CA Rev & Tax Code Section 8852.5

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 Unless the penalty imposed by Section 8780 or Section 8804 applies to the amount of the determination as originally made or as increased, the claim for increase must be asserted within eight years after the last day of the month following the month for which the return for the period for which the increase is asserted was due or within eight years after the return was filed, whichever period expires the later.