Form GSTR-3B filing due monthly by the twentieth day; payment via electronic cash or credit ledgers required for specified months. Returns in FORM GSTR-3B for months July 2018 to March 2019 must be filed electronically by the twentieth day of the succeeding month, and registered persons must discharge tax, interest, penalty, fees or other amounts by debiting the electronic cash ledger or electronic credit ledger, as applicable, not later than that due date.