California Code, Revenue and Taxation Code - RTC § 60301

If any person fails, neglects, or refuses to file the return within the time prescribed by this chapter, the board shall estimate the diesel fuel removals, entries, sales, deliveries, or use for the period for which he or she made no return within the time required. Upon the basis of this estimate, the board shall determine the tax due from the person, and shall add to the tax a penalty of 10 percent thereof. The board may make a determination for more than one period and may make one or more determinations for the same period.