What fields are mandatory on a GST invoice?

A GST tax invoice must show your name, address and GSTIN, a consecutive invoice number, the date, the customer's name, address and GSTIN where registered, the HSN code for goods or SAC for services, a description of the items, quantity and value, the taxable value, the GST rate and amount split into CGST and SGST or IGST, the place of supply, and a signature. For sales to unregistered buyers above a set value the delivery address is also needed.

What is the difference between a tax invoice and a bill of supply?

A tax invoice is issued by a GST registered seller on taxable supplies and shows GST separately, which lets the buyer claim input tax credit. A bill of supply is issued when no GST is charged, for example by a composition scheme dealer or on exempt goods, and it does not show any tax. In short, if you are collecting GST you raise a tax invoice, and if you are not you raise a bill of supply.

Is HSN code compulsory on an invoice?

Yes, for most businesses. The number of HSN digits you must show depends on your turnover, with smaller firms needing fewer digits and larger firms more. Services use the SAC code instead. Putting the correct HSN or SAC on every line is required for a compliant invoice and helps ensure the right tax rate is applied.

Can I make a GST invoice in Excel?

You can, and many small businesses start there, but Excel puts the burden on you to number invoices correctly, apply the right GST rate, avoid formula errors and keep records for filing. As your volume grows this becomes error prone. Billing software applies the rules automatically, prevents duplicate numbers and pulls your data straight into your returns, which saves time and reduces mistakes.

How many copies of a GST invoice are needed?

For goods, the rules ask for three copies: the original for the buyer, a duplicate for the transporter and a triplicate for the supplier. For services, two copies are enough: the original for the buyer and a copy for the supplier. Software handles this automatically and stores digital copies you can reprint any time.

Invoice Format in India: GST-Compliant Samples (2026)

Getting your invoice format right is not just about looking professional. In India, a GST invoice is a legal document, and missing the fields the law requires can cost your customer their input tax credit and expose you to penalties. The good news is that the rules are clear and, once you set up a correct template, easy to follow every time. This guide lists every mandatory field on a GST invoice, gives you a sample layout you can copy, explains when to raise a bill of supply instead, and weighs an Excel template against proper billing software.

Mandatory fields on a GST invoice

Under GST law, a tax invoice must carry a specific set of details. Leave one out and the document may not be valid for input tax credit. Here is what every GST invoice needs.

Supplier details: your business name, address and GSTIN.
Invoice number and date: a unique, consecutive serial number for the financial year, and the date of issue.
Customer details: the buyer's name and address, plus their GSTIN if they are registered.
HSN or SAC code: the HSN code for each good or the SAC code for each service.
Description, quantity and value: what you sold, how much, and the taxable value after any discount.
Tax breakup: the GST rate and amount, split into CGST and SGST for supply within the same state, or IGST for interstate supply.
Place of supply: the state where the goods or services are delivered, which decides whether CGST plus SGST or IGST applies.
Reverse charge note: a mention of whether tax is payable on reverse charge.
Signature: the signature or digital signature of the supplier or an authorised person.

If the whole idea of GSTINs and tax slabs is new, start with our plain explainer on what GST means and the steps to get a GST number.

A sample GST invoice layout

Here is a complete tax invoice you can use as a model. It shows the intrastate case with CGST and SGST. For interstate sales you would replace those two lines with a single IGST line.

TAX INVOICE

Ravi Traders Invoice No: INV-2026-0421
45 Market Yard, Nashik 422001 Date: 14 August 2026
GSTIN: 27AABCR5678K1Z2 Place of supply: Maharashtra (27)
Phone: 90000 12345

Bill To:
Sunrise Retail Pvt Ltd
Aurangabad 431001
GSTIN: 27AAECS4321M1Z8

-----------------------------------------------------------------
No. Description HSN Qty Rate Taxable GST% Amount
-----------------------------------------------------------------
1 Steel almirah 9403 10 4,500 45,000 18 45,000
2 Office chair 9401 20 1,800 36,000 18 36,000
-----------------------------------------------------------------
 Taxable value 81,000
 CGST @ 9% 7,290
 SGST @ 9% 7,290
-----------------------------------------------------------------
 Invoice total 95,580
-----------------------------------------------------------------
Amount in words: Ninety five thousand five hundred eighty rupees.

Reverse charge: No
Terms: Payment due within 30 days.

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Tax invoice versus bill of supply

Not every sale uses a tax invoice. When you are not charging GST, you raise a bill of supply instead. The two main cases are a dealer registered under the composition scheme, who cannot collect GST from customers, and the sale of goods or services that are exempt from GST. A bill of supply looks similar but it shows no tax breakup, and importantly it does not let the buyer claim input tax credit because no tax was charged. Raising the wrong document is a common error. If you collect GST, it must be a tax invoice. If you do not, it must be a bill of supply. Some businesses supply both taxable and exempt goods and so issue both types depending on the item.

Excel template versus billing software

Plenty of small businesses begin with an Excel invoice template, and for a handful of bills a month that is fine. The trouble appears as you grow. In Excel you have to remember to keep invoice numbers consecutive with no gaps or duplicates, apply the correct GST rate for each HSN code, and avoid the formula slips that creep in when someone copies last month's file. Every mistake is a compliance risk, and at filing time you re key the same figures into your returns, which doubles the work and the chance of error.

Billing software removes most of that risk. It numbers invoices automatically, stores your product list with the right HSN and GST rate against each item, calculates CGST, SGST or IGST based on the place of supply, and keeps every copy for filing. A tool built for India can generate the invoice in the exact format above, share it over WhatsApp or email as a PDF, and track which bills are still unpaid. Our comparison of billing software for small business goes into the practical trade offs, and you can also convert an approved quotation straight into an invoice without retyping.

When to issue the invoice

Timing matters as much as format. GST law sets time limits for raising an invoice. For the supply of goods, the invoice should be issued on or before the goods are delivered or the delivery is arranged. For services, it should generally be issued within 30 days of the service being provided. Issuing late or skipping the invoice creates gaps in your records and can hold up your customer's input tax credit, which strains the relationship. Larger businesses whose turnover crosses the prescribed limit must also generate an e invoice with an invoice reference number from the government portal, so check whether your turnover has reached that stage. Whatever your size, raising the invoice promptly and in the right order keeps both your books and your customer's clean.

Keep your invoices consistent

Whatever tool you choose, consistency is what keeps you compliant and trusted. Use one continuous number series for the financial year, show the tax clearly on every bill, put the correct HSN or SAC on each line, and store copies you can produce if asked. Set the template up correctly once and the format takes care of itself. IndiaCRM issues fully GST compliant invoices, remembers each customer's details and GSTIN, and pulls everything you need for filing into one place, free.