Cal. Rev. & Tax. Code § 19051

Any amount of tax in excess of that disclosed by the return, due to a mathematical error, notice of which has been mailed to the taxpayer, is not a deficiency assessment. The taxpayer has no right of protest or appeal based on that notice; however, the amount of tax erroneously omitted in the return may be assessed and collected in the manner provided in this part as in the case of deficiency assessments.