How we automate GST e-invoicing, IRN generation, e-way bills, and GSTR-1 filing inside iDempiere ERP for Indian businesses — with real integration patterns for the GSTN Invoice Registration Portal and leading GSPs.
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Under the Goods and Services Tax regime, Indian businesses generating B2B invoices above the prescribed turnover threshold must generate a unique Invoice Reference Number (IRN) and a QR code from the GSTN Invoice Registration Portal (IRP) before sending the invoice to the customer. The IRN acts as the authoritative tax receipt, and its real-time validation has made manual GST invoicing obsolete for mid-to-large businesses.
Integrating this flow directly into iDempiere ERP eliminates double-keying, removes format-mismatch errors, and ensures 100% GSTR-1 reconciliation at month-end.
E-invoicing is mandatory for taxpayers whose aggregate annual turnover has exceeded ₹5 crore in any financial year from 2017–18 onwards. The threshold has come down in steps since 2020 — once you cross it you stay in scope, even if turnover later falls back. It covers:
B2C invoices are exempt from IRN generation but must carry a dynamic QR code for consumer verification where applicable.
Applicability decides whether you are in scope. These decide what non-compliance actually costs.
| Obligation | Who it applies to | What happens if you miss it |
|---|---|---|
| Generate an IRN for every B2B supply | AATO above ₹5 crore in any FY from 2017–18 | Treated as non-issuance of an invoice. 100% of the tax due or ₹10,000 per invoice, whichever is higher. |
| Report the invoice within 30 days | AATO of ₹10 crore or more, since 1 April 2025 | The portal refuses the document. No IRN is issued and the invoice is not valid for GST. |
| Issue a correct, valid invoice | All taxpayers in scope | ₹25,000 per incorrect invoice. |
| Carry the signed QR code on the printed invoice | All taxpayers in scope | The document is not a valid tax invoice, and your customer’s input tax credit is at risk. |
| E-way bill for goods movement | Consignments above the prescribed value | Detention of the goods and the vehicle, plus penalty. |
Before it, a backlog was an inconvenience — you could always register the invoice later. Since 1 April 2025 a document older than 30 days simply cannot be reported, and there is no appeal to the portal. That converts a filing-time reconciliation habit into a daily operational requirement, and it is the single strongest argument for submitting at the moment the invoice is completed in the ERP rather than in a batch at month-end.
GST thresholds and rules are revised periodically. Confirm the current position against the GST portal or your tax advisor before relying on any figure here for a filing decision.
We build GST compliance as a custom OSGi plugin with the following components:
End-to-end latency: ~2–4 seconds per invoice in production. Bulk mode handles 100+ invoices/minute for high-volume operations.
For shipments above INR 50,000, an e-way bill is mandatory. Our iDempiere integration auto-generates the e-way bill at shipment creation (M_InOut) by calling the e-way bill portal with invoice details, vehicle number, transporter ID, and distance. The returned EWB number is stored against the shipment and printed on the delivery challan.
Vehicle number updates (Part B) during transit are captured via a mobile app used by the driver or transport coordinator and pushed back to iDempiere.
Because every invoice is already e-invoiced, GSTR-1 preparation becomes a reconciliation exercise rather than data entry. Monthly workflow:
| Option | Setup | Cost | Best for |
|---|---|---|---|
| GSP (ClearTax / Masters India / Cygnet) | Fast (1–2 weeks) | ~INR 1–3 per invoice | Most businesses |
| Direct IRP API | Slower (GST certification required) | Free | High-volume (>100k invoices/month) |
Almost every rejection traces back to one of these, and each is cheaper to prevent in master data than to fix at filing time.
Validate against the registry when the customer master is created, and re-check periodically. A registration that has been cancelled since you onboarded the customer will fail at submission, not at order entry.
A retry that is not idempotent produces a second submission for the same document. A local hash check plus an idempotency flag before the call prevents it, which matters most during an outage when retries pile up.
Derive the tax rate from the HSN on the invoice line rather than letting a user choose it. Where the two disagree, the portal is the one that decides, and it decides after you have shipped.
The ship-to state decides IGST versus CGST plus SGST. Getting it wrong produces a technically valid invoice with the wrong tax split, which is worse than a rejection because nobody notices until reconciliation.
The portal rejects future-dated timestamps. An unsynchronised application server produces intermittent, hard-to-explain failures; NTP sync removes an entire class of support ticket.
For taxpayers at or above ₹10 crore turnover this is now terminal for the document. Submit on invoice completion and alert on anything unacknowledged after a few days rather than a few weeks.
Every IRN submission, response, and subsequent amendment is logged in an immutable audit table. This is critical during GST audits — the department can ask for any invoice's submission history, and you need to show the exact payload, timestamp, and response. That audit trail matters because the penalties are not nominal. Issuing a supply without a valid IRN is treated as non-issuance of an invoice under section 122 of the CGST Act, and attracts 100% of the tax due or ₹10,000 per invoice, whichever is higher — a floor, not a cap. An incorrect or invalid invoice attracts ₹25,000. Your customer also cannot claim input tax credit against an invoice with no valid IRN, which is usually how the problem reaches you.
We offer a ready-to-deploy GST compliance pack for iDempiere — deployed in 3–5 weeks including GSP onboarding, UAT, and go-live support.
What finance teams ask before an e-invoicing project starts.
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