If any user fails to make a return, the board shall make an estimate of the amount of fuel used by the user which is subject to the tax. The estimate shall be made for the month or months in respect to which the user failed to make a return and shall be based upon any information available to the board. Upon the basis of this estimate the board shall compute and determine the amount required to be paid to the State, adding to the sum thus fixed a penalty equal to 10 percent thereof. One or more determinations may be made for one or for more than one month.

In making a determination the board may offset overpayments for a month or months against underpayments for another month or months and against interest and penalties on the underpayments.

The amount of the determination, exclusive of penalties, shall bear interest at the modified adjusted rate per month, or fraction thereof, established pursuant to Section 6591.5, from the last day of the calendar month following the reporting period for which the amount, or any portion thereof, should have been reported until the date of payment.

If the failure of a user to file a return is due to fraud or an intent to evade the tax, a penalty of 25 percent of the amount required to be paid by the user, exclusive of penalties, shall be added thereto in addition to the 10-percent penalty provided in Section 8801.

Promptly after making its determination the department shall give to the user written notice of its estimate and determination, the notice to be served in the manner prescribed for service of notice of a deficiency determination.