California Code, Revenue and Taxation Code - RTC § 8651.9

(2)(A) Neither the tax imposed by this section nor the tax imposed by Section 8651 shall apply to the use of dimethyl ether used in a vehicle during any period of time for which the owner or operator of the vehicle has paid the annual flat rate fuel tax as provided in Section 8651.7.

(B) To the extent that an owner or operator has provided written representation to a fuel seller that the owner or operator has prepaid the annual flat rate fuel tax as provided in Section 8651.7, the owner or operator shall be solely responsible for the taxes due under this part and the fuel seller shall not be liable for collecting and remitting those taxes.