Cal. Rev. & Tax. Code § 6357.3

(a) On and after July 1, 2011, there are exempted from the taxes imposed by Sections 6051.8 and 6201.8, the gross receipts from the sale in this state of, and the storage, use, or other consumption in this state of both of the following:
1. (1) Diesel fuel purchased for use or used in a manner that is exempt from the tax imposed pursuant to Part 31 (commencing with Section 60001) of Division 2 and not subject to the backup tax imposed by Section 60058 or the payment requirement specified in Section 60108.
2. (2) Diesel fuel subject to the payment requirement specified in Section 60502.2.
(b) No exemption from the tax imposed pursuant to Sections 6051.8 and 6201.8 shall be allowed under this section unless the purchaser furnishes the seller with an exemption certificate, completed in accordance with any instructions or regulations as the board may prescribe.
(c) If a purchaser certifies in writing to the seller that the diesel fuel purchased without payment of the tax imposed pursuant to Section 6051.8 or 6201.8 will be used in a manner entitling the seller to regard the gross receipts or sales price from the sale as exempt from that tax, and uses the diesel fuel in a manner that subjects the diesel fuel to the tax imposed pursuant to Section 60050, the purchaser shall be liable for payment of the sales tax imposed pursuant to Section 6051.8, with applicable interest, as if the purchaser were a retailer making a retail sale of the diesel fuel at the time the fuel is so used, and the sales price of the diesel fuel to the purchaser shall be deemed the gross receipts from that retail sale.