Cal. Civ. Code § 955
A transfer other than one intended to create a security interest (paragraph (1) or (3) of subdivision (a) of Section 9109 of the Commercial Code) of a nonnegotiable instrument which is otherwise negotiable within Division 3 of the Commercial Code but which is not payable to order or to bearer and a sale of accounts, chattel paper, payment intangibles, or promissory notes as part of a sale of the business out of which they arose (paragraph (4) of subdivision (d) of Section 9109 of the Commercial Code) shall be deemed perfected against third persons when such property rights have been endorsed or assigned in writing and in the case of such instruments or chattel paper delivered to the transferee, whether or not notice of such transfer or sale has been given to the obligor; but such endorsement, assignment, or delivery is not, of itself, notice to the obligor so as to invalidate any payments made by the obligor to the transferor.
Ca. Civ. Code § 955