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Solar installers

GST billing software for solar installers and EPC companies

Price a 3 kW or a 10 kW rooftop system once, turn the accepted quotation into a GST invoice with HSN and SAC on each line, and collect the instalments against it.

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In short

SimpleERP is billing software for rooftop solar installers in India. A quotation priced by kW becomes a GST invoice carrying panels and inverters under HSN codes and installation under SAC 9954, with each instalment recorded against the homeowner's balance.

Illustration of the keyboard-first invoice editor with a focused line, live tax totals and shortcut hints.

A GST billing day at Marudhar Solar Energy

Marudhar Solar Energy in Jaipur commissions four to six rooftop systems a week, mostly 3 kW and 5 kW homes in Mansarovar and Vaishali Nagar, plus the odd 20 kW school or cold store. Every job starts as a quotation after the site survey, and the price changes twice before the homeowner signs.

Money arrives in three moments: an advance of 30 percent when the panels are ordered, the main GST invoice once the structure and inverter are up, and the final payment after the discom fits the net meter. The accountant used to type the same panel wattage, inverter model and kW rating into three different Excel sheets.

In SimpleERP the quotation, the invoice and the payments form one chain. The invoice copies the quotation's lines, each receipt is recorded against that invoice, and the homeowner's balance is one click away from the customer's name.

How does a rooftop quotation become a GST invoice?

Build the quotation from your own products and services: modules, inverter, mounting structures, DC cable by the metre and installation. When the homeowner says yes, convert it, and every line arrives on the invoice with its quantity, rate, HSN or SAC and tax.

  • Copy last week's 5 kW quotation for a new homeowner and change only the name and the roof notes.
  • A valid-until date on the quotation, so a price given before a module price rise is not honoured months later.
  • Revisions are saved as new drafts, so the first price you gave stays on file if a customer disputes it.
  • Invoice numbers follow the April to March year, such as INV-2026-27-0148, inside the 16-character GST limit.

Illustration of GST tax invoice INV-2026-27-0213 to Ravi Stores with CGST 9% and SGST 9%, round off, a UPI QR code and the amount in words.

A 5 kW rooftop invoice converted from the accepted quotation.

Which HSN and SAC codes go on a solar invoice?

A typical rooftop bill mixes four or five codes. These are the ones Marudhar Solar Energy uses most; each line in SimpleERP keeps its own code and rate, and the HSN summary at the foot of the print groups them for GSTR-1.

  • The rate sits on the product, so whoever bills never picks a GST rate from memory.
  • Change a product's rate once and new invoices use it; posted invoices keep the rate they were billed at.
Invoice lineHSN or SACUsual GST, to confirm
Solar PV modules (panels), 540 WpHSN 8541Revised in September 2025
Grid-tie inverter, 5 kWHSN 8504Revised in September 2025
GI mounting structuresHSN 7308Commonly 18%
DC and AC cable, per metreHSN 8544Commonly 18%
Installation and commissioningSAC 9954Depends on how the contract is split
Codes and rates as a starting point for a rooftop invoice. Rates change, so confirm the rate for your goods with your CA or the GST portal before you rely on it.

What changes when the roof is in another state?

Marudhar Solar Energy is registered in Rajasthan with state code 08. A home in Jaipur is billed CGST and SGST; a factory roof across the border in Haryana is billed IGST. SimpleERP reads the customer's state from the GSTIN or address and picks the split before you save.

  • Unregistered homeowners are billed with a name, phone number and address, no GSTIN needed.
  • A housing society with a GSTIN has its number checked as you type and printed on the invoice.
  • One place of supply per invoice, so IGST and CGST plus SGST never sit on the same bill.

How do you track the advance and the payment after net metering?

Rooftop customers rarely pay in one go. Record the advance as money on account, apply it when the invoice posts, and the invoice shows partially paid until the last instalment clears.

  • UPI QR on the printed invoice for a homeowner who wants to pay while the crew is still on the terrace.
  • Receivables ageing separates homeowners waiting on a net meter from those who are simply late.
  • A credit note handles a returned panel or a discount agreed after the bill.

One system

Where solar billing connects

The invoice that bills the panels also takes them out of the godown, posts the sale and GST, and adds the balance to the homeowner's account.

Honest limits

What SimpleERP does not do yet

  • E-invoice IRN and QR code, and e-way bills, are not generated through the government APIs
  • Cess is not calculated; GST return filing stays with you or your accountant
  • No price lists: every line is priced as you bill it
  • No link to the rooftop subsidy portal: subsidy applications and discom paperwork are filed there separately
  • No serial number field for panels or inverters; type them into the line description if the homeowner needs them for warranty

Getting started

Start with GST billing

  1. Sign up with your phone

    Name, phone number and a password. No card for the seven-day trial, and email is optional.

  2. Tell us about the business

    Type your GSTIN and the state fills itself. Accounts, GST rates, units, roles and numbering are seeded for you.

  3. Add what you sell

    Add modules and inverters with HSN 8541 and 8504, mounting structures and cable by the metre, and installation as a service under SAC 9954.

  4. Post your first GST invoice

    Pick the customer, add lines and save. The place of supply picks CGST and SGST or IGST for you.

FAQ

Questions, answered

Can one invoice carry panels, the inverter and installation?

Yes. Goods lines carry HSN codes and the installation line carries SAC 9954, each at its own rate. Only the goods lines reduce stock, and the print adds an HSN-wise summary that matches what your accountant needs for GSTR-1.

A homeowner paid ₹50,000 before we ordered panels. Where does that go?

Record it as a payment from the customer without picking an invoice. It stays on account against their name. When the system invoice posts, apply the ₹50,000 to it, and the invoice shows only the balance still due.

Do I bill the subsidy amount to the customer?

Under the PM Surya Ghar rooftop scheme the central subsidy is released to the homeowner's bank account, so installers usually bill the full system price to the homeowner. SimpleERP does not connect to the subsidy portal; file the application there and bill as usual.

Can I bill a 20 kW commercial job in stages?

Yes. Raise one invoice for the material when it reaches the site and a second for installation and commissioning, or convert the quotation once and bill it whole. Each invoice posts on its own, and the customer's ledger adds them up.

Related

See how GST billing works in SimpleERP for solar installers

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