Cal. RTC § 6511

If any person fails to make a return, the board shall make an estimate of the amount of the gross receipts of the person, or, as the case may be, of the amount of the total sales price of tangible personal property sold or purchased by the person, the storage, use, or other consumption of which in this state is subject to the use tax. The estimate shall be made for the period or periods in respect to which the person failed to make a return and shall be based upon any information which is in the board’s possession or may come in its possession. Upon the basis of this estimate the board shall compute and determine the amount of tax or other amount required to be paid to the state, adding to the sum thus arrived at a penalty equal to 10 percent thereof. One or more determinations may be made for one or for more than one period. When a business is discontinued a determination may be made at any time thereafter, within the periods specified in Section 6487, as to liability arising out of that business, irrespective of whether the determination is issued prior to the due date of the liability as otherwise specified in this part.