California Code, Revenue and Taxation Code - RTC § 17651

(a) There is hereby imposed for each taxable year on the unrelated business taxable income (as defined in Section 23732) of every trust a tax computed as provided in subdivision (e) of Section 17041.  In making that computation for purposes of this section, the term “taxable income” as used in subdivisions (a) and (e) of Section 17041 shall be read as “unrelated business taxable income” as defined in Section 23732.

(b) The tax imposed by subdivision (a) shall apply in the case of any trust which is exempt, except as provided in this article, from taxation under this part by reason of Section 17631 and which, if it were not for such exemption, would be subject to Chapter 9 (commencing with Section 17731) relating to estates, trusts, beneficiaries, and decedents.