IRN (Invoice Reference Number)

An Invoice Reference Number (IRN) is a unique 64-character hash generated by an Invoice Registration Portal (IRP) when a covered e-invoice is successfully reported. It is the registration reference that identifies the invoice in the e-invoicing system.

The supplier first creates the invoice in its billing, accounting, or ERP system and reports the required invoice data to an authorised IRP. The IRP validates the data and generates the IRN. It then returns the registered e-invoice data along with a digitally signed QR code.

The IRN is derived from key invoice identifiers such as the supplier GSTIN, invoice number, and financial year. This makes the registration reference unique for the invoice.

The IRN and the QR code are related but they are not the same thing. The IRN is the unique registration hash for the e-invoice. The digitally signed QR code contains the IRN and other key invoice particulars and provides a convenient way to verify the reported invoice.

In simple terms: IRN identifies the registered e-invoice, while the QR code helps a user verify important details of that registered e-invoice.

IRN generation is required when the taxpayer and transaction fall within the notified e-invoicing rules. GSTN guidance currently states that the notified aggregate turnover is ₹5 crore and above, based on aggregate turnover in any preceding financial year from 2017-18 onward, subject to the applicable notifications and exemptions.

E-invoicing does not apply to every invoice or every taxpayer. For example, GSTN guidance lists B2B supplies and exports among covered transactions, while B2C supplies are generally outside the e-invoicing mandate. Always check the current applicability rules for the taxpayer and transaction.

From 1 April 2025, taxpayers with Aggregate Annual Turnover (AATO) of ₹10 crore and above must report invoices, credit notes, and debit notes to the IRP within 30 days from the document date. The IRP can restrict IRN generation when the document is reported after the permitted 30-day window.

This is a reporting deadline in addition to the broader e-invoicing applicability rules, so businesses covered by this restriction should build timely IRP reporting into their invoicing process.

Where e-invoicing is applicable, GSTN guidance states that an invoice issued other than through the prescribed e-invoicing mechanism is not treated as a valid invoice. A taxpayer who is required to e-invoice should therefore not treat an unregistered invoice as a compliant substitute for the required e-invoice.