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 Iowa, which is not a community property state but rather an equitable distribution state, marital property is not automatically considered to be owned jointly by both spouses. Instead, during a divorce, marital property is divided equitably, but not necessarily equally, based on a set of factors the court considers. A marital property partition agreement, known in Iowa as a postnuptial agreement, allows 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 liabilities, and both parties must enter into the agreement voluntarily and without coercion. The agreement cannot be unconscionable and must not promote divorce. If spouses cannot agree on the division of property, the court will divide it for them during the divorce proceedings. It's important to note that while spouses can agree to partition or divide property, such agreements are subject to legal scrutiny and must comply with Iowa's legal standards for postnuptial agreements.