California Code, Revenue and Taxation Code - RTC § 25106.5

(a) The Franchise Tax Board may adopt regulations necessary to ensure that the tax liability or net income of any taxpayer whose income derived from or attributable to sources within this state which is required to be determined by a combined report pursuant to Section 25101 or 25110 of this chapter, and of each entity included in the combined report, both during and after the period of inclusion in the combined report is properly reported, determined, computed, assessed, collected, or adjusted.

(b) Notwithstanding subdivision (a), the Franchise Tax Board shall not adopt regulations under the authority of this section which shall in any manner determine, prescribe, or otherwise affect (1) the inclusion or exclusion in the combined report of those entities whose income and apportionment factors are to be taken into account pursuant to Sections 25101 and 25110 of this chapter, or (2) after the period of inclusion, cause the income or expenses of an entity which is excluded from a combined report pursuant to Sections 25101 and 25110 of this part to be included in a combined report.