Cohabitation agreements (also known as nonmarital agreements) are similar to prenuptial agreements for couples who are planning to marry—but cohabitation agreements are for people who are living together and having a sexual relationship without being married. These agreements address issues that may arise during the relationship (payment of rent and other expenses, household chores)—and issues that may arise if the cohabitation relationship ends (ownership and division of home or other property, support).

In Idaho, cohabitation agreements, also known as nonmarital agreements, are recognized and enforceable. These agreements allow couples who live together without being married to outline their financial arrangements, property division, and other responsibilities during and after their relationship. While Idaho does not have specific statutes that govern cohabitation agreements, these contracts are generally upheld if they are in writing, entered into voluntarily by both parties, and if the terms do not violate public policy or law. It is important for individuals entering into such agreements to fully disclose their financial situations to each other and to have the agreement drafted by an attorney to ensure that it is legally sound and reflects their intentions. If the cohabitation relationship ends, the agreement serves as a guide for resolving issues such as the division of property and debt, and it may also address support, though there is no legal obligation for support between unmarried partners in Idaho as there is in a marriage.