Invoicing

GST invoice format: what a valid tax invoice must have

Updated 4 November 2026 5 min read

A GST tax invoice is more than a bill; it is the document your buyer uses to claim input tax credit. If a required field is missing, the invoice can be rejected. Here is exactly what a valid GST invoice should contain.

Fields a GST tax invoice must have

Your business name, address and GSTIN.
A consecutive invoice number (unique for the financial year) and the invoice date.
The buyer’s name, address and GSTIN, if they are registered.
Place of supply, and the state with its code, for inter-state sales.
HSN code for goods, or SAC for services, against each line.
Description, quantity, unit and rate of each item.
Taxable value, plus any discount.
GST rate and amount split into CGST and SGST/UTGST, or IGST for inter-state.
Whether tax is payable on reverse charge, where it applies.
Signature or digital signature of the supplier.

CGST + SGST or IGST?

Which tax you charge depends on the place of supply. When the buyer is in the same state as you, the GST is split into CGST and SGST (or UTGST). When the buyer is in another state, you charge a single IGST at the combined rate. Good billing software works this out from the buyer’s state so you do not have to.

A simple example

Suppose you sell 10 units at ₹100 each, GST 18%, to a buyer in your own state. Taxable value is ₹1,000. CGST 9% is ₹90 and SGST 9% is ₹90, so the invoice total is ₹1,180. For a buyer in another state, you would charge IGST 18% of ₹180 instead, for the same ₹1,180.

Bill of supply vs tax invoice

If you are under the composition scheme, or you sell exempt goods, you issue a bill of supply instead of a tax invoice, and you do not charge GST on it. A regular GST taxpayer issues a tax invoice for taxable sales.

Keep your numbering clean

Use a continuous series with no gaps for the financial year.
Do not reuse or edit a number once a bill is issued; use a credit note to correct it.
A short prefix per outlet or series is fine, as long as each number is unique.

FinBill fills GSTIN, place of supply, HSN and the correct CGST/SGST or IGST split for you, keeps your numbering continuous, and prints the invoice in 10+ Tally and Marg style designs or shares a PDF on WhatsApp.

GST rules and due dates change from time to time. Use this as a plain-language starting point and confirm the current rules with your CA or on the official GST portal before you file.

Frequently asked questions

Do I need the buyer’s GSTIN on every invoice?+

You need it when the buyer is registered (a B2B sale). For B2C sales to unregistered customers, the GSTIN is not required.

Is an HSN code compulsory?+

HSN (for goods) or SAC (for services) is required, with the number of digits depending on your turnover. Keeping the code on each item avoids mistakes.

Can I edit an invoice after issuing it?+

Do not change an issued invoice. Make a credit or debit note to adjust it, so your records and GST returns stay consistent.