GST Invoice: The Complete Guide for Businesses (2026)

A GST invoice (also called a tax invoice) is a document a registered supplier issues to a buyer for the sale of goods or services, showing the value of the supply, the tax charged, and the details needed for both parties to stay compliant under GST.

It serves three purposes at once: it's proof of sale, it's the basis on which you collect and pay GST to the government, and it's the document your buyer needs to claim ITC on their purchase.

Not every sale needs the same document. Here's a quick breakdown:

• 1Tax Invoice — used for all taxable supplies by a regular registered dealer.
• 2Bill of Supply — issued instead of a tax invoice when you're selling exempt goods/services, or if you're registered under the composition scheme (since composition dealers can't charge GST separately).
• 3Revised Invoice — issued to correct or update an invoice already raised between the date your GST registration was granted and the date your certificate was issued.
• 4Credit Note / Debit Note — issued when the invoice value needs to be reduced (credit note) or increased (debit note) after the original invoice — for example, due to a return, discount, or pricing correction.
• 5e-Invoice — a tax invoice that has been electronically reported to the government's Invoice Registration Portal (IRP) and carries a unique Invoice Reference Number (IRN) and QR code.
• 6Self-Invoice — raised by a registered recipient (not the seller) when buying under reverse charge from an unregistered supplier, since the unregistered person can't issue a GST invoice.
• 7Payment Voucher — issued alongside a self-invoice, at the time payment is made to the unregistered supplier, to document discharge of the RCM tax liability.
• 8Consignment Note — issued by a Goods Transport Agency (GTA) for transporting goods by road.

A consignment note is the document that turns an ordinary truck or tempo operator into a Goods Transport Agency (GTA) under GST — and it's this classification that decides whether GST applies at all.

A consignment note is serially numbered and typically contains:

• 1Name of the consignor and consignee
• 2Registration number of the vehicle carrying the goods
• 3Details of the goods being transported
• 4Place of origin and destination
• 5The person liable to pay tax (i.e., whether GST is payable by the GTA or the recipient under reverse charge)

Issuing a consignment note signals that the transporter has taken on responsibility (lien) for the goods until delivery — this is what makes them a GTA. An individual truck owner who transports goods without issuing a consignment note isn't treated as a GTA, and that service is generally exempt from GST. Once a consignment note is issued, GTA services become taxable (commonly at 5% without ITC or 12% with ITC, depending on the option chosen), and in many cases the tax is payable by the recipient under reverse charge rather than the GTA itself.

If you run a transport business or regularly hire transporters, checking whether a consignment note is being issued is the first step to knowing your GST liability on freight.

Rule 46 of the CGST Rules lays out exactly what must appear on a tax invoice. Missing any of these can make the invoice non-compliant:

• 1Supplier's name, address, and GSTIN
• 2A consecutive, unique invoice number (up to 16 characters, using only letters, numerals, hyphens, and slashes)
• 3Date of issue
• 4Recipient's name, address, and GSTIN/UIN (if registered)
• 5If the recipient is unregistered and the invoice value is ₹50,000 or more: their name, address, delivery address, and the state name and code
• 6HSN code (for goods) or SAC code (for services)
• 7Description of the goods or services
• 8Quantity and unit of measurement (for goods)
• 9Total value of the supply
• 10Taxable value (after any discount or abatement)
• 11Rate of tax for each component — CGST, SGST/UTGST, IGST, and cess, shown separately
• 12Amount of tax for each component, shown separately
• 13Place of supply and state name, where the supply is inter-state
• 14Delivery address, if different from the place of supply
• 15Whether tax is payable under reverse charge
• 16Signature or digital signature of the supplier or their authorised representative

A small business generating invoices manually should keep this list handy — most invoicing or accounting software will build these fields in automatically.

Timing matters under GST — issuing an invoice late is itself a compliance lapse.

• 1For goods: before or at the time of removal (if the goods are being transported), or before or at the time of delivery in other cases.
• 2For services: within 30 days of the date of supply. Banks and financial institutions get a longer window — 45 days.

e-Invoicing means reporting your B2B invoice details to the government's Invoice Registration Portal (IRP), which validates the invoice and returns it with an IRN and a QR code. As of 2026, this is mandatory for businesses with an aggregate annual turnover above ₹5 crore in any financial year since 2017-18, for their B2B and export invoices.

• 1If e-invoicing applies to you and your invoice doesn't carry a valid IRN and QR code, it's treated as invalid under GST law — which means your buyer cannot claim ITC on it.
• 2Businesses with turnover above ₹10 crore have an additional rule: invoices must be reported to the IRP within 30 days of issue, or the portal will reject them.
• 3Two-factor authentication is now required to log in to the e-invoice portal, so make sure whoever handles your billing has this set up.

If your turnover is below ₹5 crore, you can still issue a regular tax invoice — e-invoicing simply doesn't apply to you yet.

• 1Skipping the invoice serial number rules — reusing numbers or breaking sequence within a financial year.
• 2Wrong HSN/SAC codes — leads to reconciliation issues in GSTR-1 and GSTR-2B.
• 3Charging IGST instead of CGST+SGST (or vice versa) — always check the place of supply first.
• 4Not issuing an e-invoice when required — makes the invoice invalid and blocks your customer's ITC.
• 5Missing the reverse charge declaration — this single Yes/No field is easy to overlook but mandatory.
• 6Delayed invoicing for services — issuing outside the 30-day window (45 days for banks/NBFCs) is a compliance gap even if the tax is eventually paid.
• 7Not self-invoicing for RCM purchases from unregistered persons — skipping this means you can't correctly discharge the RCM liability or claim ITC on it.
• 8Hiring transporters without checking for a consignment note — this affects whether the freight is even taxable and who's liable to pay the GST.

An incorrect or incomplete GST invoice isn't just a paperwork issue. It can lead to your buyer being denied ITC, mismatches in your GST returns, notices from the department, and in serious or repeated cases, penalties. Since your invoice data flows directly into your GSTR-1 and, through auto-population, into your buyer's GSTR-2B, an error at the invoice stage tends to multiply downstream.

PJRJ & Associates helps businesses across Delhi NCR and India with GST-compliant invoicing setups, e-invoicing readiness, RCM self-invoice processes, and GSTR-1 quality checks — so ITC claims and return filings stay clean.

• 1GST invoice and bill-of-supply process review
• 2HSN/SAC mapping by turnover slab
• 3e-Invoice / IRP onboarding and IRN checks
• 4Self-invoice and payment voucher workflows for RCM
• 5GSTR-1 and GSTR-2B mismatch prevention