California Code, Revenue and Taxation Code - RTC § 19755

(a)(1) Notwithstanding Section 19057, and except as provided in paragraph (2), with respect to proposed deficiency assessments related to an abusive tax avoidance transaction, a notice of a proposed deficiency assessment may be mailed to the taxpayer within eight years after the return was filed, or within the period otherwise provided in Article 3 (commencing with Section 19031) of Chapter 4 of this part, whichever expires later.

(2) For notices mailed on or after August 1, 2011, with respect to proposed deficiency assessments related to an abusive tax avoidance transaction, a notice of a proposed deficiency assessment may be mailed to the taxpayer within 12 years after the return was filed, or within the period otherwise provided in Article 3 (commencing with Section 19031) of Chapter 4 of this part, whichever expires later.