Cal. Rev. & Tax. Code § 18036.5

In addition to the adjustments to basis provided by Section 1016(a) of the Internal Revenue Code, a proper adjustment shall also be made in the case of property the acquisition of which resulted under Section 18038.5 in the nonrecognition of any part of the gain realized on the sale of other property, to the extent provided in paragraph (4) of subdivision (b) of Section 18038.5.