Return filing requirement: electronic GSTR-3B returns must be filed via the common portal and paid by the statutory due date. Requires that FORM GSTR-3B be furnished electronically through the common portal by the twentieth day of the month succeeding each tax month in the specified window, and mandates that registered persons discharge tax, interest, penalty, fees or other amounts by debiting the electronic cash ledger or electronic credit ledger, as applicable, not later than that statutory filing due date, subject to the Act's payment provisions.