You may be exempt from sales tax if you meet the following criteria: (1) You have a valid California Seller’s Permit, (2) You have completed a California Resale Certificate, (3) You have submitted a Bill of Lading from a common carrier for shipment of your purchase for transport out of state or country, (4) You have a valid Mexican Merchant card with the appropriate category code, (5) You qualify for a partial farm exemption and have filled out a California completed Farm Exemption Form and provided it to WCA.