Cal. RTC § 6481

If the board is not satisfied with the return or returns of the tax or the amount of tax, or other amount, required to be paid to the state by any person, it may compute and determine the amount required to be paid upon the basis of the facts contained in the return or returns or upon the basis of any information within its possession or that may come into its possession. One or more deficiency determinations may be made of the amount due 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.