California Code, Government Code - GOV § 53997

(a) A local agency's obligation of contract, with regard to a financial transaction, shall commence when the legislative body adopts a resolution formally adopting, approving, or entering into any financial transaction, or when the treasurer, acting on his or her authority, enters into any financial transaction.

(b) Notwithstanding subdivision (a), the legislative body or the treasurer may commence its obligation of contract, with regard to a financial transaction, at any other point in the financial transaction with the mutual consent of the legislative body or the treasurer and the other party or parties to the financial transaction.