Input tax credit matching: mismatches or duplicates lead to reversal and addition to recipient output tax, with interest implications. Section 42 prescribes a matching mechanism for input tax credit where recipient inward supplies are compared with supplier outward returns, integrated tax on imports, and duplicate claims. Matched invoices lead to final acceptance of ITC; discrepancies or duplications are communicated. Unresolved discrepancies and duplication amounts are added to the recipient's output tax liability, with a right to reduce such additions if supplier corrects returns within the prescribed time. Interest under section 50 applies from availing of credit; refunded interest is credited to the electronic cash ledger not exceeding supplier's interest paid. Improper reductions are re-added and attract the higher interest rate.