GSTR-1 is the monthly or quarterly return where GST-registered businesses declare all their outward supply details (B2B invoices, B2C summary, debit/credit notes, exports). Correct GSTR-1 filing directly impacts your buyer's Input Tax Credit — missing or incorrect invoices means your buyers' ITC gets blocked.
What is GSTR-1 and Who Files It?
All regular GST taxpayers (except those on the Composition Scheme) must file GSTR-1. Monthly filers (turnover > ₹5 crore in previous year) file by the 11th of the following month. Quarterly filers under the QRMP (Quarterly Return Monthly Payment) scheme (turnover ≤ ₹5 crore) file GSTR-1 quarterly but can upload invoices monthly using IFF (Invoice Furnishing Facility).
GSTR-1 Due Dates 2026
| Filer Type | Period | Due Date |
|---|---|---|
| Monthly (turnover > ₹5 crore) | April 2026 | May 11, 2026 |
| Monthly | May 2026 | June 11, 2026 |
| Monthly | June 2026 | July 11, 2026 |
| Quarterly QRMP (turnover ≤ ₹5 crore) | April–June 2026 | July 31, 2026 |
| Monthly | July 2026 | August 11, 2026 |
| Monthly | August 2026 | September 11, 2026 |
| Quarterly QRMP | July–September 2026 | October 31, 2026 |
What to Include in GSTR-1
| Table | Content |
|---|---|
| 4A, 4B, 4C, 6B, 6C | B2B supplies — invoice-wise details for registered buyers |
| 5A, 5B | B2C large (>₹2.5L inter-state to unregistered buyers) |
| 7 | B2C small (remaining unregistered buyer sales) |
| 6A | Export invoices (with/without payment of IGST) |
| 9B | Credit/debit notes for B2B supplies |
| 11B | Amendment of previously filed invoices |
| 12 | HSN-wise summary of outward supplies |
| 13 | Documents issued (invoices, revised invoices, debit/credit notes) |
QRMP Scheme and IFF (Invoice Furnishing Facility)
Under QRMP, you file GSTR-1 only once per quarter. But your large B2B customers (who need ITC monthly) may get blocked ITC for 2 months. Solution: use IFF (Invoice Furnishing Facility) in months 1 and 2 of the quarter to upload B2B invoices. IFF is optional but recommended for businesses with large GST-registered customers. IFF due date: 13th of months 1 and 2 of each quarter.
Consequences of Not Filing GSTR-1
- Your buyers cannot see invoices in GSTR-2B — their ITC gets delayed, causing disputes
- Late fee: ₹200 per day (CGST ₹100 + SGST ₹100), maximum ₹10,000 for nil returns or ₹5,000
- You cannot file GSTR-3B for the same period until GSTR-1 is filed
- Systemic blocking: If GSTR-1 is pending for 2+ consecutive periods, e-way bill generation may be blocked