E-Invoice for Solar Business: When It Applies and How to Issue

A Rajkot EPC closes the year at ₹4.7 crore. The accountant says, "Next year we may need e-invoicing." The owner asks the two questions every solar owner asks: does it apply to our home rooftop customers, and what happens if we get it wrong? (Illustrative.)

The answers are shorter than most forum threads suggest. The duty switches on at a turnover limit. It covers only some of your invoices. From a higher turnover it comes with a clock. Most of the confusion comes from mixing those three things.

Every figure below carries its source. We opened the CBIC notifications, the GSTN e-invoice portal FAQ and the Finance Ministry release on the 57th GST Council meeting (8 October 2026) on 31 October 2026. The GST portal's advisory page blocks automated access, and we say so where it matters.

This is a working guide, not tax advice. Your CA decides how the rules apply to your PAN and your contracts. Quickest Solar CRM does not issue e-invoices or GST invoices, and a quotation is not a tax invoice.

The Gate, Door and Clock Check for solar invoices

Three questions, asked in order, settle almost every e-invoice doubt a solar EPC has. We call this the Gate, Door and Clock Check. The Gate decides whether the duty applies to your business at all. The Door decides, invoice by invoice, whether a document goes to the government portal. The Clock decides how late you are allowed to be.

1. 1

   Gate: is your PAN inside the e-invoice duty?

   Your aggregate turnover has exceeded ₹5 crore in any financial year since 2017-18, counted across all your GSTINs under one PAN. If not, you are outside the duty today. Check again at every year-end.

2. 2

   Door: does this document go to the portal?

   Only invoices, credit notes and debit notes to a GST-registered buyer (B2B, business to business), or for exports, go through. A sale to a household with no GSTIN does not. A quotation or proposal is not a tax invoice and never does.

3. 3

   Clock: how long do you have?

   From ₹10 crore of aggregate turnover, the portal rejects an invoice more than 30 days old. Below ₹10 crore, we found no such hard stop. Either way, the invoice is not valid until it has its IRN (Invoice Reference Number).

Gate: the ₹5 crore test and what counts toward it

E-invoicing is mandatory for a registered person whose aggregate annual turnover (AATO) exceeds ₹5 crore in any preceding financial year from 2017-18 onwards. The limit is set by Notification 10/2023-Central Tax (CBIC, 10 May 2023), in force from 1 August 2023. It amends the original e-invoice notification, 13/2020-Central Tax of 21 March 2020. "Exceeds" means exactly ₹5 crore does not trigger it. "Any preceding financial year" reads as though a later dip below ₹5 crore does not switch it off. Ask your CA to confirm that for your case. On 31 October 2026 we searched the CBIC tax portal's notification list for e-invoice notifications under the central tax series. 10/2023 is the latest we found; none after it changes the limit.

The figure is the GST definition. Under section 2(6) of the CGST Act, 2017, "aggregate turnover" adds up all taxable supplies, exempt supplies, exports and inter-State supplies of every person with the same PAN, on an all-India basis. The GSTN portal FAQ confirms the test is based on the PAN.

Source: section 2(6), CGST Act, 2017, as updated by CBIC to 1 January 2022 (opened 31 October 2026). Later amendments may differ.

The start date is the next 1 April. If your turnover crosses the limit during a year, the portal FAQ says e-invoicing becomes required from the beginning of the next financial year. A year that crosses ₹5 crore in February 2027 puts you under the duty from 1 April 2027.

Solar owners miss that household sales count. A worked example, illustrative and before GST:

Illustrative. Assumes one PAN, one financial year, no exempt supplies and no reverse-charge purchases.

This EPC is inside the Gate although 59% of its turnover is household sales. The duty then touches only the ₹2.30 crore of commercial and dealer invoices. The 140 home invoices stay on the normal GST invoice route.

How the limit fell to ₹5 crore, and whether it is moving

The limit has been cut five times since it started at ₹500 crore in October 2020, and the ₹5 crore step has stood since 1 August 2023. Each step is a one-line amendment to Notification 13/2020-Central Tax, read on the GST Council and CBIC sites.

Sources: notification PDFs on gstcouncil.gov.in and cbic-gst.gov.in, opened 31 October 2026. 70/2020-CT (30 Sep 2020) added exports and the words 'any preceding financial year from 2017-18'. 23/2021-CT (1 Jun 2021) excluded government departments and local authorities as suppliers.

As of 31 October 2026 we found no notification that lowers ₹5 crore. The GST Council's list of Central Tax notifications shows no e-invoice limit change after 10/2023, though the list we could read ends with 2025 items, and the CBIC notification index did not load. Treat this as "latest we could find", and check the e-invoice portal's notifications page before you rely on it.

