GST Invoice Format India 2026: What Every Field Must Say

If your customer cannot claim input tax credit because your invoice is missing a field, they will not order from you again. Getting the GST invoice format right is not a nice-to-have. It is the difference between keeping and losing a client.

The good news is that a compliant invoice is mostly a checklist. Once you know the fields and the two or three rules that trip people up, you can produce a correct invoice every time. You can also skip the manual work entirely with the free GST invoice generator, which puts every required field in the right place.

Who needs to issue a GST invoice?

Any GST-registered business must issue a tax invoice for taxable supplies. Registration becomes mandatory once your turnover crosses ₹40 lakh for goods or ₹20 lakh for services, and many businesses register below that voluntarily so they can claim input tax credit. If you are registered, every taxable sale needs a proper invoice, full stop.

The mandatory fields

A GST invoice must carry a specific set of details, the fields mandated under Rule 46 of the CGST Rules by the CBIC. Get all of them on the document and you are compliant:

The supplier's name, address and GSTIN. A unique, sequential invoice number. The date of issue. The customer's name and address, plus their GSTIN for a B2B sale. The place of supply, which decides the tax type. The HSN code for goods or SAC code for services. A description of the goods or services, with quantity and unit. The taxable value and any discount. The applicable tax rate and the tax amount split into CGST and SGST, or IGST. And a signature or digital signature of the supplier. Miss one and the invoice may be questioned.

CGST vs SGST vs IGST

This is where most errors happen, and it is genuinely simple once you see it. Look at where your customer is. If the supply is within your own state, you split the tax into CGST and SGST, half and half. If the supply goes to another state, you charge a single IGST at the full rate instead.

For example, on a ₹10,000 sale at 18% within the same state, you charge ₹900 CGST and ₹900 SGST. On the same sale to another state, you charge ₹1,800 IGST. The total tax is identical, only the split changes. The GST calculator works out the split for you instantly.

B2B vs B2C invoices

A B2B invoice goes to another registered business and must include their GSTIN, because they will use the invoice to claim input tax credit. A B2C invoice goes to a final consumer who cannot claim credit, so it does not need the buyer's GSTIN. Either way the invoice still needs every mandatory Rule 46 field, whatever its value. What changes with value is how you report B2C sales in your GSTR-1: inter-state B2C invoices up to ₹1,00,000 go in as a consolidated, state-wise summary (B2CS), while inter-state invoices above ₹1,00,000 must be reported one by one with the place of supply (B2CL). That ₹1 lakh limit was reduced from ₹2.5 lakh on 1 August 2024, when the CBIC lowered the inter-state B2C reporting threshold (Notification No. 12/2024 - Central Tax), so check the value before you file.

HSN and SAC codes

HSN codes classify goods and SAC codes classify services. The required number of digits depends on your turnover, with larger businesses needing more digits. Common service codes include 998314 for IT consulting. Putting the correct code on the invoice applies the right tax rate and keeps you compliant, so look yours up once and reuse it.

E-invoice rules in 2026

For larger businesses, e-invoicing is mandatory. If your turnover is above the current ₹5 crore threshold, every B2B invoice must be registered on the government portal to generate an Invoice Reference Number and a QR code. Below that threshold it is not required yet, but the limit has been lowered repeatedly, so confirm where it stands for your turnover before assuming you are exempt.

Create a GST invoice in minutes

You do not need accounting software to produce a compliant invoice. The free invoice generator includes every mandatory field, handles the CGST, SGST and IGST split, and outputs a clean PDF you can email or print. Pair it with the GST calculator to double-check the tax, and the quotation generator when you need to send an estimate first.

How to generate an IRN on the IRP portal, step by step

If your aggregate turnover crosses ₹5 crore in any financial year, e-invoicing is mandatory. That does not mean the government designs your invoice. It means each B2B invoice must be registered on the Invoice Registration Portal, which returns a unique Invoice Reference Number and a signed QR code you print on the document.

The flow looks like this:

• Prepare the invoice in your accounting or billing software with all the mandatory fields covered above.
• Generate the JSON in the government's e-invoice schema. Most accounting tools export this with one click.
• Upload to the IRP at einvoice1.gst.gov.in, directly, through your GST Suvidha Provider, or via API.
• The IRP validates and signs it and sends back the IRN plus a digitally signed QR code.
• Print the IRN and QR code on the final invoice you give the customer. The invoice is not legally valid for ITC without them.

The detail then flows automatically into your GSTR-1, which cuts down on reconciliation later. Calculate the tax lines first with the GST calculator so the figures you upload are correct.

Common GST invoice mistakes that get ITC rejected

Input tax credit is where invoices go wrong, because a small slip on your invoice can cost your customer the credit. These are the eight that come up again and again:

• Wrong or missing GSTIN. Always verify the buyer's GSTIN on the portal before billing.
• Missing HSN or SAC code. The required number of digits depends on turnover, so do not leave it blank.
• Wrong place of supply. This decides CGST plus SGST versus IGST; getting it wrong charges the wrong tax.
• Invoice not uploaded in GSTR-1. If it never reaches the buyer's GSTR-2B, they cannot claim the credit.
• Missing signature or valid IRN. An unsigned invoice, or an e-invoice without an IRN, is incomplete.
• Incorrect tax rate. Using an old rate after a change leads to short or excess tax and a mismatch.
• Claiming blocked credits. Items under Section 17(5), such as personal-use goods, are not eligible.
• Mismatch with GSTR-2B. If your books and the auto-populated statement disagree, fix it before filing.

Most of these are avoidable with a clean template and a quick check before you send. Build the document with the invoice generator and confirm the tax split with the GST calculator.

⚠️Disclaimer: This article is general information, not professional tax or legal advice. GST rules and thresholds change. Confirm the current requirements with the GST portal or a chartered accountant before relying on them.