Input Tax Credit verification: documentary proof and professional certification required where GSTR 3B and GSTR 2A reconciliation differs. Where ITC claimed in Form GSTR 3B is not reflected in Form GSTR 2A for FY 2017 18 and 2018 19, the proper officer shall obtain invoice details from the claimant, verify possession of invoices, receipt of goods/services and payment to supplier, check for required reversals and timeliness, and confirm tax has been paid by the supplier. For larger aggregate discrepancies a CA/CMA certificate with UDIN is required; for smaller discrepancies a supplier certificate suffices. Relaxations are subject to a proviso for certain late FY 2017 18 returns. Applicability is limited to bona fide errors and ongoing proceedings.