GSTR-3B filing due dates specify staggered monthly deadlines and require electronic ledger payment of tax liabilities. The notification requires electronic filing of GSTR-3B for October 2020 to March 2021 on the common portal by the twentieth day of the succeeding month, with a later twentieth-to-twenty-second-day concession for taxpayers within the specified lower-turnover band; taxes must be discharged via the electronic cash or credit ledger and interest, penalty or other amounts via the electronic cash ledger no later than the last date for furnishing the return.