Cal. Revenue and Taxation Code - RTC § 19755. Section 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.
(b)
This section shall apply to any return filed under this part on or after January 1, 2000. Paragraph (2) of subdivision (a) shall apply to taxable years that have not been closed by a statute of limitations, res judicata, or otherwise, as of August 1, 2011.