If parties have a prenup in place during estate planning, make it clear which document takes precedence. To avoid costly litigation in the future, the parties can resolve any disagreement with the prenup by using appropriate language to clarify which document takes precedence. When it isn't clear which document takes precedence and the terms of a prenuptial agreement conflict with a last will and testament, a probate court carefully examines the terms of the prenuptial agreement. The court is likely to find that the terms of the prenuptial agreement take precedence over the terms of a last will and testament. A prenup should indicate which law the reader should use to interpret it. If the prenuptial agreement does not contain this information, and a spouse dies in a state other than the state where the couple created the document, the laws in the state of the spouse's death take control. A prenup sometimes contains a “sunset” clause, which sets an expiration date for the agreement. After that date, a will automatically takes precedence. If the beneficiaries of the last will and testament can show that the prenuptial agreement is invalid, the court will not enforce its terms. This might occur if a spouse entered into a prenup under duress.