Cal. Rev. & Tax. Code § 6363.2
There are exempted from the taxes imposed by this part, the gross receipts from the sale in this state of, and the storage, use, or other consumption in this state of, tangible personal property that is sold to a successful bidder at an auction that is conducted by, or affiliated with, a nonprofit organization, if the purpose of that auction is to obtain revenue for the funding of a shelter for homeless individuals and families and those revenues obtained are actually expended for that purpose. For purposes of this section, "nonprofit organization" means an organization that is exempt from taxation under Section 23701d. This section shall not apply to any sale at an auction that is conducted more than once during any 12-month period.
Ca. Rev. and Tax. Code § 6363.2