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 Washington State, which is a community property state, spouses have the ability to enter into agreements to convert separate property into community property, commonly known as transmutation agreements. These agreements must be in writing and meet certain legal requirements to be valid. Washington law, specifically under RCW 26.16.010 and following sections, allows spouses to alter the character of their property from separate to community through a community property agreement or other written agreement that satisfies legal formalities. Similarly, debts can also be transmuted from separate to community or vice versa. However, it's important to note that changing the character of a debt from community to separate does not necessarily release the community or the other spouse from liability unless the creditor agrees in writing to look only to the separate estate of one spouse for satisfaction of the debt. This means that while spouses can agree between themselves to change the nature of a debt, such an agreement does not affect the rights of creditors unless the creditor consents to the change.