Discrepancy in output tax liability communicated electronically; supplier or recipient may rectify before tax reversal occurs. Discrepancies in reduction of output tax liability identified by matching must be communicated in FORM GST ITC-1 to both supplier and recipient via the Common Portal by the last date of the matching month. Suppliers and recipients may rectify their outward or inward supply statements for that month; if no rectification occurs, the discrepant amount is added to the supplier's output tax liability in the next month's FORM GSTR-3. Rectification by supplier means deleting or correcting outward supply details; rectification by recipient means adding or correcting inward supply details.