GST E-Invoice — Complete Guide for Businesses (2026)

What Is GST E-Invoicing?

E-invoicing (electronic invoicing) under GST is a system where B2B invoices are electronically authenticated by the government's Invoice Registration Portal (IRP) before being shared with the buyer. It is NOT about generating invoices on a government portal — businesses continue to create invoices using their own software, but each invoice must be registered on the IRP to get an Invoice Reference Number (IRN) and a digitally signed QR code.

The e-invoicing system was introduced in phases starting October 2020 for businesses with turnover above Rs 500 Crore. The threshold has been progressively reduced, and as of 2026, it applies to businesses with aggregate turnover exceeding Rs 5 Crore in any financial year from 2017-18 onwards.

The primary objectives of e-invoicing are: eliminating fake invoices and bogus ITC claims, enabling real-time tax reporting, auto-populating GSTR-1 and e-way bills, and creating a standardized invoice format across all businesses.

Who Needs to Generate E-Invoices?

Exclusions: The following are exempt from e-invoicing even if turnover exceeds the threshold: SEZ units, insurance companies, banking companies, financial institutions, NBFCs, GTA (Goods Transport Agencies), passenger transport services, and cinema ticket sales (multiplex).

Important: The Rs 5 Crore threshold is checked across any financial year from 2017-18 onwards. Once your turnover exceeds Rs 5 Crore in any year, you must comply with e-invoicing for all subsequent years, even if current year turnover drops below the threshold.

How E-Invoicing Works — Step by Step

1. Generate invoice in your software: Create the B2B invoice using your regular billing/ERP software. The invoice must include all mandatory fields as per the e-invoice schema (version 1.01 or later).
2. Convert to JSON format: Your software converts the invoice data into the prescribed JSON format. Most accounting software (Tally, Zoho, ClearTax, etc.) do this automatically.
3. Upload to IRP: The JSON file is transmitted to the Invoice Registration Portal via API. The IRP validates the invoice data (GSTIN, HSN codes, tax calculations, etc.).
4. IRP generates IRN: If validation passes, the IRP generates a unique 64-character Invoice Reference Number (IRN) using a hash of GSTIN + invoice number + financial year.
5. Digital signature and QR code: The IRP digitally signs the invoice and generates a QR code containing key invoice details (GSTIN, IRN, invoice value, number of items, etc.).
6. Signed invoice returned: The digitally signed JSON with IRN and QR code is returned to the supplier. The supplier then shares the e-invoice (with QR code) with the buyer.
7. Auto-population: The e-invoice data is auto-populated in the supplier's GSTR-1 and the buyer's GSTR-2B. If an e-way bill is required, it is also auto-generated.

E-Invoice JSON Format and Mandatory Fields

The e-invoice JSON schema includes several mandatory fields that must be present in every invoice:

HSN code requirements: For businesses with turnover above Rs 5 Crore, 6-digit HSN codes are mandatory on all invoices. For turnover between Rs 1.5 Crore and Rs 5 Crore, 4-digit HSN codes are required.

Penalties for Non-Compliance

Non-compliance with e-invoicing requirements can result in significant penalties and operational disruptions:

• Invoice treated as invalid: A B2B invoice issued without IRN by an applicable taxpayer is considered invalid under GST law. The buyer cannot claim ITC on such invoices.
• Penalty under Section 122: Issuing invoices without e-invoice compliance attracts a penalty of Rs 10,000 or the tax amount involved, whichever is higher, for each invoice.
• ITC denial to buyer: The buyer who receives a non-compliant invoice (without IRN) cannot claim Input Tax Credit. This creates pressure from buyers to comply.
• E-way bill issues: Without a valid IRN, e-way bills cannot be auto-generated. Goods in transit without a valid e-way bill attract penalties and possible detention.
• GSTR-1 auto-population fails: Non-compliant invoices are not auto-populated in GSTR-1, creating reconciliation issues and potential interest on late filing.

Time limit for IRN generation: As per recent notifications, the IRN must be generated within 30 days of the invoice date for businesses with turnover above Rs 100 Crore. For others, there is currently no strict time limit, but generating IRN at the time of invoice creation is recommended.

How to Implement E-Invoicing

If your business needs to comply with e-invoicing, here are the practical steps to implement it:

1. Check applicability: Verify if your aggregate turnover in any year from 2017-18 onwards exceeds Rs 5 Crore. If yes, e-invoicing is mandatory.
2. Update your software: Ensure your billing/ERP software supports e-invoice generation. Most popular software (Tally Prime, Zoho Books, ClearTax, myBillBook) already supports it. Update to the latest version.
3. Register on IRP: Create an account on the e-Invoice portal (einvoice1.gst.gov.in). Generate API credentials for automated IRN generation from your software.
4. Validate your master data: Ensure all customer GSTINs, HSN/SAC codes, and item details are accurate. Invalid data will cause IRP validation failures.
5. Test with sandbox: Use the IRP sandbox environment to test your integration before going live. Generate test IRNs to verify the flow works correctly.
6. Go live: Start generating IRNs for all B2B invoices. Train your accounts team on the new process and error handling.
7. Monitor and reconcile: Regularly verify that all invoices have valid IRNs and are auto-populated in GSTR-1. Address any failures promptly.