FAM §721: (a) Subject to subdivision (b), either spouse may enter into any transaction with the other, or with any other person, respecting property, which either might if unmarried.

(a) Subject to subdivision (b), either spouse may enter into any transaction with the other, or with any other person, respecting property, which either might if unmarried. (b) Except as provided in Sections 143, 144, 146, 16040, 16047, and 21385 of the Probate Code, in transactions between themselves, spouses are subject to the general rules governing fiduciary relationships that control the actions of persons occupying confidential relations with each other. This confidential relationship imposes a duty of the highest good faith and fair dealing on each spouse, and neither shall take any unfair advantage of the other. This confidential relationship is a fiduciary relationship subject to the same rights and duties of nonmarital business partners, as provided in Sections 16403, 16404, and 16503 of the Corporations Code, including, but not limited to, the following: (1) Providing each spouse access at all times to any books kept regarding a transaction for the purposes of inspection and copying. (2) Rendering upon request, true and full information of all things affecting any transaction that concerns the community property. Nothing in this section is intended to impose a duty for either spouse to keep detailed books and records of community property transactions. (3) Accounting to the spouse, and holding as a trustee, any benefit or profit derived from any transaction by one spouse without the consent of the other spouse that concerns the community property.