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 Montana, marital property is not recognized as community property since Montana is an equitable distribution state, not a community property state. This means that during a divorce, marital property is divided equitably, but not necessarily equally, based on a variety of factors. A marital property partition agreement in Montana, also known as a postnuptial agreement, allows married spouses to agree on how their property should be classified as separate or marital, and how it should be divided in the event of a divorce. These agreements must be in writing and are subject to certain legal requirements to be enforceable, such as full disclosure of assets and fair dealing between the spouses. If spouses cannot agree on the division of property, a Montana court will divide the property for them during a divorce proceeding, taking into account factors such as the duration of the marriage, the economic circumstances of each spouse, and contributions to the marital estate. It's important for individuals considering a marital property partition agreement in Montana to consult with an attorney to ensure that the agreement is drafted correctly and meets all legal requirements.