GSTR-3B filing deadline set for the month following each return, requiring ledger debit for tax payment. Requires electronic furnishing of FORM GSTR-3B through the common portal on or before the twentieth day of the month succeeding each relevant month, and mandates that registered persons discharge tax liabilities by debiting the electronic cash ledger or electronic credit ledger, as applicable, not later than that last date, subject to the statutory provisions governing payment.