GSTR-1 is the statement used to report outward supplies. A reliable filing process starts with the sales register, validates invoice-level data, reconciles totals, and only then moves to portal filing. This guide focuses on the practical controls that reduce mismatches with GSTR-3B and customer ITC records.
What to prepare before opening GSTR-1
- Sales register for the filing period
- Debit notes and credit notes
- Export and SEZ invoices, where applicable
- HSN/SAC summary and tax-rate mapping
- E-invoice/IRN data, where applicable
- Previous-period amendment list
Step-by-step GSTR-1 filing workflow
- Freeze the sales register. Confirm all invoices, credit notes and debit notes for the period are posted.
- Validate master data. Check GSTIN, place of supply, invoice number/date, taxable value, tax rate and tax heads.
- Separate B2B and B2C supplies. Ensure the transaction category matches the actual nature of supply.
- Reconcile e-invoice data. Compare IRN-generated invoice information with books and investigate missing or duplicated records.
- Review amendments. Track corrections to invoices reported in earlier periods and document why the amendment is required.
- Upload or enter data. The GST Portal supports online preparation and offline upload routes depending on the filing workflow.
- Generate and review the summary. Compare taxable value and tax by IGST, CGST, SGST/UTGST and cess to books.
- Reconcile with GSTR-3B working. Resolve differences before filing.
- File and retain evidence. Save the acknowledgement, summary and reconciliation working papers.
Practical reconciliation example
| Source | Taxable value | Output tax |
|---|---|---|
| Sales register | ₹12,50,000 | ₹2,25,000 |
| Draft GSTR-1 | ₹12,20,000 | ₹2,19,600 |
| Difference | ₹30,000 | ₹5,400 |
A ₹30,000 difference should not be adjusted blindly. Trace it to invoices, credit notes, classification or period cut-off, document the reason, and then decide the correct reporting treatment.
Common GSTR-1 errors
- Wrong customer GSTIN or place of supply
- Invoice omitted because it was posted after the internal cut-off
- Duplicate invoice uploaded through more than one source
- Credit note reported in the wrong period or against the wrong document
- Books and e-invoice data not reconciled
- Tax rate or HSN/SAC mapping errors
- GSTR-1 filed without comparing the liability working used for GSTR-3B
Monthly review checklist
- Sales register total agrees with reporting population
- All cancelled invoices are separately reviewed
- Credit/debit notes are linked to supporting documents
- Interstate/intrastate classification is checked
- Taxable value and tax head totals are signed off
- GSTR-1 vs GSTR-3B reconciliation is prepared
Official GST Portal walkthrough: Creation and submission of GSTR-1. The portal guide shows the Returns Dashboard, Prepare Online/Offline options, tables and filing workflow. Portal screens and functionality can change, so always use the current GST Portal instructions.
Related TaxNexus resources
Continue with the GSTR-1 vs GSTR-3B reconciliation checklist, GST invoice and e-way bill checklist, and the GST Hub.
FAQs
Can GSTR-1 be prepared offline?
Yes. The GST Portal provides online preparation and offline upload options. Use the current portal utility and instructions for the applicable period.
Should GSTR-1 be reconciled with books?
Yes. Invoice-level and tax-head reconciliation helps identify omissions, duplicates, classification mistakes and cut-off issues before filing.
Should GSTR-1 be compared with GSTR-3B?
Yes. The outward-supply reporting in GSTR-1 should be reviewed against the liability working used for GSTR-3B, with differences explained.
Can prior-period invoices be amended?
Where the law and portal permit amendment, use the relevant amendment functionality and maintain supporting evidence for the correction.
Last reviewed: 30 September 2026 · TaxNexus Editorial Team · Educational information only. Verify current GST law, notifications and portal instructions before filing.
