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 Delaware, which is not a community property state but an equitable distribution state, marital property is not automatically considered to be owned jointly by both spouses. Instead, marital property is divided equitably upon divorce, not necessarily equally, based on various factors set by the court. A marital property partition agreement, known in Delaware 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 and fair disclosure of assets, and they must not be entered into under duress or undue influence. The agreement cannot be unconscionable and must be executed voluntarily by both parties with a clear understanding of the rights and obligations involved. If spouses cannot agree on the division of property, the Delaware courts will divide the property in an equitable manner, considering factors such as the length of the marriage, the age and health of the parties, and their respective contributions to the marriage. It is advisable for individuals considering a postnuptial agreement to consult with an attorney to ensure that the agreement is drafted correctly and meets all legal requirements.