Cal. Rev. & Tax. Code § 38421

If any person fails to make a return, the board shall make an estimate of the amount of the total timber harvested by the person and the immediate harvest value of that timber. 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 into its possession. 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 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 person discontinues activities subject to the tax, a determination may be made at any time thereafter, within the periods specified in Section 38417, as to liability arising out of the person’s activities subject to the tax, irrespective of whether the determination is issued prior to the due date of the liability as otherwise specified in this part.