Cal. Rev. & Tax. Code § 6010.40
"Sale" and "purchase," for the purpose of this part, do not include the transfer by a city, city and county, county, or other local government animal shelter or a nonprofit animal welfare organization of any animal to an individual for use as a pet, or any charges made by the government shelter or nonprofit organization for services in connection with the transfer of that animal, including, but not limited to, the spaying or neutering or future spaying or neutering of the animal, or any vaccination, future vaccination, or similar service. For purposes of this section, "nonprofit animal welfare organization" means any organization formed and operated for the primary purpose of prevention of abuse, neglect, or exploitation of animals and that qualifies for the exemption from taxation pursuant to Section 23701d.
Ca. Rev. and Tax. Code § 6010.40