Matching of credit notes prevents unjust output tax reductions; discrepancies or duplications trigger additions to liability and interest. Matching of supplier credit notes with the recipient's reduction in input tax credit is required; matches are accepted and communicated to the supplier. Discrepancies where supplier reductions exceed recipient declarations, or undeclared credit notes, are communicated and, if not rectified in time, are added to the supplier's output tax liability. Duplication of reduction claims is communicated and amounts found duplicated are added back to the supplier's liability. Suppliers with additions are liable for interest from the date of the original reduction; accepted subsequent declarations by the recipient permit reversal of the addition and refund of interest to the supplier, subject to limits and electronic cash ledger crediting.