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 Ohio, which is an equitable distribution state rather than a community property state, marital property is divided in a manner that is equitable but not necessarily equal in the event of a divorce. A marital property partition agreement, known in Ohio as a postnuptial agreement, is a contract between spouses that can be used to reclassify marital property as separate property of one spouse. These agreements must be in writing and signed by both parties. They are subject to certain legal requirements to be enforceable, such as full disclosure of assets and voluntary signing without coercion. Ohio courts will generally uphold a postnuptial agreement if it meets these requirements and is considered fair and not unconscionable at the time of enforcement. If spouses cannot agree on the division of property, a court may intervene and divide the property equitably. It's important to note that Ohio does not recognize common law marriage, so the statutes apply to legally married couples. Individuals considering a postnuptial agreement should consult with an attorney to ensure that the agreement complies with Ohio law and accurately reflects their intentions.