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 Michigan, which is not a community property state but an equitable distribution state, marital property is divided equitably in the event of a divorce, rather than equally. A marital property partition agreement, known in Michigan as a postnuptial agreement, is a legal tool that allows married spouses to designate certain marital assets as separate property. This agreement must be in writing and signed by both parties. It is important that the agreement is entered into voluntarily and without coercion, with full disclosure of assets by both parties, and that it is fair and not unconscionable. If a couple does not have a postnuptial agreement and they decide to divorce, the court will divide their marital property equitably, considering factors such as the length of the marriage, the contributions of each spouse, and the needs of each party. It is important to note that while postnuptial agreements are recognized in Michigan, they are scrutinized by courts to ensure fairness and compliance with legal standards. For specific advice and drafting of such agreements, it is recommended to consult with an attorney who specializes in family law.