What is an e-Invoice?
An e-Invoice under Indian GST is a digitally generated tax invoice that has been reported to and authenticated by the GST Network's Invoice Registration Portal (IRP). The IRP validates the invoice structure, assigns a unique 64-character Invoice Reference Number (IRN), generates a QR code embedding key invoice details, and transmits the data to the GST and e-Way Bill systems.
The mandate has been rolled out progressively. e-Invoicing began in October 2020 for businesses above INR 500 crore turnover and has been extended to lower thresholds in steps. From 1 August 2023 (notification 10/2023-CT), businesses with annual aggregate turnover above INR 5 crore in any preceding financial year since 2017-18 must comply. Businesses below the threshold are not enabled on the portal. From 1 April 2025, businesses with turnover of INR 10 crore or more must also report each invoice within 30 days of its date (GSTN Advisory No. 543).
e-Invoice does not replace the tax invoice; it IS the tax invoice with the additional IRN and QR code printed. The invoice still contains all standard elements (GSTIN, correct HSN classification for panels and inverters, taxable value, tax rates, total). Customers verify the IRN by scanning the QR code or looking up on the IRP portal.
Why e-Invoice matters for solar EPCs
An EPC above INR 5 crore of aggregate turnover is within the e-Invoicing mandate, layered on top of existing GST obligations on solar system sales. An invoice without an IRN is not treated as an invoice, which puts the buyer's ITC claim at risk and can lead to a section 122 penalty (INR 10,000 or the tax evaded, whichever is higher). Residential B2C sales are outside e-Invoicing, so the obligation mostly touches commercial and industrial B2B work.
For accounting and compliance teams, e-Invoicing changes the invoice workflow. The invoice cannot be edited after IRN is generated (only cancelled within 24 hours or replaced by credit/debit note). This forces stricter pre-invoice validation discipline. Quality EPCs build invoice approval workflows before IRN generation.
The e-Way Bill link is a benefit: invoice details from the IRN can be reused for the e-Way Bill, reducing duplicate entry. EPCs shipping modules and inverters frequently benefit from this integration, especially given how the different GST rates on modules, inverters and structures add complexity to line-item tax calculation on the invoice.
How e-Invoicing works end-to-end
- Invoice creation. EPC generates invoice in accounting or CRM software.
- JSON conversion. Software converts to standard e-Invoice JSON schema.
- Upload to IRP. JSON sent to an IRP (for example einvoice1.gst.gov.in) by API, or through the portal or the free offline utility. Report each invoice on one IRP only.
- Validation. IRP validates GSTIN, HSN, structure.
- IRN and QR code generation. Returned to EPC software.
- Final invoice issued. With IRN and QR code printed.
- GSTR-1 auto-population. Data flows to GST returns.
- e-Way Bill. Invoice details can be reused, reducing duplicate entry.
- Buyer verification. Scan QR or lookup IRN.
- ITC claim. Buyer claims based on authenticated invoice.
Benefits of e-Invoicing
- GST compliance. Mandatory above threshold.
- Buyer ITC enablement. Authenticated invoices.
- GSTR-1 auto-fill. Reduces return preparation effort.
- e-Way Bill link. Less duplicate entry.
- Audit trail. Immutable IRN-linked record.
- Fraud reduction. Standardised, validated invoices.
- Buyer trust. QR code verification.
Limitations and challenges
Software dependency. Requires e-Invoice-capable accounting or ERP software or the free offline utility; EPCs still running invoicing off spreadsheets face the same fragility described in the Excel tax on solar businesses.
Pre-invoice discipline. Cannot edit after IRN.
24-hour cancellation window. Beyond that, changes go through GSTR-1 and credit or debit notes.
API uptime. IRP downtime stalls invoicing.
Threshold timing. If you cross INR 5 crore during a year, e-Invoicing applies from the beginning of the next financial year.
