GST invoice format: every field your tax invoice must have

A tax invoice is the main document under GST. Your customer needs it to claim input tax credit, and you report it in GSTR-1. If a field is missing, your customer can lose their credit, so the format matters.

Mandatory fields on a GST tax invoice

Rule 46 of the CGST Rules lists what a tax invoice must show:

1. Your name, address and GSTIN.
2. An invoice number (see the rules below).
3. The date of issue.
4. The customer's name, address and GSTIN, if they are registered.
5. If the customer is unregistered and the value is ₹50,000 or more: their name, address, delivery address and the state name and code.
6. HSN code for goods or SAC code for services.
7. Description of the goods or services.
8. Quantity and unit (Nos, Kg, Box and so on).
9. Total value of the supply.
10. Taxable value after any discount.
11. GST rate: CGST and SGST (or UTGST) for a sale within your state, IGST for a sale to another state, and cess if any.
12. Tax amount for each of these.
13. Place of supply and the state name, for sales to another state.
14. Delivery address, if it is different from the place of supply.
15. Whether tax is payable on reverse charge.
16. Your signature or digital signature, or that of an authorised person.

Invoice number rules

• Up to 16 characters. Letters, numbers, hyphen (-) and slash (/) are allowed.
• Numbers must run in order and be unique for the financial year. Most businesses restart every April, for example INV/26-27/001.
• You can keep separate series, for example one for each branch, as long as each is unique.

How many HSN digits?

More detail is in our guide to HSN codes on invoices.

How many copies, and by when?

• Goods: three copies marked Original for recipient, Duplicate for transporter, and Triplicate for supplier. Issue the invoice before or at the time the goods leave.
• Services: two copies, Original for recipient and Duplicate for supplier. Issue it within 30 days of providing the service.
• With an online invoice you share the original as a link or PDF and keep your copy in the software.

CGST + SGST or IGST?

Compare your state with the place of supply. Same state: split the GST into two equal halves, CGST and SGST. For example, 18% becomes 9% + 9%. Different state: charge the full rate as IGST. The first two digits of a GSTIN are the state code, so 27 is Maharashtra and 29 is Karnataka.

Small sales and special cases

• For a sale below ₹200 to an unregistered customer, you can skip a separate invoice if you make one consolidated invoice for such sales each day.
• Composition dealers and sellers of exempt goods issue a bill of supply, not a tax invoice.
• Businesses with turnover above ₹5 crore must also generate an IRN through the e-invoice system.