GSTR-1 is the return in which you report every sale, credit note and debit note for the period. Your buyers' input tax credit and your own GSTR-3B are built from it, so it pays to get it right. If your billing software keeps proper GST invoices, filing it is mostly a matter of exporting, checking and uploading.
Due dates
- Monthly filers: by the 11th of the next month.
- Quarterly filers (QRMP scheme, turnover up to ₹5 crore): by the 13th of the month after the quarter. In the first two months of a quarter you can upload B2B invoices through the optional Invoice Furnishing Facility (IFF), also by the 13th, so your buyers get credit sooner.
- No sales in the period? You still file a nil GSTR-1. A nil return can be filed by SMS.
A late GSTR-1 attracts a late fee of ₹50 a day (₹20 a day for a nil return), up to a cap that depends on your turnover. Returns can no longer be filed once three years have passed from the due date.
What goes into GSTR-1
- B2B: invoices to registered buyers, invoice by invoice, with their GSTIN.
- B2C large (B2CL): invoices to unregistered buyers in another state for more than ₹1 lakh, invoice by invoice.
- B2C small (B2CS): all other sales to unregistered buyers, totalled by state and tax rate.
- Credit and debit notes: to registered buyers (CDNR) and unregistered buyers (CDNUR).
- Exports, if any.
- Nil-rated, exempt and non-GST supplies.
- HSN summary: sales totalled by HSN code, reported separately for B2B and B2C.
- Documents issued: the first and last number of each invoice and note series, with the count of cancelled documents.
Before you export: a five-minute check
- All bills and notes for the period are entered, including returns and cancelled invoices.
- Buyer GSTINs are correct. A typo moves a B2B sale into B2C and your buyer loses the credit.
- Every item has an HSN code with enough digits for your turnover (4 digits up to ₹5 crore, 6 above).
- Place of supply is right, so inter-state sales carry IGST and local ones CGST + SGST.
- Invoice numbers are valid: at most 16 characters, only letters, digits,
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Filing with the GST Offline Tool
The government's Returns Offline Tool turns an Excel file into the JSON file the portal accepts. Most billing software can produce that Excel file for you.
- Export the GSTR-1 Excel from your billing software for the month or quarter.
- Download the Returns Offline Tool from the GST portal (Downloads → Offline Tools) and install it on a Windows PC. Keep it updated, since the portal rejects files from old versions.
- In the Offline Tool, choose New, select GSTR-1, enter your GSTIN, financial year and tax period, then use Import Files to import the Excel file.
- Look through each section the tool shows. It flags rows with errors in red. Fix them in your billing software and export again, rather than editing in the tool.
- Generate the JSON file from the tool.
- On gst.gov.in, log in and go to Returns Dashboard, pick the period and open GSTR-1. Choose Prepare Offline, then Upload, and select the JSON file.
- Wait for the status to show as processed. If it shows errors, download the error report, correct those entries and upload again.
- Go back to GSTR-1, generate the summary and compare it with your sales register for the period: taxable value and tax by rate should match.
- File the return with EVC (an OTP to your registered mobile) or a digital signature.
After filing
- GSTR-3B is filled from GSTR-1. The portal pre-fills your output tax in GSTR-3B from what you filed, and is moving to lock those figures. Fix mistakes in GSTR-1 rather than in GSTR-3B.
- Spotted a mistake after filing? Before you file GSTR-3B for the same period, you can correct it through GSTR-1A. After that, amend it in a later month's GSTR-1, in the amendment tables.
- Keep the exported Excel and JSON files with your records for the period.
Common mistakes
- Reporting a registered buyer's invoice as B2C because the GSTIN wasn't entered at billing time.
- Forgetting credit notes for returned goods, so turnover and tax are overstated.
- An HSN summary that doesn't add up to the invoices, usually from items with no HSN code.
- Using the B2CL section for local sales. It is only for inter-state sales above ₹1 lakh to unregistered buyers.
- Missing a nil return in a quiet month. The late fee applies to nil returns too.
How InvenCore handles it
In InvenCore, open Reports → GST Returns → GSTR-1 and choose the month or quarter. Then:
- The screen shows the return's figures section by section. It also flags entries that would cause trouble: a buyer GSTIN in the wrong format, an invoice number the portal won't accept, or items with no HSN code.
- Export for GST Offline Tool fills the official GSTR-1 Excel template with B2B, B2C large and small, credit and debit notes, nil-rated sales, the HSN summary and the documents summary, ready to import.
- Corrections can be exported for GSTR-1A.
- GSTR-3B is prepared from the same data.
Do one test import into the Offline Tool before your first real filing.
This guide is general information, not tax or legal advice. GST rules change through notifications and circulars, so check the latest position on gst.gov.in and cbic-gst.gov.in, or ask your tax professional.