RTC §6563: (a) 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 t

(a) 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 Unless the penalty imposed by Section 6485 or Section 6514 applies to the amount of the determination as originally made or as increased, the claim for increase must be asserted during one of the following applicable periods: (1) In the case of any taxpayer whose reported gross receipts and total sales price of property sold or purchased by him or her is less than ten million dollars ($10,000,000) in each calendar quarter of the period or periods to which the determination applies, within three years after the first deficiency determination or within three years after the time tax records requested by the board were made available, whichever is later. (2) In the case of any other taxpayer, within eight years after the first deficiency determination or within eight years after the time tax records requested by the board were made available, whichever is later. (b) If the taxpayer and the board mutually agree, the time limits specified in subdivision (a) may be waived. (c) The board shall specify the information on which it bases its increase.