N.Y. Comp. Codes R. & Regs. Tit. 20 §§ 7-3.7
(Tax Law, section 213-b(g))
In the case of a short taxable year of a taxpayer for which a declaration of estimated tax is required to be made and filed, the estimated tax, after deducting the amount, if any, paid as a mandatory first installment for such period, must be paid in equal installments. One such installment must be paid at the time of filing the declaration, one on the 15th day of the ninth month of the current taxable year (unless the short taxable year closed prior to such ninth month, in which case the installment will be eliminated), and one on the 15th day of the last month of the current taxable year.
Corporation A has a short taxable year of 10 months, from January 1, 2021, to October 31, 2021. If there is a reasonable expectation before June 1, 2021, that Corporation A's estimated tax will exceed $1,000 for such short taxable year, the declaration is required to be made and filed on or before June 15, 2021. The estimated tax (after deducting the amount of mandatory first installment paid, if any) is payable in three equal installments: one on the date of filing the declaration and one each on September 15, 2021, and October 15, 2021.
If, instead, there is a reasonable expectation on or after June 1, 2021, but before September 1, 2021, that Corporation A's estimated tax will exceed $1,000, the declaration is required to be made and filed on or before September 15, 2021. The estimated tax (after deducting the amount of mandatory first installment paid, if any) is payable in two equal installments: one on the date of filing the declaration and one on October 15, 2021.
If there is a reasonable expectation on or after September 1, 2021, but not before such date, that Corporation A's estimated tax will exceed $1,000, the declaration is required to be made and filed on or before October 15, 2021. The estimated tax (after deducting the amount of mandatory first installment paid, if any) is payable in full on the date of filing the declaration.
N.Y. Comp. Codes R. & Regs. Tit. 20 §§ 7-3.7