Cal. Rev. & Tax. Code § 60361

(a) The board shall forthwith ascertain as best it may the amount of the diesel fuel removed, entered, sold, delivered, or used and shall determine immediately the tax on that amount, adding to the tax a penalty of 25 percent of the amount of tax or five hundred dollars ($500), whichever is greater, and shall give the unlicensed person notice of this determination as prescribed by Section 60340. However, where the board determines that the failure to secure a license was due to reasonable cause, the penalty may be waived. Sections 60331 and 60332 shall be applicable with respect to the finality of the determination and the right of the unlicensed person to petition for a redetermination.
Any person seeking to be relieved of the penalty shall file with the board a statement under penalty of perjury setting forth the facts upon which he or she bases the claim for relief.
(b) In any case where the board does not determine an amount of tax due, the unlicensed person shall be subject to a penalty of one hundred dollars ($100), which penalty shall be immediately due and payable. Each subsequent violation shall increase the penalty amount by one hundred dollars ($100), up to a maximum penalty of five hundred dollars ($500). The board shall serve the person with a notice of penalty assessment in the manner prescribed by Section 60340 for service of notice of a deficiency determination. However, if the board finds that the failure of the person to secure a license was due to reasonable cause, the board may waive the penalty. A person seeking to be relieved of the penalty shall file with the board a statement under penalty of perjury setting forth the facts upon which the request for relief is based.