Cal. Rev. & Tax. Code § 32271

(a) If the board is dissatisfied with the return or returns filed or amount of tax paid to the state by any taxpayer, it may compute and determine the amount to be paid based upon any information available to it. One or more additional determinations may be made of the amount of tax due for one or for more than one period. The amount of tax so determined shall bear interest at the modified adjusted rate per month, or fraction thereof, established pursuant to Section 6591.5, from the 15th day after the close of the period for which the amount of the tax, or any portion thereof, should have been reported until the date of payment. In making a determination, the board may offset overpayment for a period or periods against underpayments for another period or periods and against the interest and penalties on the underpayments.
(b) If any part of the deficiency for which a determination of an additional amount due is made is found to have been occasioned by negligence or intentional disregard of this part or authorized rules, a penalty of 10 percent of the amount of the determination shall be added, plus interest as above provided.
(c) If any part of the deficiency for which a determination of an additional amount due is made is found to be occasioned by fraud or an intent to evade this part or authorized rules, a penalty of 25 percent of the amount of the determination shall be added, plus interest as above provided.
(d) The board shall give to the taxpayer written notice of its determination. The notice shall be served in one of the following manners:
1. (1) By placing the notice in a sealed envelope, with postage paid, addressed to the taxpayer at their address as it appears in the records of the board. Service made pursuant to this paragraph shall be deemed complete at the time of the deposit of the notice in the United States Post Office, or a mailbox, sub-post office, substation or mail chute or other facility regularly maintained or provided by the United States Postal Service without extension of time for any reason.
2. (2) By personally delivering the notice to the person to be served. Service made pursuant to this paragraph shall be deemed complete at the time of delivery. Personal service to a corporation may be made by delivery of a notice to any person designated in the Code of Civil Procedure to be served for the corporation with summons and complaint in a civil action.
3. (3)
  1. (A) By delivering the notice electronically via secure transmission when either of the following applies:
    1. (i) The taxpayer requests the notice of determination to be sent electronically via secure transmission.
    2. (ii) The board has evidence that the taxpayer no longer receives mail at the address of record and has previously provided an address for electronic mail.
  2. (B) Service provided pursuant to subparagraph (A) shall be deemed complete at the time the board electronically transmits the notice via the taxpayer’s secure web portal, without extension of time for any reason.