions that advanced the couple’s financial situation.