E-Invoicing Under GST: Compliance Checklist for 2026

Turnover thresholds, IRN generation, QR codes, and penalties—everything your business needs to stay e-invoicing compliant.

Who Needs E-Invoicing?

As of 2026, businesses with aggregate turnover exceeding ₹5 crore in any financial year since 2017-18 must generate e-invoices via the IRP (Invoice Registration Portal). The threshold has been progressively lowered from ₹500 crore in 2020 and may drop further—possibly to ₹1 crore. Special categories like SEZ units, banking/insurance, and passenger transport have specific exemptions. Check your applicability carefully, considering all GSTINs under the same PAN.

How E-Invoicing Works

Generate your invoice in your billing system with all mandatory fields → convert to the prescribed JSON schema → push to one of the NIC's IRPs via API → receive back the IRN (Invoice Reference Number, a unique 64-character hash), digitally signed QR code, and the signed invoice JSON. The IRP simultaneously shares the data with the GST portal, auto-populating your GSTR-1 and your buyer's GSTR-2A/2B. This is not optional—it replaces the manual GSTR-1 upload for covered transactions.

Technical Implementation

Your billing software must support: GST e-invoice JSON schema v1.1+ (with all mandatory fields including HSN codes, tax rates, and place of supply), API integration with NIC's IRP (authentication via client ID/secret, API rate limits), QR code generation and embedding in the printed/PDF invoice, IRN storage and display, and handling of cancellations (within 24 hours) and amendments. Test thoroughly in the sandbox before going live.

Mandatory Fields & Common Mistakes

Every e-invoice must include: supplier GSTIN, buyer GSTIN (for B2B), document type and number, date, HSN/SAC codes (minimum 4 digits for turnover > ₹5 crore, 6 digits for > ₹20 crore), item-level details with quantity and unit, tax rates and amounts, and total invoice value. Common mistakes: wrong place-of-supply code (causes IGST vs CGST+SGST errors), missing HSN codes, invalid document number format, and GSTIN validation failures.

Credit/Debit Notes & Amendments

Credit and debit notes linked to e-invoiced transactions must also be reported through the IRP. Each gets its own IRN. The original invoice IRN must be referenced. Amendments to e-invoices can only be done through credit/debit notes—you cannot modify a submitted e-invoice. Cancellation is allowed within 24 hours of generation; after that, issue a credit note.

Multi-System Integration

Large enterprises often have multiple billing systems (retail POS, wholesale ERP, online marketplace, manual invoicing for exceptions). All must route through the IRP. Implement a centralised e-invoicing gateway that receives invoices from all sources, validates them, pushes to IRP, and distributes the signed response back to the originating system. This prevents the chaos of multiple direct integrations.

Penalties for Non-Compliance

Non-generation of e-invoice when required: penalty of 100% of tax due or ₹10,000, whichever is higher—per invoice. Your buyer may also be denied ITC on invoices without valid IRN. Additionally, your GSTR-1 won't be auto-populated, creating reconciliation nightmares. The cost of non-compliance—in penalties, buyer relationships, and operational chaos—far exceeds the one-time cost of implementation.

Implementation Checklist

(1) Confirm applicability (turnover threshold, entity type). (2) Register on the NIC e-invoice portal and obtain API credentials. (3) Update billing software to support the JSON schema. (4) Test in sandbox with all your document types (invoices, credit notes, debit notes). (5) Go live with a small batch and verify GSTR-1 auto-population. (6) Monitor daily: check for rejected IRNs and fix root causes. (7) Train your billing team on the new workflow and error handling.