New Mexico law provides no automatic property rights for unmarried cohabiting couples. Unlike married spouses, who acquire community property rights in assets accumulated during the marriage, unmarried partners own what they can prove they own. When a long-term relationship ends, whether by breakup or death, the absence of clear documentation about who owns what can lead to expensive disputes, uncertain outcomes, and outcomes that don't reflect the couple's actual intentions.
A cohabitation agreement is a contract between unmarried partners that establishes their financial rights and obligations toward each other. It creates legal clarity where the law provides none.
When a cohabitation agreement is especially important
Not every unmarried couple needs a formal cohabitation agreement, but several situations make one particularly valuable:
You own a home together or one partner contributed to the purchase of a home owned by the other. Without a written agreement, each partner's ownership interest in the property may be unclear, and a dispute could require litigation to resolve.
One partner left employment, reduced their working hours, or made career sacrifices to support the relationship or raise children. Without a written agreement, that partner may have difficulty establishing any claim to the economic value they contributed to the relationship.
You have been together long enough to accumulate significant shared assets, including furniture, vehicles, savings, or investments, and have an implicit understanding about ownership that has never been written down.
You have children together or one partner has children from a prior relationship, and you want clarity about financial obligations and how assets flow if the relationship ends.
One partner has significantly more assets than the other, and both partners want certainty about what happens to those assets during the relationship and at its end.
What a cohabitation agreement can cover
A cohabitation agreement can address a wide range of financial and property matters, including:
How property acquired before the relationship is classified and what happens to it during and after the relationship.
How property acquired during the relationship is owned, whether jointly or separately, and in what proportions if jointly.
How shared expenses, including housing costs, utilities, and household expenses, are divided.
What happens to specific assets, including the shared home, vehicles, and significant personal property, if the relationship ends.
What financial obligations, if any, one partner has toward the other if the relationship ends, including whether any form of support is appropriate.
How disputes about the agreement will be resolved.
What a cohabitation agreement cannot do
A cohabitation agreement is a contract between the parties. It governs the relationship between them. It does not create inheritance rights that override New Mexico's intestate succession law. If one partner dies without a will, the cohabitation agreement does not give the surviving partner the right to inherit. A will or other estate planning documents are still necessary for that purpose.
A cohabitation agreement also cannot establish custody or child support obligations for children. Those matters are governed by New Mexico family law regardless of any private agreement between the parents.
Is a cohabitation agreement enforceable in New Mexico?
New Mexico courts generally enforce cohabitation agreements as contracts, provided the agreement meets the standard requirements for a valid contract and is not based solely on a promise of future sexual services. Courts treat cohabitation agreements that address property rights and financial obligations in a committed relationship as legitimate contracts between consenting adults.
To maximize enforceability, a cohabitation agreement should be in writing, signed by both parties, entered into voluntarily without coercion, supported by consideration, and drafted clearly enough that the parties' intentions are evident from the document itself. Working with an attorney to draft the agreement helps ensure it meets these requirements.
How a cohabitation agreement fits into a broader estate plan
A cohabitation agreement addresses what happens during the relationship and if the relationship ends during both partners' lifetimes. It does not replace a will, a trust, or beneficiary designations, which address what happens at death. A complete plan for an unmarried couple typically includes both: a cohabitation agreement for the lifetime property and financial relationship and estate planning documents for the transition at death.
At Genus Law Group, we help unmarried couples in Albuquerque, Las Cruces, and throughout New Mexico put both pieces in place. We handle family law and estate planning together, which means we can draft a cohabitation agreement and an estate plan in a coordinated engagement that addresses both the lifetime and the death planning in a single process.
