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 Idaho, which is not a community property state but rather a common law property state, marital property is not automatically considered jointly owned by spouses. Instead, property acquired during the marriage is typically considered to belong to the spouse who purchased it unless it is placed in both names. However, spouses in Idaho can enter into a marital property partition agreement, also known as a postnuptial agreement, to change the ownership of marital property. Such agreements allow spouses to agree on how their property should be classified and divided, either during the marriage or in the event of a divorce. These agreements must be in writing and are subject to certain legal requirements to be enforceable, including full disclosure of assets and voluntary signing without coercion. If spouses cannot agree on the division of property, the courts in Idaho will divide property equitably, though not necessarily equally, in the event of a divorce. It is advisable for spouses considering a marital property partition agreement to consult with an attorney to ensure that the agreement complies with Idaho laws and fully protects their interests.