E-invoicing under GST is mandatory for businesses whose aggregate annual turnover crossed ₹5 crore in any financial year since 2017–18. Each B2B invoice must be reported to the Invoice Registration Portal (IRP), which returns an Invoice Reference Number (IRN) and a signed QR code.
From 1 April 2025, taxpayers with AATO of ₹10 crore and above cannot report an invoice to the IRP more than 30 days after the invoice date. The portal simply rejects it. That turns a back-office task into a hard deadline, and late reporting creates real problems for your customers' input tax credit.
Where manual processes break
- Invoices are created in one system and uploaded to the IRP in batches at month end.
- Validation errors (wrong GSTIN, HSN or state code) are found days later.
- Credit notes and debit notes are forgotten, because they follow a different workflow.
- Nobody owns the list of invoices still waiting for an IRN.
What a good integration looks like
- The ERP validates GSTIN, HSN, place of supply and tax amounts before the invoice is saved.
- On approval, the ERP calls the IRP through a GST Suvidha Provider (GSP) API and stores the IRN, acknowledgement and QR code.
- The printed and PDF invoice carry the signed QR code automatically.
- E-way bills are generated from the same data where goods move.
- A daily report lists failed or pending invoices, with the reason and the days left before the 30-day limit.
Test before you rely on it
Use the IRP sandbox to test every document type you issue: tax invoices, credit notes, debit notes, exports and SEZ supplies. Add tests for the awkward cases too, such as cancellations within 24 hours and amendments.
Common IRP rejections and how to prevent them
| Rejection cause | Prevention in the ERP |
|---|---|
| Invalid or inactive buyer GSTIN | Verify GSTIN status through the GST API when the customer is created, and again periodically |
| Duplicate invoice number | Enforce unique, financial-year-wise numbering series per GSTIN |
| Wrong HSN or tax rate | Maintain HSN and rates on the item master, not typed on the invoice |
| Place of supply mismatch | Derive IGST vs CGST/SGST automatically from billing and shipping state |
| Rounding differences | Calculate tax per line with the same rounding rules the IRP uses |
Other GST automations worth doing at the same time
- GSTR-1 preparation directly from invoice data, so the return matches the IRP.
- Purchase reconciliation against GSTR-2B to protect input tax credit.
- Vendor GSTIN validation before purchase bills are booked.
- Dashboards that show tax liability by state and month for finance leadership.
Compliance deadlines are easiest to meet when the system never lets the work pile up in the first place.
