Returns of cooperative associations

an exempt cooperative association described in section 1381(a)(1), or

an organization described in section 1381(a)(2) which is under an obligation to pay patronage dividends (as defined in section 1388(a)) in an amount equal to at least 50 percent of its net earnings from business done with or for its patrons, or which paid patronage dividends in such an amount out of the net earnings from business done with or for patrons during the most recent taxable year for which it had such net earnings,

a return made on the basis of a calendar year shall be filed on or before the 15th day of September following the close of the calendar year, and a return made on the basis of a fiscal year shall be filed on or before the 15th day of the 9th month following the close of the fiscal year.