Cal. Rev. & Tax. Code § 8732
A vendor of fuel the use of which is taxable under this part, who sells and delivers such fuel into a fuel tank shall, at the time of sale, collect the tax from the user and give to the user a receipt therefor in the manner and form prescribed by the board.
When fuel is sold through a keylock mechanism or other unattended mechanism it shall be presumed that the vendor delivered the fuel into the fuel tank of a motor vehicle and the vendor must collect the tax from the user. This presumption shall be rebutted and the vendor shall not collect the tax if the user certifies in writing to the vendor that all fuel delivered to him through a specific keylock mechanism or other unattended mechanism will be delivered into bulk containers.
Vendors of fuel required by this section to collect tax from users shall not be required to make such collections on sales and deliveries to users who are authorized by the board, as hereinafter provided, to purchase fuel without payment of tax to a vendor.
The board may issue written authorization to a holder of a valid use fuel permit to purchase fuel from a vendor designated by the user without payment of the tax to the vendor when the board finds (1) that the user consistently is using the fuel in vehicles which are operated partly without this state or off the highways of this state, or the user qualifies for the exemption provided in Section 8655, and (2) that to require collection of the tax from the user by the vendor would cause consistently recurring overpayments of the tax, and (3) that the revenue of the state with respect to the tax liability of such user is adequately secured. Such authorization may be revoked when any such condition no longer obtains.
Ca. Rev. and Tax. Code § 8732