(A) Returns of taxpayers, except as otherwise provided, must be filed on or before the fifteenth day of the fourth month following the taxable year.

(B)(1) Returns of "S" corporations and partnerships must be filed on or before the fifteenth day of the third month following the taxable year.

(2) Returns for foreign corporations that do not maintain an office or place of business in the United States must be filed on or before the fifteenth day of the sixth month following the taxable year.

(C) Returns of organizations exempt under Internal Revenue Code Section 501 reporting unrelated business income pursuant to § 12-6-4910(8), must be filed on or before the fifteenth day of the fifth month following the taxable year.

(D) Information returns provided in § 12-6-4950 must be filed on or before March 15 of each year.

(E) Returns filed electronically have the same due dates as provided in this section.