Purpose of chapter.

(a) It is the purpose of this chapter to impose:

(1) An income tax upon the entire net income of every resident and every resident estate and trust; and

(2) A franchise tax upon every corporation, financial institution, and unincorporated business for the privilege of carrying on or engaging in any trade or business within the District and of receiving such other income as is derived from sources within the District; provided, however, that, in the case of any corporation, the amount received as dividends from a corporation which is subject to taxation under this chapter or under Chapter 26 of this title , and, in the case of a corporation not engaged in carrying on any trade or business within the District, interest received by it from a corporation which is subject to taxation under this chapter or under Chapter 26 of this title shall not be considered as income from sources within the District for purposes of this chapter; and in the case of any corporation organized as a bank holding company under the provisions of the Bank Holding Company Act of 1956 and the Bank Holding Company Act Amendments of 1970, the amount received as dividends from a corporation which is subject to taxation under this chapter or under the provisions of § 47-2501 , and in the case of any such bank holding company not engaged in carrying on any trade or business within the District, interest received by it from a corporation which is subject to taxation under such sections, shall not be considered as income from sources within the District for purposes of this chapter. Provided further, that income derived from the sale of tangible personal property by a corporation, financial institution, or unincorporated business not carrying on or engaging in trade or business within the District as defined in §§ 47-1801.01 to 47-1801.04 shall not be considered as income from sources within the District for purposes of this chapter, with the exception of income from sale to the United States not excluded from gross income as provided in § 47-1803.02(a)(2)(I) ; provided, further, that dividends received from subsidiary corporations for whom the taxpayer provides services are deemed to be business income subject to apportionment.