GST Invoice Format: Mandatory Fields Every Indian Business Must Include

A GST tax invoice isn't just a bill. It is the document your customer uses to claim input tax credit, and the record tax officers look at during an audit. Missing or incorrect fields can cost your customer their credit and create problems for you. Here's what a GST-compliant invoice must include.

Mandatory fields on a GST tax invoice

• Supplier's name, address and GSTIN
• A unique, consecutive invoice number for the financial year (up to 16 characters, using letters, numbers, '-' or '/')
• Date of issue
• Recipient's name, address and GSTIN (for registered recipients)
• Place of supply, with state name and code, for inter-state supplies
• HSN code for goods or SAC for services
• Description, quantity and unit of the goods or services
• Total value and taxable value after discounts
• GST rate and amount, split into CGST and SGST, or IGST
• Whether tax is payable under reverse charge
• Signature or digital signature of the supplier or authorised person

How many HSN digits do you need?

HSN requirements depend on your turnover. Businesses with aggregate turnover up to ₹5 crore generally need at least a 4-digit HSN on B2B invoices, while those above ₹5 crore need at least 6 digits. Check the latest notification for B2C requirements and any changes.

These rules are summarised from the CGST Rules and related notifications as of our last review. Confirm current requirements with your tax advisor or the official GST portal.

Tax invoice vs bill of supply

Registered businesses charging GST issue a tax invoice. Businesses under the composition scheme, or those supplying exempt goods, issue a bill of supply instead, which doesn't show tax and doesn't allow the buyer to claim input credit.

Common invoice mistakes to avoid

• Charging CGST and SGST on an inter-state sale (it should be IGST)
• Missing or wrong customer GSTIN, which blocks their input credit
• Breaks or duplicates in invoice numbering
• Incorrect HSN codes or tax rates
• Not issuing credit notes properly for returns

Let software do the checking

Good billing software stores GST rates and HSN codes per product, decides between CGST/SGST and IGST from the place of supply, and keeps invoice numbers in sequence automatically. Saarthi does all of this, and the same invoice data flows into your GSTR-1 so your returns match your bills.