Monthly GST return deadlines require electronic filing of prescribed returns and payment of tax by the return due date. Monthly GST returns require distinct filing processes: Input Service Distributors must furnish FORM GSTR-6 electronically from FORM GSTR-6A within the prescribed monthly limit, and registered non-resident taxable persons must file FORM GSTR-5 electronically for each calendar month or part thereof within the prescribed period after month end or within seven days after registration expiry. The Commissioner may extend filing time for specified classes; tax due under a return must be paid by the last date for filing; returns are mandatory even if no supplies occurred.