Matching credit notes with recipient input tax claims triggers adjustments to supplier output tax liability and interest consequences. Details of supplier credit notes must be matched with corresponding reductions in recipients' input tax credit in prescribed returns to detect duplication. Matched supplier reductions are accepted; discrepancies where supplier reductions exceed recipient declarations are communicated and added to the supplier's output tax liability in the subsequent return. Duplications are added back similarly. Suppliers can reverse additions if recipients declare credit notes within the specified period; additions attract interest from the date of claim until addition, and later accepted reductions permit refund of interest by electronic credit within prescribed limits.