GST Invoice Format — Free Tax Invoice Generator

What must be on a GST tax invoice

A tax invoice is the document a GST-registered business issues when it makes a taxable supply. It is also what your customer relies on to claim input tax credit, so a missing or wrong detail costs them money, not just you. Section 31 of the CGST Act, 2017 requires the invoice, and the invoice rules under GST law list the details it must carry. The list below covers what those rules generally ask for; check the current rules before you rely on it, because they are amended from time to time.

Your name, address and GSTIN

Exactly as on your GST registration certificate.

A unique invoice number

In one or more series, consecutive and unique for the financial year. The rules cap its length, so keep it short, e.g. INV/2026-27/001.

The date of issue

The date you raise the invoice, not the date the customer pays.

The customer's name, address and GSTIN

The GSTIN if they are registered. For an unregistered customer, the rules ask for extra details on larger invoices — check what applies.

Place of supply

The state name, and the state code where it is needed. It decides whether you charge CGST + SGST or IGST.

HSN or SAC code

HSN for goods, SAC for services. How many digits you must show depends on your turnover; check the current requirement.

Description, quantity and value

What you supplied, how much, the rate per unit, any discount, and the taxable value after it.

Rate and amount of tax

The GST rate on each line, and the CGST, SGST/UTGST or IGST charged.

Whether tax is payable on reverse charge

A short statement saying yes or no. If yours is a reverse-charge supply, add it to the notes.

Signature

Of you or an authorised person, by hand or with a digital signature.

Tax invoice, bill of supply or proforma invoice?

Founders often use these names loosely, but they are different documents with different effects. The one you issue depends on whether you are registered, what you are supplying, and whether the sale has actually happened yet.

A proforma invoice is the one most often misused. It is a quotation in invoice form, useful when a customer needs a document to approve a purchase or release an advance. It is not a tax invoice, it does not go in your GST return, and the customer cannot claim credit on it. Once the supply is made, issue a proper tax invoice with its own number from your invoice series.

CGST + SGST or IGST: it depends on the place of supply

GST on a supply is either split between the Centre and the state, or charged as one integrated tax. Which one applies is decided by comparing two things: the state you supply from (the state in your GSTIN), and the place of supply.

If they are the same state, it is an intra-state supply. You charge CGST and SGST (or UTGST in a Union Territory), each at half of the GST rate on the line. On this invoice, a line with a rate you type is split into two equal halves automatically. If they are different states, it is an inter-state supply and you charge IGST at the full rate.

The place of supply is not always where the customer's office is. For goods it is generally where the movement of goods ends. For most services to a registered business it is generally the customer's location, but there are special rules for things like events, property, transport and training. Supplies to a unit in a Special Economic Zone are treated as inter-state even when the SEZ is in your own state. When in doubt, ask your CA; the generator flags it when the state you typed and the supply type don't match, but it cannot decide the place of supply for you.

Getting the split wrong is not a rounding problem. Tax paid under the wrong head is not simply moved across: you generally have to pay it under the right head and claim a refund of the wrong one, which takes time and paperwork.

Common mistakes on GST invoices

Most invoice problems surface weeks later, when your customer cannot see the credit in their account or a notice asks why the figures don't match. These are the ones that come up most often for small businesses.

Wrong place of supply

Charging CGST + SGST on an inter-state sale, or the reverse. Fix it with a credit note and a fresh invoice, not by editing the old one.

Wrong or mistyped GSTIN

Your customer loses the credit until it is corrected. Check the GSTIN on the GST portal's search before the first invoice to a new customer.

Duplicate or broken numbering

Two invoices with the same number, or a series that restarts mid-year, both raise questions. Use one series per financial year and never reuse a cancelled number.

Tax worked out on the total, not each line

With items at different rates, the tax has to be worked out line by line. This generator does that and rounds each line to the paisa.

Missing HSN or SAC

Leaving it blank, or using a code that does not match what was sold.

Issuing a proforma instead of a tax invoice

If the sale has happened, the customer needs a tax invoice to claim credit.

Do you need e-invoicing?

E-invoicing does not mean emailing a PDF. It means reporting each business-to-business invoice to the government's Invoice Registration Portal, which returns an Invoice Reference Number (IRN) and a signed QR code that must appear on the invoice.

It applies to businesses whose aggregate turnover is above a limit set by the government. That limit has been lowered several times since e-invoicing started, so check the current limit on the GST portal or with your CA rather than relying on an older article. If you are below it, an invoice like the one this generator makes is enough. If you are above it, you can still use this to draft the content, but the invoice you send must be generated through the e-invoicing system, usually from your accounting software.

Separately, moving goods above a certain value usually needs an e-way bill. That has its own limit and rules; check them if you ship goods.

Corrections, copies and records

Once an invoice has been issued and reported, don't edit it and send it again under the same number. If the value or tax was too high, issue a credit note; if it was too low, a debit note. Both reference the original invoice and go in your return for the period.

The rules ask for copies of a goods invoice in triplicate (original for the buyer, duplicate for the transporter, triplicate for you) and a services invoice in duplicate. With a PDF, that simply means keeping your copy and marking which is which if you print them.

Keep invoices, credit and debit notes with your books for as long as GST law requires; check the current period with your CA. A simple habit helps: save every invoice as a PDF named by its number, in a folder per financial year.