Cal. Rev. & Tax. Code § 24917

Whenever it appears that the basis of property in the hands of the corporation is a substituted basis, then the adjustments provided in Section 24916 shall be made after first making in respect of that substituted basis proper adjustments of a similar nature in respect of the period during which the property was held by the transferor, donor, or grantor, or during which the other property was held by the person for whom the basis is to be determined. A similar rule shall be applied in the case of a series of substituted bases.