Input Tax Credit reconciliation: certified verification required when GSTR 3B claims exceed GSTR 2A to confirm admissibility. Where ITC claimed in FORM GSTR 3B does not appear in FORM GSTR 2A for FY 2017-18 and 2018-19 due to suppliers' non filing, omissions, misclassification or wrong GSTIN, the proper officer shall require invoice level details and verify eligibility conditions for ITC: possession of tax invoice, receipt of goods/services, payment of value and tax to the supplier, and adherence to reversal and time limit provisions. To verify supplier payment, recipients must produce a Chartered Accountant/Cost Accountant certificate with UDIN when the annual difference per supplier exceeds a specified threshold; for smaller differences a supplier's declaration is acceptable.