Cal. Rev. & Tax. Code § 12432

Except for a notice given pursuant to Section 12430 or 12431, or in the case of fraud or the failure to file a return, every notice of a deficiency assessment shall be given within four years after April 1st of the year following the year for which the amount of tax is assessed or within four years after the return is filed, whichever period expires the later. In the case of failure to file a return the notice shall be given within eight years after April 1st of the year following the year for which the amount of tax is assessed.