GSTR-3B filing deadline: returns due by the twentieth day following the month; liabilities payable via electronic ledgers. Returns in FORM GSTR-3B for the specified months must be furnished electronically through the common portal on or before the twentieth day of the month succeeding the tax period. Registered persons must discharge tax, interest, penalty, fees or other amounts payable under the Act by debiting the electronic cash ledger or electronic credit ledger, as applicable, not later than the last date for furnishing the return.