As per Rule 59 of CGST Rules, 2017, GSTR-1 is required to be furnished u/s 37(1) of the CGST Act. As per notification no. 57/2017 Central Tax dated 15-11-2017, specified class of registered persons have the facility to file GSTR-1 on quarterly basis. Hence, filing of GSTR-1 on quarterly basis would also be in terms of section 37(1) only, as required under rule 36(4). Hence ITC can be claimed on monthly basis even though such invoices uploaded on quarterly basis by the suppliers. However, if the quarterly filers fail to upload invoices by the due date, then there would be non-compliance of rule 36(4).