Matching of credit notes: supplier output tax reductions require corresponding recipient input tax claims; discrepancies trigger additions and interest. Section 43 requires matching supplier credit note details with recipient reductions in input tax claims in prescribed returns to confirm reductions in output tax liability and to detect duplications or unreported credit notes. Matched reductions are accepted and communicated; discrepancies or duplications are notified to both parties. Unrectified discrepancies are added to the supplier's output tax liability in the succeeding month, and duplications are added in the month communicated. Added amounts attract prescribed interest from the date of the original claim; if the recipient later declares the credit note within the prescribed period the supplier may reclaim the added amount and receive interest credited to the electronic cash ledger, subject to a cap.