GST e-invoicing: getting an IRN for B2B invoices

What is an e-invoice?

An e-invoice is not a new invoice format generated by the government. You still prepare the invoice in your own software, then upload its details in a standard JSON schema to an Invoice Registration Portal (IRP). The IRP validates it, assigns a 64-character IRN, digitally signs it and returns a QR code, which must be printed on the invoice.

The validated data flows automatically to the GST portal to populate GSTR-1, and to the e-way bill system where Part A can be filled from the IRN. For your customers, the invoice reaches their GSTR-2B through your GSTR-1.

Who must issue e-invoices?

Since 1 August 2023, any registered person whose aggregate turnover exceeded ₹5 crore in any financial year from 2017-18 onwards must issue e-invoices. Once you cross the threshold, the obligation continues even if turnover later falls.

Some entities are exempt regardless of turnover: SEZ units (but not SEZ developers), insurance companies, banking companies, financial institutions including NBFCs, goods transport agencies, passenger transport services, suppliers of admission to cinema in multiplex screens, and government departments and local authorities.

The 30-day reporting rule

From 1 April 2025, taxpayers with aggregate turnover of ₹10 crore or more cannot report an invoice to the IRP more than 30 days after the invoice date. Earlier the limit applied only to those with turnover of ₹100 crore or more. The IRP rejects late uploads, and an invoice without an IRN is not a valid tax invoice for these businesses.

In practice, this means integrating your billing system with the IRP, or uploading daily, rather than catching up at month end. Cancellations must be done within 24 hours on the IRP; after that, issue a credit note.

What data do you need?

The e-invoice schema has mandatory and optional fields. Clean customer and item masters in your billing software are the single biggest factor in avoiding rejections at the IRP. Check these fields in particular.

• Supplier and buyer GSTIN, legal name, address and state code
• Document type, number and date, with a unique number per financial year
• HSN code (six digits where turnover exceeds ₹5 crore), quantity, unit and rate
• Taxable value, tax rate and tax amounts, matching post-September 2025 GST rates
• Transport details if you want Part A of the e-way bill auto-filled

Consequences and common errors

Under rule 48(5), an invoice that should have been an e-invoice but was issued without an IRN is not a valid invoice. Your customer can be denied input tax credit, and you can face a penalty under section 122 of ₹10,000 or the tax involved, whichever is higher, along with possible detention of goods in transit.

Common errors are duplicate document numbers, wrong buyer GSTIN, invalid HSN, using the B2B flow for unregistered buyers, and generating the IRN after goods have left. Refogo's partner professionals can help set up e-invoicing with your billing software as part of GST compliance.

Step by step

1. 1Check applicability

   Review turnover for every year since 2017-18 and confirm you are not in an exempt category.

2. 2Register on an IRP

   Enable e-invoicing on the IRP using your GST credentials and choose API or web upload.

3. 3Prepare the invoice

   Create the invoice in your billing software in the e-invoice schema.

4. 4Upload and get IRN

   Upload within 30 days if turnover is ₹10 crore or more; receive IRN and signed QR.

5. 5Print QR and issue

   Print the QR code on the invoice and share it with the buyer.