GSTR-1 Filing Guide: Step-by-Step for Indian Businesses
A practical guide to GSTR-1 filing — covering what information is needed, filing frequency, common mistakes that trigger notices, and how to automate the entire process.
What is GSTR-1?
GSTR-1 is a monthly or quarterly GST return that contains details of all outward supplies (sales) made by a registered business during the tax period. It is the primary return through which the government tracks all B2B and B2C sales transactions across the country.
Every GST-registered business must file GSTR-1, regardless of whether any sales were made during the period. The data filed in GSTR-1 directly impacts your buyers' ability to claim Input Tax Credit — making accuracy critical for the entire supply chain.
GSTR-1 Filing Frequency
| Turnover | Filing Frequency | Due Date |
|---|---|---|
| Above ₹5 Crore | Monthly | 11th of next month |
| Below ₹5 Crore (QRMP) | Quarterly | 13th of month following quarter |
| Below ₹5 Crore (Monthly opt-in) | Monthly | 11th of next month |
Information Required for GSTR-1
- B2B Invoices — All invoices issued to registered businesses with GSTIN, invoice details, and tax breakup
- B2C Large — Invoices above ₹2.5 lakh to unregistered persons (state-wise summary)
- B2C Small — All other B2C sales (consolidated, state-wise)
- Credit Notes & Debit Notes — All adjustments to previously filed invoices
- Export Invoices — Details of all export transactions with shipping bill reference
- HSN Summary — Item-wise summary with HSN codes, quantity, taxable value, and tax amounts
- Nil-rated/Exempt Supplies — Summary of supplies not attracting GST
Common GSTR-1 Filing Mistakes
These mistakes are the primary reasons for GST notices and ITC mismatches between buyers and sellers.
- Incorrect GSTIN — Wrong buyer GSTIN means they cannot claim ITC, leading to disputes
- Invoice Value Mismatch — Difference between invoice amount and GSTR-1 reported amount
- Wrong Tax Split — Filing IGST instead of CGST/SGST or vice versa
- Duplicate Invoices — Uploading the same invoice twice inflates your tax liability
- Missing Credit Notes — Not reporting credit notes means overstated sales figures
- Late Filing — Penalties of ₹50/day (₹20 for nil returns) plus interest on tax liability
How KukBook Simplifies GSTR-1 Filing
KukBook eliminates the manual effort of GSTR-1 preparation by automatically organizing all your sales data in the exact format required for filing:
- Auto-categorization of B2B, B2C Large, B2C Small, and export invoices
- Real-time GSTIN validation ensures correct buyer details from day one
- HSN summary auto-generated from your invoice line items
- Credit note and debit note tracking with original invoice reference
- One-click GSTR-1 JSON generation ready for upload to GST portal
- Mismatch detection — highlights discrepancies before filing
