Invoicing Under GST
Complete guide to GST-compliant invoicing, e-invoicing mandates, and the 30-day reporting rule for 2026.
GST Invoice Requirements
A GST invoice is the primary document evidencing the supply of goods or services. It serves as the foundation for claiming input tax credit and must contain specific mandatory fields as prescribed under GST law.
| Field | Requirement |
|---|---|
| Supplier's GSTIN | Mandatory for registered suppliers |
| Invoice Number | Unique, consecutive, max 16 characters |
| Invoice Date | Date of issuance |
| Recipient's GSTIN | Required for B2B supplies |
| Place of Supply | Determines tax type (CGST/SGST or IGST) |
| HSN/SAC Code | 2 digits for AATO < 5 Cr, 4 digits for AATO > 5 Cr |
| Taxable Value | Value after discount, excluding GST |
| GST Rate & Amount | CGST, SGST, IGST separately mentioned |
| Signature/Digital Signature | Required for authentication |
E-Invoicing Mandate (2026)
E-invoicing is mandatory for businesses with AATO exceeding ₹5 crore in any financial year since 2017-18. The system requires real-time reporting to the Invoice Registration Portal (IRP).
Who Must Comply?
- • Businesses with AATO > ₹5 crore
- • Government departments
- • SEZ units (for B2B supplies)
- • E-commerce operators (for B2B)
Documents Covered
- • Tax invoices (B2B)
- • Credit notes
- • Debit notes
- • Export invoices
🚨 30-Day Reporting Rule (AATO > ₹10 Cr)
Taxpayers with AATO of ₹10 crore or more must upload invoices to the IRP within exactly 30 days from the date of invoice generation. Any attempt to report beyond this window results in automated rejection, rendering the invoice legally invalid for GST purposes.
E-Invoicing Workflow
- 1Generate Invoice: Create invoice in ERP/billing software in prescribed JSON format
- 2Transmit to IRP: Send invoice data to Invoice Registration Portal via GSP/API
- 3Validation: IRP validates GSTINs, checks duplicates, and generates IRN
- 4IRN Generation: Invoice Reference Number (IRN) is generated as unique identifier
- 5QR Code & Signing: IRP digitally signs invoice and adds QR code
- 6Data Push: Data auto-populates to GSTR-1 and recipient's GSTR-2B
Invoice Reference Number (IRN)
The IRN is a unique 64-character hash generated by the IRP, comprising the supplier's GSTIN, invoice number, and financial year. It serves as the definitive identifier for each e-invoice.
IRN Components
- • Supplier GSTIN (15 characters)
- • Invoice number (max 16 characters)
- • Financial year (YYYY-YY format)
- • Hashed into 64-character alphanumeric string
Benefits of E-Invoicing
For Businesses
- • Eliminates manual data entry in GSTR-1
- • Auto-population of GSTR-2B for buyers
- • Reduced invoice reconciliation issues
- • Faster input tax credit claim
- • Reduced tax evasion and fake invoicing
- • Improved compliance rating
For Tax Administration
- • Real-time tracking of transactions
- • Reduced tax leakage
- • Better analytics and fraud detection
- • Streamlined audit and verification
- • Enhanced compliance monitoring
- • Efficient resource allocation
GST Suvidha Providers (GSP) & Application Service Providers (ASP)
GST Suvidha Providers (GSP)
GSPs are licensed by GSTN to provide direct API access to GST systems. They build their own software solutions integrated with GSTN.
- • Direct technical integration with IRP
- • Provide end-to-end e-invoicing solutions
- • Handle high-volume transactions
- • Examples: ClearTax, Cygnet, EY, PwC
Application Service Providers (ASP)
ASPs are software providers who enable e-invoicing through GSP infrastructure. They don't have direct GSTN integration but use GSP APIs.
- • Use GSP APIs for e-invoicing
- • Focus on user experience and additional features
- • Often cheaper than direct GSP solutions
- • Examples: Zoho Books, Tally, Busy
E-Invoice Cancellation & Amendment
Cancellation Rules
- • Can be cancelled within 24 hours on IRP
- • After 24 hours, cancel through GSTR-1
- • Once reported to GSTR-1, follow normal amendment process
- • Recipient should be informed of cancellation
- • Cancelled IRN cannot be reused
Amendment Process
- • E-invoice itself cannot be amended on IRP
- • Amendments done through GSTR-1
- • Changes reflect in next month's GSTR-2B for recipient
- • Original IRN remains unchanged
- • Credit/Debit notes can be issued for corrections
E-Invoice Technical Specifications
Schema Version
Current e-invoice schema is version 1.1. It defines the structure and data elements required for e-invoice generation and reporting.
Mandatory Fields
- • Document Type, Number, and Date
- • Supplier and Buyer GSTIN
- • Item details (description, HSN, quantity, value)
- • Tax details (CGST, SGST, IGST, Cess)
- • Total invoice value
- • Supply type (B2B, B2C, Export, SEZ)
QR Code Specifications
The QR code contains essential invoice details for quick verification:
- • GSTIN of supplier
- • GSTIN of recipient
- • Invoice number and date
- • Total invoice value
- • Number of line items
- • HSBN of main item
- • Validity of e-invoice
Common E-Invoicing Errors & Solutions
| Error | Cause | Solution |
|---|---|---|
| Duplicate IRN | Same invoice number already exists | Use unique invoice number or cancel previous |
| Invalid GSTIN | Wrong or inactive GSTIN | Verify GSTIN on portal before generating invoice |
| Schema Validation Failed | JSON doesn't match schema format | Validate JSON against e-invoice schema |
| Invalid HSN Code | HSN not found in master | Use correct 4/6/8 digit HSN from GST portal |
| 30-Day Violation | Invoice older than 30 days | Cannot report; declare in GSTR-1 directly |