A marital property partition agreement—also known as a partition and exchange agreement, a postmarital agreement, or a postnuptial agreement—is an agreement between spouses during marriage to convert marital property (also known as community property in some states) to one spouse’s separate property.

Property that is jointly owned by spouses or domestic partners (often owned as joint tenants with a right of survivorship) may also be partitioned or divided in a lawsuit or court action rather than by agreement of the spouses.

Laws regarding marital property partition agreements vary from state to state and are generally located in a state’s statutes—often in the family code or domestic relations code.

In Wisconsin, which is a community property state, marital property partition agreements, also known as postnuptial agreements, are recognized and enforceable. These agreements allow married spouses to alter the legal status of their property from marital to separate property. Under Wisconsin Statutes, specifically Chapter 766 concerning marital property, spouses have the right to enter into such agreements. The agreements must be in writing and signed by both parties to be valid. It is important for the agreement to be fair and for both spouses to fully disclose their assets; otherwise, the agreement may be subject to challenge in court. Additionally, while spouses can agree to partition or exchange property during the marriage, the division of property upon divorce is ultimately subject to the court's approval to ensure an equitable distribution. If spouses cannot agree on the division of property, a court may partition jointly owned property in a legal action. It is advisable for spouses considering a marital property partition agreement to consult with an attorney to ensure that the agreement complies with Wisconsin law and adequately protects their interests.