Cal. Rev. & Tax. Code § 41049

If an exemption is claimed by reason of the provisions of this part, and the service supplier or seller questions the validity of the claimed exemption, either the service supplier, seller, or the service user may request the department to issue a ruling as to the validity of the claimed exemption, accompanying the request with a statement showing the facts and basis for the claim. The department shall issue its ruling within 30 days of receipt of the request. Pending issuance of the ruling, the service supplier or seller shall not be obligated to collect the surcharge from the claimant.