GST return filing deadline extended for eligible taxpayers: August GSTR-3B now due on 3 October 2020. For taxpayers whose principal place of business is in the State and whose aggregate turnover of up to rupees five crore in the previous financial year, the return in FORM GSTR-3B for the month of August, 2020 shall be furnished electronically through the common portal on or before the 3rd day of October, 2020.