In the case of returns under section 6012, 6013, 6017, or 6031 (relating to income tax under subtitle A), returns made on the basis of the calendar year shall be filed on or before the 15th day of April following the close of the calendar year and returns made on the basis of a fiscal year shall be filed on or before the 15th day of the fourth month following the close of the fiscal year, except as otherwise provided in the following subsections of this section.

Returns of corporations under section 6012 made on the basis of the calendar year shall be filed on or before the 15th day of March following the close of the calendar year, and such returns made on the basis of a fiscal year shall be filed on or before the 15th day of the third month following the close of the fiscal year. Returns required for a taxable year by section 6011 (e)(2) (relating to returns of a DISC) shall be filed on or before the fifteenth day of the ninth month following the close of the taxable year.

Returns made by nonresident alien individuals (other than those whose wages are subject to withholding under chapter 24) and foreign corporations (other than those having an office or place of business in the United States or a FSC or former FSC) under section 6012 on the basis of a calendar year shall be filed on or before the 15th day of June following the close of the calendar year and such returns made on the basis of a fiscal year shall be filed on or before the 15th day of the 6th month following the close of the fiscal year.

In the case of an income tax return of—

In the case of an income tax return of an organization exempt from taxation under section 501 (a) (other than an employees’ trust described in section 401 (a)), a return shall be filed on or before the 15th day of the 5th month following the close of the taxable year.