California Code, Revenue and Taxation Code - RTC § 60201.2

A supplier who sells taxable diesel fuel shall collect from the purchaser the diesel fuel tax imposed under Section 60050. At the election of the purchaser, the payment of the diesel fuel tax owed on every gallon of diesel fuel purchased from a supplier shall be remitted to the supplier on terms agreed upon between the purchaser and the supplier or on or before five working days before the last day of the calendar month following the monthly period to which it relates. This election shall be subject to a condition that the purchaser's remittances of all amounts of tax due to the seller shall be paid by electronic funds transfer. The purchaser's election may be terminated by the seller if the purchaser does not make timely payments to the seller as required by this section. This section shall not apply where the purchaser is required by a supplier to pay cash or cash equivalent for diesel fuel purchases.