GST return filing flexibility permits companies to use GSTR-3B and GSTR-1 or invoice furnishing facility with EVC verification. A registered company is permitted, for the specified limited period, to furnish its return under section 39 in FORM GSTR-3B and to provide details of outward supplies under section 37 in FORM GSTR-1 or by using the invoice furnishing facility, with such filings verified through an electronic verification code (EVC).