Under the law of some community property states, married persons may agree to convert some or all of their separate property to community property. Such an agreement may be referred to as an agreement to convert separate property to community property or as a transmutation agreement.

The legal character or nature of debts of married persons may also be changed by transmutation in some community property states—changing debts of the parties’ separate estates to debts of the community estate, or debts of the community estate to debts of the separate estates. But an agreement between married persons to change a community debt to the debt of one of the spouses separate estates may not be binding on the creditor—unless the creditor agrees in writing to only look to one spouse for satisfaction of the debt.

In community property states, the laws regarding the availability and scope of transmutation agreements vary from state to state. These laws are usually located in a state’s statutes—often in the family code or domestic relations code.

In New Mexico, which is a community property state, spouses have the ability to enter into agreements to convert their separate property into community property, commonly known as transmutation agreements. These agreements must be in writing and signed by both parties to be valid. New Mexico law, specifically under the New Mexico Statutes Annotated (NMSA) 40-3-8, allows for the transmutation of property from separate to community through such agreements. Similarly, debts can also be transmuted between separate and community estates. However, it's important to note that changing the nature of a community debt to that of a separate debt of one spouse may not be enforceable against a creditor unless the creditor consents in writing. Creditors are generally allowed to seek repayment from community property regardless of any agreement between spouses. The specifics of these agreements and their enforceability can be complex, and it is often advisable for spouses to consult with an attorney to ensure that their rights and intentions are properly reflected and legally sound.