Cal. Rev. & Tax. Code § 38444

The board may decrease or increase the amount of the determination before it becomes final, but the amount may be increased only if a claim for the increase is asserted by the board at or before the hearing. Unless the penalty imposed by Section 38415 or Section 38424 applies to the amount of the determination as originally made or as increased, the claim for increase must be asserted within eight years after the last day of the calendar month following the quarterly period for which the increase is asserted.