GST Invoice Format: What Must Be on a Tax Invoice in India

A tax invoice is not just a receipt. For a registered buyer, it is the document that lets them claim input tax credit on the GST they paid you. If key details are missing or wrong, their credit can be questioned, and they will come back to you to fix it.

For you, invoices are the raw material for your returns. Every error on a bill becomes an error in GSTR-1, and an error in GSTR-1 shows up as a mismatch on your buyer's side.

The rules on invoice contents are set out in the GST law and are revised from time to time. Treat this guide as a practical checklist, and confirm anything unusual with your CA.

A tax invoice from a registered supplier should carry the following. Most billing software prints these on its own once your business details are set up correctly, but it is worth holding one printed bill against this list.

• Your name, address and GSTIN.
• An invoice number that runs in a consecutive series for the financial year, using letters, numbers, hyphens or slashes, no longer than 16 characters.
• The date of issue.
• The buyer's name, address and GSTIN, if they are registered.
• For an unregistered buyer, their name and address, and the delivery address with the state, when the invoice value is above the limit set in the rules.
• The HSN code for goods, or SAC for services, with as many digits as your turnover band requires.
• A description of the goods or services.
• Quantity and unit, such as 10 PCS or 2.5 KGS.
• The total value, and the taxable value after any discount.
• The tax rate and tax amount, shown as CGST and SGST for a sale within your state, or IGST for a sale to another state.
• The place of supply, with the state name, for a sale to another state.
• Whether tax is payable on reverse charge.
• Your signature or digital signature, or that of someone you have authorised.

Say you run a stationery wholesale business in Pune and sell to a registered shop in the same city. The bill has two lines: 50 notebooks at ₹40 each, and 20 boxes of pens at ₹120 a box, with a 5% trade discount on the pens. For this example, assume both are taxed at 18%. Check the actual rate for your own HSN codes, because rates change.

Notebooks: 50 × ₹40 = ₹2,000. Pens: 20 × ₹120 = ₹2,400, less a 5% discount of ₹120, giving ₹2,280. The discount comes off before tax. Taxable value is ₹2,000 + ₹2,280 = ₹4,280.

The buyer is in the same state, so the tax is split in half. CGST at 9% is ₹385.20 and SGST at 9% is ₹385.20. The invoice total is ₹4,280 + ₹770.40 = ₹5,050.40. If you round it to ₹5,050, show the round-off as its own line.

If the same shop were in Bengaluru, the place of supply would be Karnataka and you would charge IGST at 18%, which is ₹770.40, as one line instead of two. The total is identical. The split is not. Charging CGST and SGST on an inter-state sale is one of the most common errors, and it means the tax has been paid under the wrong head.

Invoice numbers must run in an unbroken series within a financial year. You can have more than one series, for example one per store, or one for wholesale and one for retail. Each must still be consecutive, and the same number must never be used twice in a year.

Problems usually start when two people bill at once on separate devices, or when a cancelled bill's number is reused. Never reuse a number. Cancel the bill and keep it on record.

A prefix that shows the store and the year keeps series apart, such as PUN/26-27/0001. Keep the prefix short. Something like PUNE-WHOLESALE-2026-27/00001 is easy to read but runs past 16 characters.

Not every sale gets a tax invoice. If you are under the composition scheme, or you sell only exempt goods, you issue a bill of supply instead, and you cannot charge GST on it.

When goods come back, or you give a discount after the sale, issue a credit note that refers to the original invoice. Do not edit the original. If you undercharged and need to collect more, issue a debit note. Both go into your returns.

For goods, the rules expect more than one copy of the invoice: an original for the buyer, a duplicate for the transporter and a triplicate for you. Larger consignments may also need an e-way bill, and businesses above a turnover threshold must report B2B invoices to the government portal as e-invoices. The thresholds have changed over the years, so ask your CA whether either applies to you today.

Each of these is small on its own. Over a month they add up to returns that do not match your buyers' records, and phone calls you would rather not take.

• A wrong or outdated GSTIN for the buyer. Check it before the first sale and whenever a customer moves or changes their business name.
• CGST and SGST charged on an inter-state sale, or IGST on a local one.
• A missing, vague or wrong HSN code.
• A discount taken off after tax instead of before, so the taxable value is wrong.
• Skipped or duplicate invoice numbers.
• Totals that do not add up because each line was rounded by hand.

Kownt X stores HSN and tax codes on each product, prints A4 GST invoices and thermal receipts, and gives each store its own invoice number series. From the same sales it prepares GSTR-1 data, input tax from purchases, e-invoice and e-way bill files ready to upload, and a Tally export for your CA. It does not file returns for you. You or your CA file them on the portal.