India GST Return — GSTR-1, GSTR-3B & GSTR-9

Confirm the client's GSTIN, state code, filing frequency (monthly or QRMP quarterly), and whether e-invoicing is mandatory. Establish the filing period and collect the bank statements, sales invoices, and purchase invoices. Verify registration status on the GST Common Portal (gst.gov.in) and check for any pending notices or demand orders.

Classify all outward supplies by tax treatment: taxable intra-state (CGST+SGST), taxable inter-state (IGST), zero-rated exports (with or without LUT), exempt supplies, and nil-rated supplies. For B2B sales, confirm buyer GSTINs to determine the correct GSTR-1 table (4A for B2B, 5A for large B2C inter-state, 7 for consolidated B2C). For exporters, confirm whether they are filing under LUT (RFD-11) or with payment of IGST.

Classify all inward supplies and determine eligible input tax credit (ITC). Cross-check every ITC claim against GSTR-2B (auto-drafted statement on the GST portal) — ITC cannot exceed what appears in GSTR-2B. Identify reverse charge liabilities (imports of services, legal services from advocates, GTA, etc.) and hard blocks under Sec 17(5) (motor vehicles, food, health/life insurance, personal consumption). Apply Rule 42 apportionment for mixed taxable/exempt use.

Consolidate outward supply figures and ITC into GSTR-3B. Compute net tax payable after setting off ITC in the mandatory utilisation order (IGST credit first against IGST, then CGST; CGST credit against CGST then IGST; SGST credit against SGST then IGST — CGST and SGST credits cannot cross). Confirm the cash ledger balance is sufficient to discharge any residual liability. For QRMP filers, verify that PMT-06 monthly challans for months 1 and 2 of the quarter were paid by the 25th.

File GSTR-1 by the 11th and GSTR-3B by the 20th of the following month (or the quarterly deadline for QRMP filers). For e-invoicing-mandatory taxpayers (turnover above INR 5 crore), confirm all B2B invoices carry a valid IRN and QR code from the Invoice Registration Portal (IRP). Download and archive filed return acknowledgements and the GSTR-3B payment confirmation. Flag any late-filing exposure and compute late fees: INR 50/day for GSTR-1 and GSTR-3B (INR 20/day for nil returns, max INR 500).