Cal. Rev. & Tax. Code § 19907

Unless otherwise specifically provided, the terms “Internal Revenue Code,” “Internal Revenue Code of 1954,” or “Internal Revenue Code of 1986,” for purposes of this part, mean Title 26 of the United States Code, including all amendments thereto, as enacted on the specified date for the applicable taxable year as defined in paragraph (1) of subdivision (a) of Section 17024.5.