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 California, which is a community property state, spouses have the ability to change the character of their property from separate to community through a process known as transmutation. This is governed by the California Family Code, particularly sections 850-853. Transmutation agreements must be in writing and include an express declaration that is made, joined in, consented to, or accepted by the spouse whose interest in the property is adversely affected. Such agreements allow couples to reclassify the ownership of their assets and debts, but it's important to note that changing the nature of a debt from community to separate does not necessarily relieve the community estate from liability unless the creditor agrees in writing to look only to the separate estate of one spouse for repayment. It's also crucial for spouses to understand that transmutation can have significant consequences on property rights, especially in the event of divorce or death, and therefore it is often recommended to consult with an attorney before entering into such an agreement.