30-day reporting limit. From 1 April 2025, businesses with turnover of INR 10 crore or more cannot report an invoice older than 30 days.
e-Invoicing across solar EPC operations
| Activity | e-Invoice applicability |
|---|---|
| Sale of solar plant to a GST-registered commercial customer | Required if EPC above threshold |
| Sale to residential B2C customer | Not reported on the IRP (B2C) |
| Sale to SEZ unit | Required |
| Export of solar equipment | Required |
| RCM purchases from unregistered suppliers | Not required today; extension recommended by GST Council on 8 Oct 2026, not yet notified |
| Credit and debit notes | Required |
Quick facts
| Current threshold | INR 5 crore aggregate turnover (CBIC 10/2023-CT, from 1 Aug 2023) |
|---|---|
| Reporting time limit | 30 days for turnover of INR 10 crore or more, from 1 Apr 2025 (Advisory No. 543) |
| Portal | einvoice1.gst.gov.in |
| Key identifier | IRN (64-character alphanumeric) |
| Penalty (s.122(1)(i) CGST) | INR 10,000 or tax evaded, whichever is higher |
| Cancellation window | 24 hours |
| Data flows to | GST systems; reusable for the e-Way Bill |
| Not covered | B2C, exempt supplies, SEZ units, insurers, banks and NBFCs, GTA, passenger transport |
Common mistakes about e-Invoicing
- Missing threshold crossing. The obligation starts from the beginning of the next financial year.
- Editing post-IRN. Not allowed.
- Cancellation past 24 hours. Not possible on the IRP; use a credit note or GSTR-1 amendment.
- Re-keying invoice data into the e-Way Bill. Wastes the IRN link.
- Skipping QR code on printed invoice. Buyer verification fails.
- Wrong HSN code in JSON. Validation rejection.
- Reporting an invoice late. Past 30 days the IRP rejects it for turnover of INR 10 crore or more.
- No backup workflow during IRP downtime. Invoice queue stalls.
Key takeaways
- e-Invoice is the IRN-authenticated tax invoice under GST.
- Mandatory for businesses above INR 5 crore aggregate turnover (10/2023-CT).
- IRP assigns unique IRN and QR code.
- Invoice data flows to the GST systems and can be reused for the e-Way Bill.
- Cannot edit post-IRN; 24-hour cancellation window.
- No IRN means the invoice is not valid; section 122 penalty is INR 10,000 or tax evaded, whichever is higher.
- Use e-Invoice-capable accounting software or the free GSTN offline utility.
Frequently Asked Questions
What is an e-Invoice?
An e-Invoice is a digitally generated invoice that has been reported to and authenticated by the GST Network's Invoice Registration Portal (IRP), which assigns a unique Invoice Reference Number (IRN) and a QR code. Under Indian GST, e-Invoicing is mandatory for taxpayers above specified turnover thresholds. The threshold is INR 5 crore annual aggregate turnover (CBIC notification 10/2023-CT, from 1 August 2023); we found no later change in the official notification list as checked on 31 October 2026.
Who must generate e-Invoices?
All GST-registered businesses with annual aggregate turnover above INR 5 crore in any preceding financial year since 2017-18. The threshold was lowered in steps from INR 500 crore (October 2020) to INR 5 crore (August 2023). Businesses below INR 5 crore are not covered and cannot report on the IRP.
Do solar EPCs need e-Invoicing?
Yes, if the EPC's aggregate turnover (on the same PAN) exceeded INR 5 crore in any financial year from 2017-18 onwards, for B2B supplies, supplies to SEZ units, deemed exports and exports. An EPC below the threshold is not covered, and the e-Invoice portal says the facility is not voluntary: only notified businesses are enabled. If you cross the limit during a financial year, the requirement starts from the beginning of the next financial year.
How does e-Invoicing work?
