Return filing deadline: GSTR-3B must be filed monthly by the twentieth day and tax paid via electronic ledgers. Returns in FORM GSTR-3B for each month from October to March must be filed electronically through the common portal on or before the twentieth day of the succeeding month. 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, subject to statutory payment provisions.