The 57th GST Council met on 8 October 2026. Its press release (Ministry of Finance, PIB, 8 October 2026) recommends one e-invoice change: extending e-invoicing to domestic supplies you receive from an unregistered person under reverse charge, and to imports of services, for taxpayers at ₹5 crore and above. It proposes no change to the ₹5 crore limit or to B2C. A Council recommendation is not a notification, and the release gives no effective date. The same release approves in principle an optional annual-return scheme for taxpayers up to ₹5 crore who supply only to unregistered buyers, with no details yet.

Should you prepare before you cross the limit? Some of it is worth doing, some of it you cannot do.

Door: which solar invoices go to the portal

Only B2B invoices, supplies to SEZs, exports and the credit and debit notes tied to them go through the portal. The GSTN e-invoice FAQ lists the documents covered as invoices, credit notes and debit notes issued to a registered person or for exports. It adds: "Reporting B2C Invoices by notified persons is not applicable/allowed currently." The notification itself speaks of supplies "to a registered person" and, since 70/2020-CT, "for exports".

For a solar EPC the line is the buyer's GSTIN, not the type of building. A home with no GSTIN on the invoice is B2C. A housing society that gives you its GSTIN is a registered person. So is a factory, a school trust with a GSTIN, or another installer.

Sources: GSTN e-invoice portal FAQ (einvoice.gst.gov.in/faqs, checked 31 October 2026) and Notification 13/2020-CT as amended. The portal's own list of covered buyers is the final word; ask your CA about any case that is not in this table.

An EPC is not on the exempt list. The portal FAQ names the entities outside e-invoicing: SEZ units, insurers, banks and NBFCs, goods transport agencies, passenger transport suppliers, multiplex cinema operators and online information service providers. Notification 23/2021-CT adds government departments and local authorities. The FAQ says the exemption is "with respect to the entity". Contractors and installers do not appear.

You do not generate e-invoices for invoices you receive. Your supplier does that.

Clock: the 30-day reporting limit

From 1 April 2025, a taxpayer with aggregate turnover of ₹10 crore or more cannot report an invoice, credit note or debit note to the portal after 30 days from its date. GSTN Advisory No. 543 sets this limit. The advisory page itself is behind a captcha for automated readers, so we confirmed the rule on the e-invoice portal operator's notice, an IRP on a gst.gov.in address, which quotes the advisory. It gives the example that an invoice dated 1 April 2025 must be reported by 30 April 2025. After 30 days the portal restricts IRN generation and shows an error.

The limit began with the biggest taxpayers. The e-invoice portal's advisory text applied a 30-day window above ₹100 crore from 1 November 2023 and said there was "no such reporting restriction" below that "as of now". Advisory 543 lowered the line to ₹10 crore.

For an EPC between ₹5 crore and ₹10 crore we found no hard stop in the advisories we could read. That can change, and it is no licence to be late: the buyer cannot receive a valid invoice until the IRN exists, so your practical clock is the day you send it.

How to issue an e-invoice, step by step

You create the invoice in your own accounting or billing software, report its data to an Invoice Registration Portal (IRP), and issue it only after the portal returns an IRN and a QR code. The GSTN e-invoice FAQ (version 1.3, 11 November 2020) says registered persons "will continue to create their GST invoices on their own" systems. Six IRPs exist. Use any one, but do not report the same invoice to more than one.

1. 1

   Check the buyer data

   Both your GSTIN and the buyer's GSTIN must be active on the GST system on the date you report (portal FAQ). A wrong or inactive GSTIN means no IRN.

2. 2

   Prepare the invoice with a unique number

   The IRP builds the IRN from your GSTIN, invoice number, document type and financial year. A number already reported is rejected as a duplicate.

3. 3

   Pick a mode and register

   The portal says direct API access is for taxpayers above ₹100 crore turnover, or for ERPs and GST Suvidha Providers (GSPs). A smaller EPC therefore reports through billing software that is tied to a GSP, or uses the free offline utility the portal offers to entities with no ERP or billing software of their own. Register your GSTIN on the e-invoice portal and test on the sandbox first.

4. 4

   Report the invoice data

   The data goes in the standard format, FORM GST INV-01 (a JSON file). The IRP checks key fields and replies with a signed JSON.

5. 5

   Receive the IRN, acknowledgement number and QR code

   The IRN is a 64-character reference. The acknowledgement number is 15 digits and is only for reference. The QR code comes inside the signed JSON.

6. 6

   Issue the invoice with the QR code on it

   The portal FAQ says the QR code must be printed on the invoice itself, not on a separate sheet. Send the PDF only now. Under Rule 48(5), an invoice issued without following this route is not treated as an invoice.

After reporting, the data flows to the GST system and appears in your GSTR-1 and the buyer's return, per the portal FAQ. Where goods move, it can also support an e-way bill.

