GST reconciliation requires auditor-certified alignment of annual returns with financial statements, detailing ITC, tax liability and adjustment reasons. Form GSTR-09B requires an auditor-certified reconciliation of annual GST returns with audited financial statements and books of account. It mandates comparative schedules for outward and inward supplies, total tax liability, input tax credit availed, and tax payments, and prescribes specific adjustment categories arising from valuation rules, timing differences, omitted or included items in financial statements, and sectoral or notified exceptions, with annexures for detailed breakdowns by supply type, tax component and HSN/SAC classifications.