E-Invoicing Under GST: Requirements, QR Codes & Implementation

A complete 10-minute guide to E-Invoicing under GST: turnover threshold rules, IRN generation, signed QR codes, cancellation rules, penalties, and automated implementation.

The implementation of Electronic Invoicing (E-Invoicing) by the Central Board of Indirect Taxes and Customs (CBIC) is one of the most transformative digital reforms in India's tax history. E-invoicing has fundamentally altered how businesses generate, validate, and store B2B sales invoices.

However, many business owners, finance heads, and accountants still struggle with key operational details: Who is required to generate e-invoices? What is the 24-hour cancellation rule? Why do buyers reject non-e-invoiced bills? How do IRN and signed QR codes work?

In this comprehensive 2026 guide, we cover everything you need to know about E-Invoicing under GST: turnover applicability, technical terminology, step-by-step workflow, GSTR-1 and E-Way bill auto-population, non-compliance penalties, and how to automate e-invoicing directly within your accounting software.

1. What is E-Invoicing under GST?

A common misconception among business owners is that e-invoicing means generating invoices directly on the GST portal. This is incorrect.

E-Invoicing (Electronic Invoicing) is a system where B2B invoices created in your accounting or ERP software are electronically submitted to a government-notified Invoice Registration Portal (IRP) for validation.

Upon submission, the IRP performs automated checks, digitally signs the payload, and generates:

A unique 64-character Invoice Reference Number (IRN).
A signed QR Code containing key invoice parameters.

Only after receiving the IRN and QR code back from the IRP is the invoice legally considered a valid GST Tax Invoice under Rule 48(4) of the CGST Rules.

2. Who Must Generate E-Invoices? (Applicability & Thresholds)

E-invoicing was introduced in phases based on Aggregate Annual Turnover (AATO) across all GSTINs associated with a single PAN in any preceding financial year from 2017-18 onwards.

Threshold Evolution Timeline:

Phase 1 (Oct 2020): Turnover > ₹500 Crore
Phase 2 (Jan 2021): Turnover > ₹100 Crore
Phase 3 (Apr 2021): Turnover > ₹50 Crore
Phase 4 (Apr 2022): Turnover > ₹20 Crore
Phase 5 (Oct 2022): Turnover > ₹10 Crore
Phase 6 (Aug 2023 onwards): Turnover > ₹5 Crore

⚠️ Critical Rule: If your aggregate business turnover exceeded ₹5 Crore in any financial year from 2017-18 to the present, e-invoicing is mandatory for all your B2B and export transactions!

Who is Exempt from E-Invoicing?

Regardless of turnover, the following entities and sectors are currently exempted from mandatory e-invoicing:

Insurers, Banking Companies, and Financial Institutions (including NBFCs).
Goods Transport Agencies (GTA) supplying road transport services.
Passenger Transport Service providers.
Admission service providers for Exhibition of Cinematograph Films in Multiplex Screens.
Special Economic Zone (SEZ) Units (Note: SEZ Developers are not exempt).
Government Departments and Local Authorities.

3. Documents & Transaction Types Covered

E-invoicing applies strictly to specific document types and commercial transactions:

Covered Document Types:

Tax Invoices (B2B sales)
Credit Notes (issued for B2B supplies)
Debit Notes (issued for B2B supplies)

Covered Transaction Types:

B2B Sales: Supplies to other registered GST taxpayers.
B2G Sales: Supplies to Government departments registered as taxpayers.
Exports: Direct Exports and Deemed Exports (with or without payment of IGST).
SEZ Supplies: Supplies made to SEZ units or SEZ developers.

NOT Covered:

B2C Sales: Sales to end consumers or unregistered buyers (covered under Dynamic B2C QR Code rules if turnover > ₹500 Cr).
Bill of Supply: Exempted or non-GST sales.
Inward Supplies: Self-invoices under Reverse Charge Mechanism (RCM).

4. Anatomy of an E-Invoice: IRN, QR Code, and Schema

An e-invoice contains three standardized technical components defined by the GST Council under schema INV-01:

1. Invoice Reference Number (IRN)

The IRN is a unique 64-character alphanumeric hash generated by the SHA-256 algorithm based on four parameters:

Supplier GSTIN
Financial Year (e.g., 2025-26)
Document Type (e.g., INV, CRN, DBN)
Document Number (e.g., INV-00124)

Example IRN:
3f8a9b2c1d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a

2. Signed QR Code

The IRP returns a digitally signed QR code that must be printed on the invoice PDF or physical invoice copy. It allows tax officers and buyers to verify invoice authenticity offline using a mobile app.

Contains: Supplier GSTIN, Recipient GSTIN, Invoice Number, Invoice Date, Total Taxable Value, Total Tax Amount, HSN count, and IRN.

3. Digital Signature

The JSON payload returned by the IRP contains the government's digital signature, confirming that the invoice data was validated and registered on the GST network.

5. Multiple IRP Portals & High Availability

To ensure zero downtime, the government has authorized multiple Invoice Registration Portals (IRPs) operated by different official agencies:

NIC IRP (e-Invoice Portal 1 & 2 operated by National Informatics Centre)
IRIS IRP (Operated by IRIS Business Services)
Cygnet IRP (Operated by Cygnet Infotech)
Clear IRP (Operated by Clear)
Master India IRP (Operated by Master India)

Modern accounting software uses GSP (GST Suvidha Provider) APIs to automatically failover between these portals if any single government server experiences slowdowns.

