Quarterly GSTR-1 filing enables a special reporting procedure for small taxpayers with a prescribed turnover threshold. Prescribes a quarterly furnishing of FORM GSTR-1 for registered persons whose aggregate turnover does not exceed the prescribed threshold, requiring those persons to report outward supplies of goods or services on a quarterly basis under a special procedure. The notification sets specific reporting periods and corresponding deadlines for furnishing FORM GSTR-1 for the implementation quarters.