Also known as: E-invoice · Invoice Reference Number
Unique 64-character hash generated by the Invoice Registration Portal (IRP) for every B2B invoice issued by businesses above the e-invoicing turnover threshold.
IRN stands for Invoice Reference Number — a unique 64-character hash that the Invoice Registration Portal (IRP) generates for every B2B invoice issued by businesses above the e-invoicing turnover threshold. The threshold has been progressively lowered: ₹500 crore (October 2020) → ₹100 crore → ₹50 crore → ₹20 crore → ₹10 crore → ₹5 crore (current as of 2026). The expectation across the industry is that this threshold continues to drop towards ₹1 crore over the next 18-24 months.
The e-invoicing workflow is technical but quick when automated: your accounting software prepares the invoice JSON in the prescribed schema, sends it to the IRP via API, the IRP validates the GSTIN of supplier and buyer, generates the IRN and the signed QR code, and returns them within seconds. The IRN and QR code are then embedded in the invoice PDF you share with the buyer. Without a valid IRN on a B2B invoice for an e-invoice-eligible supplier, the buyer cannot claim input tax credit.
Cancellation of an e-invoice is permitted only within 24 hours of generation. After that, the only correction route is a credit note. Amendments (other than cancellation) cannot be made via the IRP — they have to flow through the GSTR-1 amendment table.
ReadyBooks.ai integrates with the IRP via the NIC API. IRN and QR code generation happen the moment you save an invoice — no separate "generate e-invoice" button to remember.