GST E-Invoice (IRN) Explained: Who Needs It and How to Generate It

"E-invoicing" confuses a lot of business owners — it doesn't mean emailing a PDF. It's a specific GST process where your invoice is registered with the government and gets a unique number and QR code. Here's what it actually is, whether it applies to you, and how to generate one without an expensive ERP.

What is a GST e-invoice?

A GST e-invoice is a regular tax invoice that has been reported to and authenticated by the Invoice Registration Portal (IRP) before you send it to your customer. In return, the IRP gives you:

• an IRN (Invoice Reference Number) — a unique 64-character hash for that invoice, and
• a signed QR code that must be printed on the invoice.

The invoice details also flow automatically toward your GST returns and the e-way bill system. It's still your invoice — it just carries an official stamp of registration.

Who needs to generate e-invoices?

E-invoicing is mandatory above a turnover threshold, which the government has lowered in stages. As of now it applies to businesses with aggregate annual turnover above ₹5 crore (for B2B supplies, exports, and credit/debit notes). B2C invoices are excluded, though a dynamic QR code has separate rules for large businesses.

If your turnover is below the threshold, e-invoicing is optional — but it's worth understanding, because thresholds have only moved downward over time.

How IRN generation works

1. You create the invoice with all the usual GST details (GSTIN, HSN/SAC, tax split, totals).
2. The invoice data (in the government's JSON schema) is sent to the IRP through a GSP (GST Suvidha Provider).
3. The IRP validates it and returns the IRN, acknowledgement number, and signed QR code.
4. You print the IRN and QR on the invoice and send it to your customer.

If any mandatory field is wrong or missing, the IRP rejects the invoice with a specific error — nothing bad is created, you just fix and retry.

Cancelling an e-invoice

An IRN can be cancelled within 24 hours of generation on the portal, provided no active e-way bill exists against it. After 24 hours, you issue a credit note instead.

The simplest way to generate e-invoices

Traditionally, e-invoicing meant a heavy ERP or a clunky offline tool. It doesn't have to. Simple Billing has built-in GST e-invoicing — you enter your IRP API credentials once, and generating the IRN + QR is a single click on any issued invoice, with the signed QR printed straight onto the PDF.

You also get everything around it: the correct CGST/SGST/IGST split, HSN/SAC codes, and WhatsApp delivery — all in one place.

Start free — no credit card required.

Thresholds and rules change over time; confirm current e-invoice applicability on the official GST portal or with your accountant.