RTC §60201.3: (a) A supplier is relieved from liability for diesel fuel tax insofar as the sales of the diesel fuel are represented by accounts which have been found worthless and charged off for income tax purpose

(a) A supplier is relieved from liability for diesel fuel tax insofar as the sales of the diesel fuel are represented by accounts which have been found worthless and charged off for income tax purposes. If the supplier has previously paid the amount of the tax, he or she may, under the rules and regulations prescribed by the board, take a credit in that amount. If those accounts are thereafter in whole or in part collected by the supplier, the gallons of diesel fuel represented by the amounts collected shall be included in the first return filed after that collection and the amount of the tax thereon shall be paid with the return. The board may, at its option, require the supplier to submit periodic reports listing accounts delinquent for a 90-day period or more. (b) Any customer of a supplier who has failed to pay for diesel fuel purchased and for which the supplier has been allowed a credit under subdivision (a) is liable to the state for the diesel fuel tax as an unlicensed supplier and the tax, applicable penalties, and interest become immediately due and payable under the unlicensed persons provisions contained in Article 6 (commencing with Section 60360) of Chapter 6. The notice of determination issued under Section 60361 shall be given to the customer within three years of the last day of the calendar month following the reporting period for which the supplier took a credit for the tax previously paid on the customer’s account or within three years after the date a refund of the tax was paid.