Revenue and Taxation Code § 17737

(a) For purposes of computing the taxable income of the estate or trust and the taxable income of a spouse to whom Section 682(a) of the Internal Revenue Code, relating to income of an estate or trust in the case of divorce, etc., as it read on January 1, 2015, applies, that spouse shall be considered as the beneficiary for purposes of this chapter.

(b) Subdivision (a) shall not apply for any divorce or separation instrument executed after December 31, 2025, or for any divorce or separation instrument executed on or before December 31, 2025, and modified after that date, if the modification expressly provides that the amendments made by this subdivision apply to such modification.