Corrections are strict. The portal FAQ says amendments are not possible on the IRP. You can cancel an IRN within 24 hours of reporting, but not if the linked e-way bill is active or has been verified in transit. A cancelled invoice number cannot be used again. After 24 hours, the fix goes through GSTR-1 or the normal GST amendment route. That is why the data check in step 1 comes first. Our glossary entry on e-invoice defines the IRN and QR code in plain terms.

What a solar invoice must carry before you report it

Get the rate, the split and the codes right before the invoice goes to the portal, because you cannot edit it there afterwards. Four solar points to settle first.

The 5% rate on solar goods. The 56th GST Council cut the rate on renewable energy devices from 12% to 5%, effective 22 September 2025, as the Finance Ministry's FAQ of 3 September 2025 records. A billing template that still shows 12% prints a wrong invoice. Check the item master in your software.

The 70:30 split on a supply-and-install contract. The Explanation to entry 437 of Notification 9/2025 (Rate), in the CBIC-hosted copy of the Integrated Tax (Rate) notification, deems 70% of the gross consideration to be the value of the goods and 30% the value of the installation service, where one supplier supplies both under one contract. The goods leg carries the 5% rate. For the 30% service leg, the entry is serial number 38 of Notification 11/2017-Central Tax (Rate), which covers "construction or engineering or installation or other technical services" for setting up solar power based devices and solar power generating systems. Its rate column reads 9 for central tax (Notification 27/2018-Central Tax (Rate), 31 December 2018, in force 1 January 2019). The matching integrated tax entry reads 18 (Notification 28/2018-Integrated Tax (Rate)) and the Union Territory tax entry reads 9 (Notification 27/2018-Union Territory Tax (Rate)). Notification 15/2025-Central Tax (Rate) of 17 September 2025 changed only the Explanation against that entry, so that it is read with serial number 437 of Notification 9/2025; it did not touch the rate column, and nor did 15/2025-Integrated Tax (Rate). We opened these on the CBIC tax portal on 31 October 2026 and found no later notification amending the rate column. State tax comes from each State's own notification, which we did not open, so take the full intra-State rate from your CA or the GST rate finder. How the two legs appear on the invoice is a decision for you and your CA, and it must be made before you report. Our guides on GST on solar systems and GST on solar installation services discuss the service portion.

HSN on the goods lines and SAC on the service lines. Panels, inverters, batteries, structures and cables each have a heading. Installation and AMC are services with their own codes. See HSN codes for solar panels and SAC codes for solar installation, and the glossary on HSN code.

Discounts written on the invoice. Under section 15(3)(a) of the CGST Act, a discount given before or at the time of supply is left out of the value of supply only if it is duly recorded in the invoice. A discount given later needs an agreement made at or before the supply, linked to specific invoices, and the buyer must reverse the related input tax credit (section 15(3)(b)). A rep's side promise that is not on the invoice therefore does not reduce the taxable value. Our guide on solar discount approval covers it.

A quotation is not a tax invoice: what to capture at quote stage

A quotation or proposal offers a price. A tax invoice, under section 31 of the CGST Act, is the document a registered supplier issues showing the description, value and tax charged on a supply. Only invoices, credit notes and debit notes carry an IRN. Nothing you send before the sale does.

That makes the quote stage the cheapest place to prevent e-invoice errors. The portal rejects bad buyer data, and the IRN cannot be edited later. Whatever tool you quote in, capture these fields once, at quote stage, and carry them to the invoice.

Process list for any CRM, spreadsheet or quoting tool. It does not claim that a quoting tool issues invoices.

Put one line in your terms so nobody mistakes the quote for the bill. A sample you can adapt:

This quotation is not a tax invoice. A GST invoice, with an IRN and QR code where the law requires, is issued on [event] to the GSTIN given by the buyer in writing. Please send the buyer's GSTIN and billing address before work begins.

Keep the milestone events in that clause the same as the events in your payment schedule. Our guide on payment terms for solar customers shows how to peg each instalment to a proof, and the sales-to-installation handover SOP shows who owns the buyer data after signing. Our post on why solar quotes differ covers the line items a customer compares, including GST.

Five ways an e-invoice fails, and the fix

Most failures come from data that was wrong before the report, and from timing. The table below uses the portal FAQ and advisories.

Sources: GSTN e-invoice portal FAQ and advisories; IRP operator notice on the 30-day limit; all checked 31 October 2026.

