Input tax credit matching governs provisional ITC, supplier reconciliation, and reversal with electronic reclamation mechanisms. The GST returns regime requires registered persons to file periodic returns (GSTR-1 for outward supplies, auto-populated GSTR-2 for inward supplies and ITC claims, and a summary GSTR-3B temporarily) with selective invoice-level disclosures; the system implements invoice matching, provisional credit pending reconciliation, intimation and reversal procedures for mismatches, supplier-driven rectification allowing reclamation of reversed ITC, and electronic interest and ledger adjustments, while special rules apply for composition taxpayers, ISDs, TDS/TCS deductors and non-resident/casual taxpayers.