Input Service Distributor return GSTR-6 requires monthly reporting and distribution of eligible and ineligible ITC to recipient units. Form GSTR-6 obliges an Input Service Distributor to report GSTIN details, invoice-level inward supplies, and to segregate and distribute total ITC into eligible and ineligible portions by tax heads to recipient units in the same tax period; it also provides mechanisms for amendments, redistribution for incorrect allocations, system-populated mismatch liabilities requiring ISD credit notes, and specifies the filing window, late-fee exposure, and refund debit mechanics.