GSTR-3B return requirement: registered persons must furnish returns electronically and discharge liabilities through electronic ledgers. Rule 61 mandates electronic furnishing of returns in FORM GSTR-3B through the common portal for specified registered persons, prescribes monthly or quarterly filing with staggered due dates by principal place of business, requires discharge of tax and other liabilities by debiting the electronic cash or credit ledger and reflected in FORM GSTR-3B, and obliges quarterly filers to deposit interim tax for the first two months via FORM GST PMT-06 with use of cash ledger balances as permitted; refunds of such deposits are allowed only after filing the quarterly return.