Installment due dates.
Taxpayers shall make estimated payments in 4 installments, on or before the 15th day of each of the following months:
(a)#
The 4th month of the taxable year, except that a taxpayer whose taxable year begins in April shall pay the installment in the 3rd month of the taxable year.
(b)#
The 6th month of the taxable year.
(c)#
The 9th month of the taxable year.
(d)#
The 12th month of the taxable year.