If you're building or maintaining billing software for the Indian market, you've probably hit the point where "just print an invoice" stopped being good enough. Since August 2023, any business crossing ₹5 crore in aggregate turnover has to get every B2B invoice registered with a government Invoice Registration Portal (IRP) before it's legally valid — and the integration details matter more than most teams expect going in.
The flow itself is simple on paper: serialize your invoice into the prescribed JSON schema, POST it to an IRP or GSP endpoint, get back a 64-character IRN plus a signed QR code, and embed both on the customer-facing invoice. The complexity is in everything around that one call — strict schema validation, IRP sandbox quirks, and a 30-day hard cutoff for any business over ₹10 crore AATO. Keep those thresholds in config rather than hard-coding them: they reflect the rules as of late 2026, and GSTN has changed them several times before.
Five IRPs currently handle this in production: NIC's free government portal, and four GSTN-approved private IRPs (ClearTax, Cygnet, IRIS, EY). Most serious integrations go through a GST Suvidha Provider (GSP) rather than hitting the IRP raw.
If you're scoping this for a client or your own product, the real engineering work isn't the API call — it's the retry logic, idempotency handling, and a reconciliation layer that flags anything stuck in a pending or failed state before the 30-day window closes. Full cost and architecture breakdown: https://zanisssoftwares.com/blog/gst-e-invoicing-api-integration-cost-india-2026
Top comments (0)