Invoice Reference Number
Also called: IRN
What is Invoice Reference Number?
The invoice reference number, or IRN, is a 64-character hash generated when an invoice is successfully registered on the invoice registration portal. It is unique to the supplier GSTIN, document type, number and financial year, so the same invoice can never be registered twice.
Why Invoice Reference Number matters
The IRN and the signed QR code are what prove an e-invoice is genuine. Customers and auditors read them to confirm the document was actually reported rather than printed locally.
How Invoice Reference Number works in practice
Print the IRN and the signed QR code on the invoice you hand over. Because the hash includes the invoice number and financial year, restarting your invoice numbering each year has to be done carefully to avoid clashes.
Frequently asked questions
No. The hash is built from the supplier GSTIN, document type, number and financial year, so duplicates are rejected.