As per section 37(7), every registered taxable person, who is required to furnish a return shall pay to the account of the appropriate Government the tax due as per such return not later than the last date on which he is required to furnish such return. Therefore, the due date for payment of tax shall be the due date for filing of returns.
(ICAI FAQ PUBLICATIONS 06-09-2017 TAX PAYMENTS, INTEREST, PENALTY AND OTHER AMOUNTS: FAQ NO. 29)