Rev. & Tax. Code, § 23104

(a) For purposes of this part only, any corporation that is not incorporated under the laws of this state and whose sole activity in this state is engaging in convention and trade show activities, as described in Section 513(d)(3)(A) of the Internal Revenue Code, for seven or fewer calendar days, or any portion thereof, during the taxable year and that does not derive more than ten thousand dollars ($10,000) of gross income reportable to this state from those activities during that taxable year is not a corporation doing business in this state.

(b) For purposes of this section, the determination of gross income reportable to this state of a taxpayer shall be made by including the gross income reportable to this state of each member of the “commonly controlled group” (as defined by Section 25105) of which the taxpayer is a member.