interest means any capital or profits interest in a domestic partnership if— (i) such interest is acquired by the taxpayer after December 31, 2017, from the partnership solely in exchange for cash, (ii) as of the time such interest was acquired, such partnership was a qualified opportunity zone business (or, in the case of a new partnership, such partnership was being organized for purposes of being a qualified opportunity zone business), and (iii) during substantially all of the taxpayer’s holding period for such interest, such partnership qualified as a qualified opportunity zone business. (D) Qualified opportunity zone business property (i) In general The term qualified opportunity zone business property means tangible property used in a trade or business of the taxpayer if— (I) such property was acquired by the taxpayer by purchase (as defined in section 179(d)(2)) after December 31, 2017, (II) the original use of such property in the qualified opportunity zone commences with the taxpayer or the taxpayer substantially improves the property, and (III) during substantially all of the taxpayer’s holding period for such property, substantially all of the use of such property was in a qualified opportunity zone. (ii) Substantial improvement For purposes of subparagraph (A)(ii), property shall be treated as substantially improved by the taxpayer only if, during any 30-month period beginning after the date of acquisition of such property, additions to basis with respect to such property in the hands of the taxpayer exceed an amount equal to the adjusted basis of such property at the beginning of such 30-month period in the hands of the taxpayer. (iii) Related party For purposes of subparagraph (A)(i), the related person rule of section 179(d)(2) shall be applied pursuant to paragraph (8) of this subsection in lieu of the application of such rule in section 179(d)(2)(A). (3) Qualified opportunity zone business (A) In general The term qualified opportunity zone business means a trade or business— (i) in which