Tax on unincorporated businesses — Levy and rates.

(a) Except as exempted under subchapter II of this chapter , for the privilege of carrying on or engaging in any trade or business within the District and of receiving income from sources within the District, there is levied:

(1) For 1 taxable year beginning after December 31, 1974, a tax at the rate of 12% upon the taxable income of every unincorporated business, whether domestic or foreign;

(2) For the taxable years beginning after December 31, 1975, a tax at the rate of 9% upon the taxable income of every unincorporated business, whether domestic or foreign, except that, effective October 1, 1984, the rate of tax shall be 10% upon the taxable income for any taxable period, except that for taxable years beginning after December 31, 1994, the rate of tax shall be 9.5%;

(3) For the taxable years beginning after December 31, 2002, a tax at the rate of 9.5% upon the taxable income of every unincorporated business, whether domestic or foreign;

(3A)

(A) A surtax at the rate of 2.5% on the tax determined under paragraph (2) or (3) of this subsection, as applicable.

(B) Subparagraph (A) of this paragraph shall apply for any tax period beginning after September 30, 1992.

(3B)

(A) A surtax at the rate of 2.5%, separate from and in addition to, the surtax imposed by paragraph (3A) of this subsection, on the tax determined under paragraph (2) or (3) of this subsection, as applicable, for any tax period beginning after September 30, 1994.

(B) Subparagraph (A) of the paragraph shall apply for any tax period beginning after September 30, 1994.

(4) For the taxable years beginning after December 31, 2003, a tax at the rate of 9.975% upon the taxable income of every unincorporated business, whether domestic or foreign;

(5) For the taxable year beginning after December 31, 2014, a tax at the rate of 9.4% upon the taxable income of every unincorporated business, whether domestic or foreign; and

(6) Subject to availability of funding and in accordance with § 47-181 , upon the taxable income of every unincorporated business, whether domestic or foreign, a tax at the rate of 9%, 8.75%, 8.5%, or 8.25%.