6. Dynamic B2C QR Codes vs. B2B E-Invoicing

It is important to distinguish between B2B E-Invoicing and Dynamic B2C QR Codes:

Parameter	B2B E-Invoicing (INV-01)	Dynamic B2C QR Code
Applicability	Turnover > ₹5 Crore	Turnover > ₹500 Crore
Target Audience	Sales to Registered GST Taxpayers (B2B)	Sales to Unregistered Consumers (B2C)
IRP Validation	Mandatory (Generates IRN & Government QR)	No IRP validation (Generates Payment UPI QR)
Purpose	Tax audit compliance & ITC tracking	Enabling digital payments (UPI/IMPS) for consumers

7. Step-by-Step E-Invoice Generation Flow

Here is how the end-to-end e-invoicing workflow operates in practice:

  Step 1: Create B2B Sales Invoice in Accounting Software (ForkOST)
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  Step 2: Software validates JSON schema & sends payload to IRP API
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  Step 3: IRP checks duplicate IRN & validates buyer GSTIN
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  Step 4: IRP generates 64-char IRN, signs payload & creates QR Code
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  Step 5: Software receives signed payload, prints QR code on PDF,
          and auto-populates E-Way Bill & GSTR-1 Table 4A

8. Automatic Sync with GSTR-1 and E-Way Bill

One of the greatest benefits of e-invoicing is the elimination of duplicate data entry:

1. GSTR-1 Auto-Population

Once an IRN is generated on the IRP, the invoice details automatically flow into your GSTR-1 Table 4A/4B (B2B Supplies). When you file GSTR-1 at the end of the month, these entries are pre-filled, reducing manual errors.

2. E-Way Bill Generation (Part A & Part B)

If your invoice involves the movement of goods exceeding ₹50,000, you can request the IRP to generate both the IRN and E-Way Bill simultaneously by including transporter details (Vehicle Number or Transporter ID) in the e-invoice JSON payload.

9. Cancellation and Amendment Rules for E-Invoices

Managing modifications or cancellations of e-invoices follows strict regulatory constraints:

The 24-Hour Cancellation Window

An e-invoice (IRN) can be cancelled on the IRP only within 24 hours of generation.
Condition: An IRN cannot be cancelled if an active E-Way Bill attached to it is currently in transit. The E-Way Bill must be cancelled first before cancelling the IRN.
No Partial Cancellation: You cannot partially cancel an e-invoice; the entire IRN must be cancelled.

What Happens After 24 Hours?

If 24 hours have passed since IRN generation, the IRP blocks cancellation. To correct errors after 24 hours:

Do NOT attempt to re-generate an e-invoice with the same invoice number.
Issue a Credit Note (with its own e-invoice IRN) to nullify the original sale.
Manually amend or delete the auto-populated row in your GSTR-1 prior to monthly filing.

10. Penalties and Consequences of Non-Compliance

Failing to generate an e-invoice when required carries severe financial and commercial consequences:

1. Financial Penalties (Section 122 & 125)

Penalty for Non-Issuance of E-Invoice: ₹10,000 per invoice OR 100% of the tax amount due, whichever is higher.
Penalty for Incorrect Invoicing: ₹25,000 per invoice for issuing an invoice without a valid QR code or IRN.

2. Loss of Buyer Credit (The Buyer Risk)

Under GST law, an invoice issued by an applicable seller without an IRN and signed QR code is considered legally invalid.

Buyers cannot claim Input Tax Credit (ITC) on invalid non-e-invoiced bills.
Corporate buyers will routinely hold payments or reject invoices from vendors who fail to provide valid e-invoices with scannable QR codes.

11. Automating E-Invoicing with ForkOST

Navigating portal credentials, JSON payloads, and IRP downtime manually is complex.

ForkOST makes e-invoicing completely frictionless:

1-Click IRN Generation: Generate IRN and signed QR code directly from your sales invoice screen in under 2 seconds.
Combined E-Invoice & E-Way Bill: Generate both IRN and E-Way Bill in a single click for transport deliveries.
Automatic QR Code Printing: Prints clear, scannable QR codes on your customized invoice PDFs.
Real-Time Validation: Validates GSTIN, HSN codes, and PIN codes before submitting payload to prevent IRP rejections.

12. Frequently Asked Questions (FAQ)

Q1: Is e-invoicing required for B2C sales to end consumers?

No. Standard e-invoicing (IRN generation via IRP) applies only to B2B, B2G, and Export transactions. However, taxpayers with turnover exceeding ₹500 Crore must display a dynamic B2C QR code for payment processing.

Q2: Can the same invoice number be re-used after cancelling an IRN?

No. Once an IRN is generated for an invoice number (e.g., INV-2026-001), the GST portal stores that invoice number permanently. Even if you cancel the IRN within 24 hours, you cannot reuse INV-2026-002. You must issue a new invoice number (e.g., INV-2026-002).

Q3: Are export invoices required to have an e-invoice IRN?

Yes. All direct exports (with or without payment of tax), deemed exports, and supplies to SEZ units/developers require mandatory e-invoicing if your turnover exceeds ₹5 Crore.

Q4: Is a physical signature still required on an e-invoice?

No. Under Rule 46 of CGST Rules, if an invoice contains a government-signed QR code and digital signature from an authorized IRP, a physical or manual signature is not required.

13. Conclusion

E-invoicing is no longer optional for growing Indian businesses. By automating IRN and QR code generation, you eliminate compliance risks, speed up customer invoice approvals, and ensure your buyers receive their Input Tax Credit on time.

👉 Start your free trial with ForkOST — 1-click E-Invoicing, E-Way Bills, automated GSTR-1, and seamless inventory management.
👉 Master E-Invoicing Rules at ForkOST Academy — practical, hands-on training in GST compliance and billing software.

E-Invoicing Under GST: Requirements, QR Codes, and Implementation (2026)