On this page
in short
- Rule 46 of the CGST Rules lists 16 details that a tax invoice must carry.
- The invoice number must be unique for the financial year and no longer than 16 characters.
- Businesses up to ₹5 crore turnover use 4-digit HSN codes, and those above it use 6 digits.
- A missing or wrong detail can cost your buyer their input tax credit, and cost you the customer.
A GST invoice is more than a bill. It is the document your buyer uses to claim input tax credit (ITC), and the one an officer reads first in any check. If a required detail is missing or wrong, the buyer’s credit is at risk, and the phone call that follows is never pleasant.
Rule 46 of the CGST Rules lists what a tax invoice must contain. There are 16 items, and they fall into eight groups.
The Invoice at a Glance
- 1Supplier name, address and GSTIN
- 2Invoice number and date
- 3Buyer name, address and GSTIN
- 4Place of supply and delivery address
- 5Description, HSN or SAC code, quantity and unit
- 6Total value and taxable value after discount
- 7Tax rate and tax amount, split into CGST, SGST or IGST
- 8Reverse charge note and signature
The 16 Fields
About you, the supplier
- Name, address and GSTIN of the supplier.
- A consecutive invoice number, unique for the financial year. It can be up to 16 characters, using letters, numbers, hyphens and slashes.
- Date of issue.
About the buyer
- Name, address and GSTIN of the buyer, if registered.
- For an unregistered buyer, the name, address and delivery address with state name and code, when the invoice value is ₹50,000 or more.
About the goods or services
- HSN code for goods or SAC code for services.
- Description of the goods or services.
- Quantity and unit, for goods.
- Total value.
- Taxable value, after any discount.
About the tax
- Rate of tax: CGST, SGST, IGST, UTGST or cess.
- Amount of tax charged under each.
- Place of supply, with the state name, for a sale to another state.
- Delivery address, where it differs from the place of supply.
- Whether tax is payable on reverse charge.
- Signature or digital signature of the supplier or an authorised person.
If e-invoicing applies to you, the invoice must also carry the IRN and QR code. See e-invoicing under GST.
How Many Digits of HSN
| Turnover in the previous financial year | HSN digits on the invoice |
|---|---|
| Up to ₹5 crore | 4 digits, mandatory on B2B invoices |
| Above ₹5 crore | 6 digits on all invoices |
Tax Invoice or Bill of Supply
Not every sale needs a tax invoice.
- Tax invoice: for taxable sales by a regular taxpayer.
- Bill of supply: for exempt goods or services, and for all sales by a composition dealer. It shows no tax.
- Consolidated invoice: for sales under ₹200 to unregistered customers who do not ask for a bill, you may issue one combined invoice at the end of the day.
For goods, issue the invoice before or at the time the goods leave. For services, issue it within 30 days of providing the service.
Mistakes That Cause Trouble
Invoices that get questioned
- Buyer's GSTIN typed wrong, so the credit goes nowhere
- Invoice numbers repeated or restarted mid-year
- CGST and SGST charged on a sale to another state
- Old tax rate used after a rate change
- HSN code missing or too short
Invoices that pass
- GSTIN picked from the saved customer record
- One number series that runs through the year
- IGST applied automatically from the place of supply
- Rates stored on the item and updated once
- HSN code saved on every item
Get It Right Once
Every item on the right-hand side of that comparison comes from the same idea: store the detail once, and let the software fill it in. In Saniiro billing, customer GSTINs, HSN codes and tax rates are saved on the customer and item, and the tax split is worked out from the place of supply. Each invoice then updates stock, accounts and your GST reports together.
This article is general information as of 5 October 2026, not tax or legal advice. GST rules, limits and due dates change by notification, so check the GST portal or ask your chartered accountant before you act on it.