(a) In general. Except as otherwise provided in § 1.512(a)-3, § 1.512(a)-4, or paragraph (f) of this section, section 512(a)(1) defines unrelated business taxable income as the gross income derived from any unrelated trade or business regularly carried on, less those deductions allowed by chapter 1 of the Code which are directly connected with the carrying on of such trade or business, subject to certain modifications referred to in § 1.512(b)-1. To be deductible in computing unrelated business taxable income, therefore, expenses, depreciation, and similar items not only must qualify as deductions allowed by chapter 1 of the Code, but also must be directly connected with the carrying on of unrelated trade or business. Except as provided in paragraph (d)(2) of this section, to be directly connected with the conduct of unrelated business for purposes of section 512, an item of deduction must have proximate and primary relationship to the carrying on of that business. In the case of an organization which derives gross income from the regular conduct of two or more unrelated business activities, unrelated business taxable income is the aggregate of gross income from all such unrelated business activities less the aggregate of the deductions allowed with respect to all such unrelated business activities. For the treatment of amounts of income or loss of common trust funds, see § 1.584-2(c)(3).