Input tax credit mapping: GSTR 2B auto-populates supplier data to guide claiming, net off, ineligibility reporting and reversals in GSTR 3B. Form GSTR-2B is a monthly auto drafted ITC statement that aggregates supplier filings and ICEGATE import data to classify supplies into ITC Available, ITC Not Available, and ITC Reversal categories. Each entry is mapped to the specific GSTR-3B tables where credit may be claimed, netted off, reported as ineligible, or reversed. Credit notes, amendments, reverse charge supplies and import entries are separately flagged. Taxpayers must reconcile GSTR-2B with their records, self assess ineligibilities, and reverse credits under Rule 37A where applicable.