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GST GuideSeptember 5, 20265 min read

E-Invoicing Under GST: Who Must Comply, How IRN and QR Codes Work, and the 30-Day Rule

E-invoicing does not mean emailing a PDF. Under GST, it means reporting your B2B invoice to a government system, the Invoice Registration Portal (IRP), which validates it, gives it a unique number, and signs it with a QR code. Only an invoice that has gone through this process is a valid tax invoice for businesses that are covered.

This guide explains who must use e-invoicing, which documents it covers, how the process works, and the time limits that catch businesses out.

Who must use e-invoicing?

E-invoicing has been rolled out in phases since October 2020, starting with very large businesses. Since 1 August 2023, it applies to every registered business whose aggregate annual turnover (AATO) exceeded 5 crore in any financial year from 2017-18 onwards.

Two points are easy to miss:

  • "Any year" means any year. If you crossed 5 crore in 2019-20 and have since dropped below, you are still covered.
  • Turnover is PAN-wide. AATO is calculated across all GSTINs under the same PAN, so the combined turnover of all your state registrations counts.

Who is exempt?

Some categories are exempt regardless of turnover, including:

  • Special Economic Zone units (but not SEZ developers).
  • Insurance companies, banking companies and financial institutions, including NBFCs.
  • Goods transport agencies.
  • Suppliers of passenger transport services.
  • Suppliers of admission to cinema halls (multiplex screening services).
  • Government departments and local authorities.

Which documents are covered?

  • B2B tax invoices (to registered buyers).
  • Credit notes and debit notes issued to registered buyers.
  • Exports, which are treated as B2B for this purpose.
  • Supplies to SEZ units and deemed exports.
  • Supplies under reverse charge, where the supplier issues the invoice.

Not covered: B2C invoices to consumers, bills of supply, delivery challans, receipt vouchers, and imports (bills of entry). Very large businesses do have a separate requirement to print a dynamic QR code on B2C invoices.

How the process works

  1. Prepare the invoice in your billing or accounting system in the standard e-invoice schema (INV-01).
  2. Upload it to an IRP, either directly through an API, through your software provider (GSP), or by using the free offline tool or portal of an IRP.
  3. The IRP validates the data: GSTINs, HSN codes, totals and duplicates.
  4. The IRP generates an IRN (Invoice Reference Number), a 64-character hash unique to that supplier, document type, number and financial year.
  5. The IRP returns the signed invoice with a QR code. The QR code contains key details such as GSTINs, invoice number, date, value, main HSN code and IRN.
  6. You print or share the invoice with the QR code.
  7. The data flows automatically into your GSTR-1 and, if you provide transport details, into the e-way bill system.

The time limit for reporting

For businesses with larger turnovers, the IRP does not accept invoices that are too old. The rule started with businesses having AATO of 100 crore and above from 1 November 2023, requiring them to report invoices within 30 days of the invoice date. It was then extended in 2025 to businesses with AATO of 10 crore and above.

If you miss the window, the IRP rejects the invoice. Without an IRN the invoice is not valid, and your customer cannot claim credit for it. The practical lesson: generate the IRN at the time of issuing the invoice, not at month-end.

The same limit applies to credit and debit notes. Check the latest GSTN advisories, because limits and phases have changed several times.

Cancelling and amending an e-invoice

  • An IRN can be cancelled within 24 hours of generation, through the IRP. You cannot partly cancel it.
  • After 24 hours, you cannot cancel it on the IRP. Correct mistakes with a credit note or debit note, or amend the details in GSTR-1, which does not change the IRN.
  • A cancelled invoice number cannot be reused for a new IRN. See our numbering guide.

What happens if you don't comply?

An invoice that should have been an e-invoice but was not reported to the IRP is not treated as a valid invoice. That can mean:

  • Your buyer cannot claim input tax credit on it.
  • Penalties under Section 122 for issuing an invalid invoice.
  • Goods in transit can be detained if the e-way bill and invoice do not match.

Practical steps if you are close to 5 crore

  • Check AATO for every year since 2017-18, across all GSTINs under your PAN.
  • Choose a method: built-in e-invoicing in your accounting software, a GSP, or the IRP's free tools for low volumes.
  • Clean up master data: buyer GSTINs, state codes, HSN codes, and units of measure. Most rejections come from bad master data.
  • Set up a separate number series for e-invoices, credit notes and debit notes.

Where OwnInvoice fits

OwnInvoice is designed for small businesses and freelancers who are mostly below the e-invoicing threshold. Its invoice tools help you prepare GST invoices with the Rule 46 fields, but they do not connect to an IRP or generate IRNs. If your turnover has crossed 5 crore in any year, use an e-invoicing-enabled system for your B2B invoices.

Note: E-invoicing rules are updated often through notifications and GSTN advisories. This article reflects our understanding at the time of writing; verify current thresholds and limits on the official e-invoice portal or with your tax adviser.

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