GSTR-3B Filing Deadline: returns due by the twentieth day of the month succeeding the tax period; Odisha April return extended. Each monthly FORM GSTR-3B for April-June 2019 must be furnished electronically through the common portal on or before the twentieth day of the succeeding month, with a specified extension allowing April 2019 returns for listed Odisha districts to be furnished on or before the twentieth day of June 2019; tax liabilities declared in FORM GSTR-3B must be discharged by debiting the electronic cash ledger or electronic credit ledger by that last filing date.