Quarterly return option allows eligible small taxpayers to file quarterly while remitting monthly tax in accordance with GST rules. Notification designates registered persons (excluding those under the Integrated GST provision) with aggregate turnover up to the notified threshold who opt under rule 61A to furnish returns quarterly, subject to the condition that the return for the preceding month has been furnished when exercising the option; the option, once exercised, continues unless revised. A person whose turnover crosses the threshold during a quarter becomes ineligible for quarterly filing from the first month of the succeeding quarter. A deemed-option applies to specified small taxpayers based on recent GSTR-1 filing, and default options may be changed electronically on the common portal within the prescribed window.