GST e-invoicing is a digital validation framework under which specified categories of B2B and export invoices must be electronically reported to, and authenticated by, a government-notified Invoice Registration Portal (IRP) before they can be validly issued to the recipient.
Core Framework, Technical Specifications, Implementation Architecture, and Compliance Rules
GST e-invoicing is a digital validation framework under which specified categories of B2B and export invoices must be electronically reported to, and authenticated by, a government-notified Invoice Registration Portal (IRP) before they can be validly issued to the recipient.
Introduced in a phased manner from 1 October 2020 for the largest taxpayers and progressively extended to smaller businesses, e-invoicing is governed by Rule 48(4) of the CGST Rules, 2017. Under this mandate, covered taxpayers report structural invoice data to the IRP, which validates the payload and returns a unique 64-character Invoice Reference Number (IRN) along with a digitally signed cryptographic QR code.
An invoice issued by a taxpayer covered under these provisions is not treated as a valid tax invoice under GST unless it carries this IRN and QR code. Issuing a covered invoice without a valid IRN renders the document completely invalid, severe penalties apply, and it jeopardises the recipient's ability to claim input tax credit on that supply.
Certain sectors remain exempt from the mandatory e-invoicing framework under Rule 48(4), regardless of their aggregate annual turnover:
Filing or pushing an invoice to the IRP depends on structural accounting elements aligned to the system validation engines.
| Category | Mandatory Structural Elements |
|---|---|
| 3.1 Supplier & Recipient Profiles |
• Supplier valid GSTIN profile, legal name, and physical office location pincode. • Recipient valid GSTIN profile, commercial legal name, billing destination, and delivery address. • Explicit State Code mapping to determine appropriate tax treatment (CGST/SGST vs. IGST). |
| 3.2 Invoice Metadata |
• Explicit Document Type code (INV for Invoice, CRN for Credit Note, DBN for Debit Note). • Unique, sequential alphanumeric invoice number matching the syntax rules of the GST portal. • Strict invoice issuance date string. |
| 3.3 Line Item Architecture |
• Description of goods/services alongside mandatory HSN codes (harmonized systemic structure). • Quantities, per-item units of measure, base prices, discounts, and taxable value totals. • Applicable GST tax slabs (0%, 5%, 12%, 18%, 28%) and exact matching figures for CGST, SGST, IGST, or Cess. |
| 3.4 Transport Identifiers (Optional for e-invoice; required for e-way bill) |
• Distance in kilometers (verified by portal auto-distance checker). • Transporter ID or specific vehicle registration string for active road delivery tracking. • Transport document references (Bill of Lading, Railway Receipt, or Airway Bill numbers). |
The taxpayer creates the standard billing record in their business ERP or accounting software. The application validates that all fields match the official JSON schema layout (Form GST INV-01).
The ERP system communicates with the Invoice Registration Portal (IRP)—either directly via secure API nodes, through a GSP connector, or via bulk offline JSON upload tools—to pass the invoice data.
The IRP runs deduplication algorithms to check for duplicate entries. It creates the unique 64-character IRN hash using the SHA-256 algorithm (built from Supplier GSTIN + Invoice Number + Financial Year), signs the invoice payload with the IRP’s private key, and generates a dynamic QR code.
The IRP passes the signed JSON data back to the taxpayer's ERP system. The ERP reads this data and automatically prints the secure QR code and IRN directly onto the physical invoice document sent to the customer. Concurrently, the portal shares this validated record with the core GST portal to update the supplier's GSTR-1 and the recipient's GSTR-2B log files.
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