The last row is the expensive one. The buyer's input tax credit under section 16(2)(a) needs "a tax invoice or debit note issued by a supplier registered under this Act". If your document is not treated as an invoice, the buyer has a credit problem and you have a customer to placate. Section 122(1)(i) of the CGST Act separately provides a penalty of ₹10,000 or the tax evaded, whichever is higher, for supplying without issuing an invoice or issuing an incorrect one (CBIC copy updated to 1 January 2022). How that applies to a missing IRN is a question for your CA, not a rule we can state.

How QuickEstimate fits

Quickest Solar CRM sits before the invoice, and we want to be exact about where it stops. It does not issue e-invoices or GST invoices. Your accounting or billing software does that, and the IRN comes from the portal. What the app does is the pre-sale work this guide says should be clean before an invoice is raised.

• Quotation system: build a proposal template with your logo, items, product photos and terms and conditions, so the line "this quotation is not a tax invoice" and your buyer-data request travel with every quote.
• Admin-set price list with margin: reps quote from one price list, so the figures that reach your accountant start from the same source.
• PM Surya Ghar subsidy in the proposal and PDF sharing on WhatsApp: the buyer sees the full price and the subsidy in one document, and the same chat is where you ask for the GSTIN in writing.

To see these on a real quote, book a demo. The Free plan gives 1 user and 10 proposals a month with no card, and Pro is ₹6,999 per user per year with a 3-user minimum, billed yearly with a GST invoice. Nothing in the app replaces your CA or your billing software.

What to do before your next year-end

1. Find your number. Ask your accountant for aggregate turnover by PAN for every year since 2017-18, from your GST returns. Include household sales. Write it down against the ₹5 crore line.
2. Split your invoices by buyer. Count how many of last year's invoices had a buyer GSTIN. Those are the invoices that would have gone to the portal.
3. Change the quote. Add a buyer-GSTIN and billing-address request, and the "not a tax invoice" line, to your quote template this week.
4. Ask your CA three things. How the 70:30 split should appear on your invoices, who generates the IRN (you or a software provider), and whether the 30-day limit will apply at your turnover.
5. Re-check the limit at year-end. Read the notifications page of the e-invoice portal on 31 March, not the forums.

Frequently asked questions

Is e-invoicing mandatory for a solar business?

Yes, once your PAN's aggregate turnover exceeds ₹5 crore in any financial year from 2017-18 (Notification 13/2020-CT as amended by 10/2023-CT, from 1 August 2023). The duty starts on the 1 April after the year you cross. Confirm your own position with your CA.

Do I need an e-invoice for rooftop solar sold to homeowners?

No. The GSTN portal FAQ says reporting B2C invoices is not applicable or allowed. A household with no GSTIN is B2C. The sale still counts toward your ₹5 crore aggregate turnover, and you still issue a normal GST invoice. If the buyer gives a valid GSTIN and you bill on it, the invoice is B2B and goes to the portal.

What is the e-invoice limit in 2026?

₹5 crore of aggregate turnover. As of 31 October 2026 we found no notification that changes it, and the 57th GST Council release of 8 October 2026 recommends no lower limit. It recommends extending e-invoicing to reverse-charge purchases from unregistered persons and to imports of services.

Does the 30-day reporting rule apply to my EPC?

If your aggregate turnover is ₹10 crore or more, yes. From 1 April 2025, under GSTN Advisory No. 543, the portal will not take an invoice, credit note or debit note more than 30 days after its date. Between ₹5 crore and ₹10 crore we found no such hard stop.

What happens if I issue an invoice without an IRN?

Under Rule 48(5), as quoted in the GSTN portal FAQ, an invoice that a notified person issues without following the portal route is not treated as an invoice. That can put your buyer's input credit at risk. Section 122(1)(i) of the CGST Act also provides a penalty for supplying without an invoice or issuing an incorrect one. Ask your CA how it applies.

Can I cancel or edit an e-invoice after it is reported?

You cannot edit it on the portal. You can cancel the IRN within 24 hours of reporting, unless the linked e-way bill is active or has been verified in transit. A cancelled invoice number cannot be reused. After 24 hours, the correction goes through your GSTR-1 or the normal GST amendment route.

Do quotations, proposals or advance receipts need an IRN?

A quotation or proposal is not a tax invoice, so it is not reported. The portal FAQ lists invoices, credit notes and debit notes as the covered documents. It does not list receipt vouchers for advances, so confirm that with your CA. Quickest Solar CRM prepares quotations and does not issue e-invoices or GST invoices.

Can a CRM or quoting tool issue an e-invoice for me?

An IRN comes only from an Invoice Registration Portal. Billing software reaches it through a GSP (direct API access is for taxpayers above ₹100 crore), or you reach it through the free offline utility on the portal. The invoice itself is created in your accounting or billing system. A CRM or quoting app that is not connected to the portal cannot obtain one. Quickest Solar CRM does not issue e-invoices or GST invoices from the app, so keep your billing software for that.