EPC generates invoice in accounting software in standard JSON format, uploads to IRP via API or portal, IRP validates and assigns IRN plus QR code, EPC issues final invoice to customer with IRN and QR code, IRP returns the signed e-invoice with IRN and QR code, and the data flows on to the GST systems. The QR code must be printed on the invoice.
What is the IRN?
Invoice Reference Number is the unique 64-character alphanumeric identifier assigned by IRP to each authenticated e-Invoice. IRN proves the invoice has been reported. Buyers verify IRN via QR scan or portal lookup before accepting invoice.
What documents require e-Invoicing?
Invoices, credit notes and debit notes issued to registered persons (B2B), and supplies to SEZ units, deemed exports and exports. B2C invoices are not reported on the IRP at present. For purchases from unregistered suppliers under reverse charge (RCM) and imports of services, e-Invoicing does not arise today; the GST Council on 8 October 2026 recommended extending it to these for businesses with turnover of INR 5 crore and above, but a recommendation is not a notification and no effective date was given.
What documents are exempt from e-Invoicing?
B2C supplies, and supplies that are nil-rated or wholly exempt (a bill of supply is issued, not a tax invoice). Certain entities are exempt as suppliers: SEZ units, insurers, banks and financial institutions including NBFCs, goods transport agencies, passenger transport suppliers, multiplex cinema admissions and OIDAR services. Check the current list on the e-Invoice portal FAQ.
What happens if e-Invoicing is missed?
Under Rule 48(5) of the CGST Rules, an invoice issued by a notified business in any other way than through the IRP is not treated as an invoice; it becomes valid only with an IRN. Supplying without a proper invoice can attract a penalty under section 122(1)(i) of the CGST Act of INR 10,000 or the tax evaded, whichever is higher, and the buyer's ITC claim needs a valid tax invoice (section 16(2)(a)). Separately, businesses with aggregate turnover of INR 10 crore or more must report an invoice within 30 days of its date from 1 April 2025 (GSTN Advisory No. 543), and the IRP rejects older invoices.
What is the relationship between e-Invoice and e-Way Bill?
Once an invoice has its IRN, its details can be used to generate the e-Way Bill, so you do not have to key the invoice details again; you add the vehicle and transport details (Part B). An e-invoice cannot be cancelled on the IRP once an e-Way Bill is active or has been verified.
Does e-Invoice replace tax invoice?
No. e-Invoice IS the tax invoice plus IRN and QR code. The invoice issued to customer still contains all standard tax invoice elements (GSTIN, HSN, taxable value, tax rates, total) with the additional IRN and QR code.
What is the IRN validation lifecycle?
Once IRN is generated, the invoice cannot be modified. Errors require credit/debit note or cancellation within 24 hours. After 24 hours, cancellation is not possible. Quality EPCs validate invoices before IRN generation.
What software supports e-Invoicing for EPCs?
Many accounting and ERP packages (for example Tally Prime, Zoho Books, Marg) offer e-Invoice reporting; check that the version you use does and that it prints the QR code. Quickest Solar CRM does not issue e-invoices, so keep invoicing in your accounting software. Businesses without an ERP can use the free offline utility from GSTN, or the portal, to prepare and upload invoices.
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- GSTN e-Invoice portal. Official documentation. einvoice1.gst.gov.in
- CGST Rule 48 and Notifications. e-Invoicing mandate and threshold. cbic.gov.in
- CBIC Notification 10/2023-Central Tax (10 May 2023). Threshold of INR 5 crore from 1 August 2023. gstcouncil.gov.in
- GSTN Advisory No. 543. 30-day reporting limit for turnover of INR 10 crore or more, from 1 April 2025.
- CGST Act, 2017. Sections 16(2)(a), 31 and 122(1)(i).
- GST Council 57th meeting press release (PIB, 8 October 2026). Recommendation on RCM and import of services.
- NIC technical specifications. JSON schema and APIs.
Written by Parth Maru, Sales & Operations Lead, Quickest Solar CRM (Surat).
Last updated: 14 October 2026.