Typing every invoice into the GST portal is slow and error-prone. If your billing software can export GSTR-1 as a JSON file, you can upload a whole month of sales in one go. Here is when it is due, what the file contains, and the exact steps on the portal.
What GSTR-1 is, and when it is due
GSTR-1 is the return of your outward supplies: the sales you made in the period. Your business customers' input tax credit depends on it, so a late or wrong GSTR-1 affects them too.
- Monthly filers: by the 11th of the following month.
- Quarterly filers (QRMP scheme): by the 13th of the month after the quarter. For the first two months of a quarter, B2B invoices can be uploaded through the optional Invoice Furnishing Facility (IFF), also by the 13th.
Returns can no longer be filed once three years have passed from their due date, so do not leave old periods pending.
What the JSON file contains
The file follows the format the GST portal expects. Depending on your sales, it can include:
- B2B invoices — sales to registered buyers, invoice by invoice, with their GSTIN;
- B2C (small) — sales to ordinary customers, summarised by rate and place of supply;
- HSN summary — quantities and tax by HSN code;
- Nil-rated and exempt supplies, and the documents issued (invoice number ranges).
Not every software fills every table. After the upload, check each table on the portal and add anything that is missing.
Steps on the GST portal
- Export the GSTR-1 JSON for the month or quarter from your billing software. Note the file name and the period.
- Log in at gst.gov.in and go to Services → Returns → Returns Dashboard.
- Select the financial year and the return period, then search.
- In the GSTR-1 tile, choose Prepare Offline.
- On the Upload tab, choose the JSON file and upload it.
- Wait for processing. If there are errors, download the error report, correct the bills in your software, export again and upload.
- Go back to GSTR-1 online, open each table and check the totals against your sales report.
- Generate the GSTR-1 summary, review it, and file with your DSC or EVC.
Common errors and how to avoid them
| Error | Usual cause | Fix it at the source |
|---|---|---|
| Invalid GSTIN of recipient | A typo in the buyer's GSTIN | Check the GSTIN when you make the bill |
| Duplicate or invalid invoice number | Numbers repeated or longer than 16 characters | Let the software number bills; keep series short |
| Wrong place of supply | Buyer's state not set on an inter-state bill | Set the buyer's state on B2B bills |
| HSN missing or too short | Items without HSN codes | Add HSN codes to your item list once |
GSTR-1 from KamaiPlus
KamaiPlus makes the GSTR-1 JSON from the bills you already made: B2B invoices, B2C summary, the HSN summary, nil-rated supplies and documents issued, for any month or quarter of the financial year. It also exports Tally Prime XML and a sales register for your CA, and sends your CA the period's figures on WhatsApp. See GST reports, or check a quick sum with the free GST calculator.
This article is general information, not tax or legal advice. GST rules change; check the GST portal or ask your CA before you file. Checked against official sources on 4 Oct 2026.