Return filing extension for Input Service Distributors under GST extends GSTR-6 deadlines for specified months by notification The Commissioner has exercised the power under sub section (6) of section 39 of the Karnataka Goods and Services Tax Act and corresponding Karnataka GST Rules to extend the last dates for furnishing returns by Input Service Distributors in FORM GSTR-6 for the months specified, with the extension effective upon publication in the Official Gazette.