GST Invoice Format for Small Businesses — Every Field You Must Include

A wrong or incomplete invoice can cost your customer their input tax credit, and that can cost you the customer. The good news: a correct GST invoice is not complicated. It just has to show the right details, every time.

Here is everything a GST tax invoice must include, in plain language.

Who must issue a tax invoice?

Every GST-registered business that sells taxable goods or services must issue a tax invoice.

• Composition dealers issue a bill of supply instead, with the words "composition taxable person, not eligible to collect tax on supplies".
• Businesses selling only exempt goods or services also issue a bill of supply.

The 16 details every GST tax invoice must show

About you (the supplier)

1. Your business name and address
2. Your GSTIN

About the invoice

1. Invoice number: one continuous series per financial year, up to 16 characters, using letters, numbers, hyphen "-" or slash "/" only. Example: INV/26-27/001
2. Date of issue

About your customer

1. Customer name and address
2. Customer GSTIN, if they are registered
3. For unregistered customers with an invoice of ₹50,000 or more: their name, address, delivery address, and state name and code

About what you sold

1. Description of the goods or services
2. HSN code for goods or SAC for services
3. Quantity and unit for goods (Nos, Kg, Month…)
4. Total value
5. Taxable value after any discount

About the tax

1. GST rate and amount, shown separately:

• CGST + SGST (or UTGST) when you and the customer are in the same state
• IGST when the customer is in another state

1. Place of supply with the state name, for sales to another state
2. Whether tax is payable under reverse charge (write "Yes" or "No")

Signature

1. Signature or digital signature of you or your authorised person

How many HSN digits do you need?

It depends on your turnover in the previous year:

• Up to ₹5 crore: a 4-digit HSN code on invoices to registered businesses (B2B)
• Above ₹5 crore: a 6-digit HSN code on all invoices

When in doubt, use 6 digits. It is always accepted.

CGST + SGST or IGST? A quick example

You are in Delhi and sell a ₹10,000 service at 18% GST.

• Customer in Delhi (same state): CGST 9% = ₹900 + SGST 9% = ₹900. Total ₹11,800
• Customer in Mumbai (other state): IGST 18% = ₹1,800. Total ₹11,800

The total is the same. Only how the tax is split changes, and getting it wrong means the customer cannot claim the credit.

When must you issue the invoice?

• Goods: before or at the time of removal or delivery
• Services: within 30 days of providing the service

How many copies?

• Goods: three copies. Original for the buyer, Duplicate for the transporter, Triplicate for you.
• Services: two copies. Original for the customer, Duplicate for you.

A PDF sent by email counts. Keep your own copy safe for at least 6 years.

What about e-invoicing?

Businesses whose turnover crossed ₹5 crore in any year since 2017-18 must generate an e-invoice (IRN and QR code) on the government portal for B2B sales. Below that, a normal tax invoice is enough.

Quotation, proforma and tax invoice: what's the difference?

• Quotation: your price offer. Not a tax document.
• Proforma invoice: a request for advance payment. Not a tax document, and no GST is due on it.
• Tax invoice: the real GST document. It goes into your GSTR-1 and the customer's input tax credit.

Never use a proforma's number as your tax invoice number. Tax invoices need their own continuous series.

Common mistakes to avoid

• Gaps or repeats in invoice numbers
• Wrong state, so CGST + SGST is charged instead of IGST, or the other way round
• Missing HSN/SAC codes
• Editing an issued invoice. Cancel it or issue a credit note instead.
• Starting a new year with the old series. Begin a fresh series every 1 April.

The quick checklist

Before you send any invoice, check:

• [ ] Your GSTIN and the customer's GSTIN
• [ ] Correct invoice number and date
• [ ] HSN/SAC code on every line
• [ ] CGST + SGST for the same state, IGST for another state
• [ ] Place of supply
• [ ] Reverse charge: Yes or No
• [ ] Signature

Make GST invoices in one click

DialDesk CRM creates GST-ready documents from your leads: quotation → proforma → tax invoice, all in one place.

• Picks CGST + SGST or IGST from the customer's state
• Numbers invoices per financial year automatically (INV/26-27/001)
• Locks issued invoices so they cannot be edited by mistake
• Adds your logo and a UPI QR code so customers pay faster
• Prepares your monthly GSTR-1 and GSTR-3B figures, with Excel and JSON export for your accountant

Start the free trial and send your next GST invoice in under a minute.

This guide is general information, not tax advice. GST rules change from time to time, so please confirm the details for your business with your CA.