26 CFR § 1.6073-2 - Fiscal years.
(a) Individuals other than farmers or fishermen. In the case of an individual on the fiscal year basis, the declaration must be filed on or before the 15th day of the 4th month of the taxable year. If, however, the requirements of section 6015(a) are first met after the 1st day of the 4th month and before the 2d day of the 6th month, the declaration must be filed on or before the 15th day of the 6th month of the taxable year. If such requirements are first met after the 1st day of the 6th month, and before the 2d day of the 9th month, the declaration must be filed on or before the 15th day of the 9th month of the taxable year. If such requirements are first met after the 1st day of the 9th month, the declaration must be filed on or before the 15th day of the 1st month of the succeeding fiscal year. Thus, if an individual taxpayer has a fiscal year ending on June 30, 1956, his declaration must be filed on or before October 15, 1955, if the requirements of section 6015(a) are met on or before October 1, 1955. If, however, such requirements are not met until after October 1, 1955, and before December 2, 1955, the declaration need not be filed until December 15, 1955.
(b) Farmers or fishermen. In the case of an individual on a fiscal year basis:
(1) If at least two-thirds of the individual's total estimated gross income from all sources for the fiscal year is from farming or fishing (including oyster farming), or
(2) If at least two-thirds of the individual's total gross income from all sources shown on the return for the preceding taxable year was from farming or fishing (including oyster farming) (with respect to declarations of estimated tax for taxable years beginning after November 10, 1978),
(c) Nonresident aliens. Notwithstanding the provisions of paragraph (a) of this section, in the case of a nonresident alien described in section 6072(c) (relating to returns of nonresident aliens whose wages are not subject to withholding) whose anticipated income for the fiscal year meets the requirements of section 6015(a), § 1.6015(a)–1, and § 1.6015(i)–1, the declaration of estimated tax for the fiscal year need not be filed before the 15th day of the 6th month of such fiscal year.