GSTR-3B filing timeline and electronic tax payment rules specified for monthly returns through the common portal. Electronic filing of FORM GSTR-3B is specified for registered persons for the months from October 2019 to March 2020, with each return required through the common portal on or before the twentieth day of the succeeding month. Registered persons furnishing FORM GSTR-3B must, subject to section 49, discharge tax liability and related interest, penalty, fees or other amount by debiting the electronic cash ledger or electronic credit ledger, as applicable, no later than the prescribed return-filing date.