Prenuptial and postnuptial agreements are written agreements with the legal weight of a contract. These agreements dictate what will happen with your money, property, and debt if you and your spouse divorce. In other words, you are a making an agreement about who gets what if the marriage does not work out. Under Florida law, the main difference between a prenuptial agreement and a postnuptial agreement is timing. Prenuptial agreements are written and signed before the marriage, while postnuptial agreements are signed during the marriage. Because you and your fiancé or spouse are agreeing voluntarily after full financial disclosure, prenuptial and postnuptial agreements usually cannot be changed in the future.