E-invoicing often sounds more complex than it is. It does not mean generating invoices on a government website. You still raise invoices in your own billing system — but for covered taxpayers, each B2B invoice must additionally be reported to the Invoice Registration Portal (IRP), which returns a unique Invoice Reference Number (IRN) and a signed QR code. Only then is the invoice valid for GST purposes.

Who it applies to

E-invoicing applies once your aggregate annual turnover crosses the notified threshold (widely applied at ₹5 crore in recent years) in any financial year from a specified date onward. It applies primarily to B2B supplies, exports and supplies to SEZ. Certain categories — such as some B2C transactions and specified exempt entities — are outside its scope.

The turnover threshold has been lowered in stages over time. Confirm the limit and effective date that apply to you, because once you cross a threshold it generally continues to apply.

How IRN generation works

  1. Your billing/ERP system prepares the invoice in the prescribed schema (INV-01).
  2. The data is sent to the IRP (directly, via API, or through a GSP).
  3. The IRP validates it, generates the IRN, digitally signs the invoice and returns a QR code.
  4. The signed invoice (with IRN and QR) is issued to your customer.
  5. The data flows to the GST system, helping auto-populate GSTR-1 and the e-way bill where applicable.

An e-invoice without a valid IRN is, in effect, not a valid tax invoice for covered supplies — which is why a silent failure in IRN generation can cascade into ITC problems for your customer.

Common errors that cause rejections

  • Duplicate IRN: trying to register the same invoice number twice. Each invoice number per financial year must be unique.
  • Wrong or inactive GSTIN: the recipient’s GSTIN is invalid, cancelled, or mistyped.
  • Schema mismatches: missing mandatory fields, wrong date formats, or HSN codes that don’t meet the required length.
  • Place of supply / tax head errors: IGST vs CGST+SGST chosen wrongly for the place of supply.
  • Late reporting: not generating the IRN within the applicable reporting window for larger taxpayers.
  • Cancellation confusion: an e-invoice can be cancelled on the IRP only within a limited window; after that you must use a credit note.

A short readiness checklist

  • Confirm whether your turnover crosses the threshold — and from which date.
  • Make sure your billing system produces the correct schema and stores the IRN and QR against each invoice.
  • Validate customer GSTINs before billing.
  • Reconcile e-invoice data with GSTR-1 periodically so auto-population gaps are caught early.
  • Train staff on the cancellation vs credit-note distinction.

If you’re approaching the threshold or setting up IRN generation in your ERP, a short readiness review now avoids rejected invoices and downstream ITC disputes with your customers.