GST Invoice Format India (2026): Mandatory Fields & Free Template
A GST invoice that misses even one mandatory field can cost your buyer their input tax credit — and you a penalty. Here is the exact format prescribed under Rule 46 of the CGST Rules, plus a free generator that gets it right every time.
Skip the formatting. Use our free GST invoice generator — fill in the details, download a compliant PDF, no sign-up needed.
Who must issue a GST invoice
Every registered person making a taxable supply of goods or services must issue a tax invoice under Section 31 of the CGST Act. If you are not registered under GST, you cannot issue a "tax invoice" — you issue a plain bill of supply or a commercial invoice without charging GST.
Mandatory fields under Rule 46
Rule 46 of the CGST Rules, 2017 lists what every tax invoice must contain:
- Name, address, and GSTIN of the supplier.
- A consecutive serial number — unique for the financial year, maximum 16 characters (letters, numbers, '/' and '-' allowed).
- Date of issue.
- Name, address, and GSTIN or UIN of the recipient, if registered.
- If the recipient is unregistered and the invoice value is ₹50,000 or more: name and address of the recipient and the delivery address, along with the state name and code.
- HSN code for goods or SAC for services (4 digits up to ₹5 crore turnover, 6 digits above).
- Description of goods or services.
- Quantity (goods) or unit / unique quantity code.
- Total value of supply, taxable value, and the rate and amount of tax — CGST, SGST/UTGST, IGST, or cess shown separately.
- Place of supply with the state name, for inter-state supplies.
- Whether tax is payable on a reverse charge basis.
- Signature or digital signature of the supplier or an authorised representative.
CGST + SGST vs IGST — which to charge
| Supply type | Tax to charge |
|---|---|
| Seller and buyer in the same state (intra-state) | CGST + SGST (e.g. 9% + 9% for an 18% rate) |
| Seller and buyer in different states (inter-state) | IGST (full 18% as one line) |
| Exports | Zero-rated — with IGST or under LUT without IGST |
The deciding factor is the place of supply, not where your office is. Get this wrong and the tax paid goes to the wrong government — your buyer's credit gets stuck.
Invoice number rules most people miss
- The series must be consecutive and unique per financial year — reset it every April.
- Maximum 16 characters. "INV/2026-27/0042" is valid; gaps or duplicates are not.
- You can run multiple series (e.g. one per branch or per GSTIN) as long as each is internally consecutive.
E-invoicing — does it apply to you?
If your aggregate turnover exceeds ₹5 crore in any financial year since 2017-18, B2B invoices must be reported to the Invoice Registration Portal (IRP) and carry the IRN and QR code it returns. Below that threshold, e-invoicing is optional — a normal Rule 46 invoice is enough.
Common mistakes that invalidate an invoice
- Charging IGST on an intra-state sale (or vice versa).
- Missing or wrong HSN/SAC — the top reason input credit claims get rejected.
- Showing one combined "GST 18%" line instead of splitting CGST + SGST.
- Reusing invoice numbers across financial years.
- No place of supply on inter-state invoices.
Frequently asked questions
What is a GST invoice?
A GST invoice (tax invoice) is the document a registered seller issues when supplying goods or services. It is prescribed under Section 31 of the CGST Act and Rule 46 of the CGST Rules, and it is the basis on which your buyer claims input tax credit.
How many digits should an HSN code have on an invoice?
Businesses with aggregate turnover up to ₹5 crore must use a 4-digit HSN code on B2B invoices; above ₹5 crore, a 6-digit HSN is mandatory. For B2C invoices, 4 digits is the minimum once you cross ₹5 crore turnover.
Is a digital signature valid on a GST invoice?
Yes. Under the Information Technology Act, invoices issued electronically (including through e-invoicing) with a digital signature or QR code are valid. If you issue invoices electronically as per Rule 46, a physical signature is not required.
What is the invoice number rule under GST?
Invoice serial numbers must be unique for a financial year, consecutive, and a maximum of 16 characters. They can contain letters, numbers, and the special characters '/' and '-'. You must reset the series every financial year.
When must a service provider issue the invoice?
For services, the tax invoice must be issued within 30 days of supplying the service (45 days for banks, insurers, and NBFCs). For goods, it is issued at or before the time of removal or delivery.