For purposes of this subchapter, the term:
(1) “Taxable income” means the amount of net income derived from sources within the District, within the meaning of §§ 47-1810.01 to 47-1810.03, in excess of the exemption granted under § 47-1808.04; provided, that taxable income shall not include the gross income of a qualified community development entity, as defined in section 45D(c)(1) of the Internal Revenue Code of 1986, that has received an allocation or suballocation of new markets tax credits pursuant to section 45D(f) of the Internal Revenue Code of 1986, but only to the extent that the gross income is derived from one or more qualified low-income community investments, as defined in section 45D(d)(1) of the Internal Revenue Code of 1986.
(2) “Taxable period” means a taxable year, or a portion of a taxable year.