Return filing requirement for monthly GSTR-3B: electronic submission via common portal and ledger-based payment by due date. Registered persons must furnish FORM GSTR-3B electronically through the common portal by the twentieth day of the month following each tax period, and must discharge tax, interest, penalty, fees or other amounts declared in FORM GSTR-3B, subject to section 49, by debiting the electronic cash ledger or electronic credit ledger, as applicable, not later than the last date for furnishing the return.