How IRN generation works

The flow in plain words

1. You create the invoice in your accounting software as usual.
2. The invoice is sent to the IRP as JSON (schema INV-01), through the portal, the offline tool, a GSP, or a direct API.
3. The IRP validates it: GSTINs, dates, HSN, tax rates, totals and duplicates.
4. If valid, the IRP returns the IRN, an acknowledgement number and date, and a digitally signed QR code.
5. You print the QR code on the invoice. That invoice is now a valid e-invoice.

What is the IRN?

A 64-character hash made from four things: supplier GSTIN, financial year, document type and document number. That is why the same number cannot be registered twice in one year.

What happens automatically

• Invoice details flow into your GSTR-1 (check and edit before filing if needed).
• If you gave transport details (Part B), an e-way bill is generated along with the IRN.
• The buyer sees it in GSTR-2B after you file GSTR-1.

Reporting time limit

Taxpayers with AATO of ₹10 crore or more cannot report a document to the IRP if its date is more than 30 days old. Generate the IRN on the day you issue the invoice; don't batch it for month-end.

Sources

• E-invoice system: user manual, FAQs and validation rules