California Code, Food and Agricultural Code (Formerly Agricultural Code) - FAC § 21702

No person shall buy, sell, or accept any animal, unless the seller or donor gives, and the buyer or donee receives, at the time of the delivery of the animal, a written bill of sale or written instrument from the owner, or his or her agent, that gives the number, kind, breed, and sex, and, if branded, the brand and location of the brand on each animal.