California Code, Revenue and Taxation Code - RTC § 19059

(a) If a taxpayer is required by subdivision (a) of Section 18622 to report a change or correction by the Commissioner of Internal Revenue or other officer of the United States or other competent authority and does report the change or correction within six months after the final federal determination, or the Internal Revenue Service reports that change or correction within six months after the final federal determination, a notice of proposed deficiency assessment resulting from those adjustments may be mailed to the taxpayer within two years from the date when the notice is filed with the Franchise Tax Board by the taxpayer or the Internal Revenue Service, or within the periods provided in Section 19057, 19058, or 19065, whichever period expires later.

(b) If a taxpayer is required by subdivision (b) of Section 18622 to file an amended return and does file the return within six months of filing an amended return with the Commissioner of Internal Revenue, a notice of proposed deficiency assessment in excess of the self-assessed tax on the amended return, and resulting from the adjustments may be mailed to the taxpayer within two years from the date when the amended return is filed with the Franchise Tax Board by the taxpayer, or within the periods provided in Section 19057, 19058, or 19065, whichever period expires later.