(1) Except as provided in section 63-3033, Idaho Code:
(a)  Returns made on the basis of the calendar year shall be filed in the office of the Idaho state tax commission on or before the fifteenth day of April following the close of the calendar year and returns made on the basis of a fiscal year shall be filed in the office of the Idaho state tax commission on or before the fifteenth day of the fourth month following the close of the fiscal year.
(b)  In the case of a return for any period of less than one (1) year, the return shall be filed on or before the date required in this section, or on or before such date as required for such tax period by the Internal Revenue Code, whichever is later.
(2)  Returns made by farmer’s cooperatives to the extent the cooperative is taxable under section 63-3025B, Idaho Code, shall be due on or before September 15 following the close of the calendar year or on or before the fifteenth day of the ninth month following the close of the fiscal year. The provisions of section 63-3033, Idaho Code, shall not apply to returns due under this subsection.