California Code, Revenue and Taxation Code - RTC § 30173

If a distributor fails to make payment for stamps or meter register settings when payment is due, the board may compute and determine from any available records and information the amount required to be paid, including interest and penalties. One or more determinations may be made of the amount due for one or for more than one purchase. In making a determination the board may offset overpayments with respect to purchases of stamps or meter register settings against underpayments for purchases and interest and penalties on the underpayments. The board shall give the distributor written notice of its determination in the manner provided by Section 30206. Except in the case of fraud, every notice of a determination made under this article shall be given within three years of the due date for payment of the purchase of stamps or a meter register setting.