GST Invoice Requirements in India: Rules & Mistakes

Updated 14 November 2026 · Standard formula, shown below

GST invoices in India must include 16 mandatory fields, and e-invoicing applies to businesses with turnover above ₹5 crore for B2B transactions. This article explains the required details, the e-invoicing rules, and the most common mistakes that lead to penalties or input tax credit (ITC) rejection.

What Is a GST Invoice?

A GST invoice is a document issued by a registered supplier for every supply of goods or services. It serves as proof of the transaction, enables the recipient to claim input tax credit, and is used to compute the supplier’s tax liability. Under the GST law, an invoice must be issued before or at the time of supply, and it must contain all the prescribed particulars. For goods, the invoice is usually issued before the goods are removed; for services, it is issued before or within 30 days of the supply (45 days for banking and insurance).

Mandatory Fields on a GST Invoice

Rule 46 of the CGST Rules, 2017 lists the fields that must appear on a tax invoice. Missing any of these can make the invoice invalid for ITC purposes.

Name, address, and GSTIN of the supplier
Serial number of the invoice (unique, sequential, for the financial year)
Date of issue
Name, address, and GSTIN/UID of the recipient (if registered)
HSN code of the goods or accounting code of services
Description of goods or services
Quantity and unit price for goods (where applicable)
Total value before tax
Rate of GST (CGST, SGST, or IGST) and the amount
Whether tax is payable on reverse charge
Place of supply and the recipient’s state name
Signature or digital signature of the supplier

For exports, you must also mention the shipping bill number and date, and the invoice must be in foreign currency if required. For exempt supplies, a bill of supply is used instead of a tax invoice.

E-Invoicing Rules in India

E-invoicing is a system where B2B invoices are authenticated by the GST Network (GSTN) through the Invoice Registration Portal (IRP). It applies to businesses with aggregate turnover exceeding ₹5 crore in any financial year since 2017-18. The turnover threshold has been reduced over time: it was ₹500 crore from October 2020, then ₹100 crore from January 2021, ₹50 crore from April 2021, ₹20 crore from April 2022, and ₹5 crore from August 2023. E-invoicing does not apply to SEZ units, insurance companies, banks, and passenger transport services.

The process is straightforward: the supplier generates the invoice in their accounting software, uploads it to the IRP, and receives a unique Invoice Reference Number (IRN) and a QR code. The IRN is generated using a hash of the supplier’s GSTIN, the invoice number, and the financial year. The final invoice must include the IRN and QR code. E-invoicing is mandatory for all B2B invoices, including exports, but not for B2C invoices (though the QR code is required for B2C invoices above ₹10,000).

Common Mistakes to Avoid

Many errors lead to notice or rejection of ITC. Here are the most frequent ones:

Wrong GSTIN of the recipient – a single digit error makes the invoice invalid for ITC.
Missing or incorrect HSN code – for supplies above ₹5 lakh, a 6-digit HSN is required; below that, 4 digits suffice.
Incorrect place of supply – this determines whether IGST or CGST/SGST applies.
Not mentioning the reverse charge liability – if you are liable to pay tax under reverse charge, you must state it.
Using the same serial number twice in a financial year – the number must be unique and sequential.
Rounding off tax amounts incorrectly – tax is rounded to the nearest rupee, but the total invoice value should be rounded consistently.
Forgetting to mention the IRN and QR code on e-invoices – without them, the recipient cannot claim ITC.

How to Correct an Invoice

If you make a mistake, you cannot simply erase it. You must issue a credit note or debit note. A credit note is issued when the invoice value is reduced or the supply is found to be deficient; a debit note is issued when the value is increased. Both must be issued within the time limit prescribed (usually by September of the following financial year or the date of filing the annual return, whichever is earlier). The credit note must be declared in the GST return, and it reduces the supplier’s tax liability and the recipient’s ITC.

Impact of Wrong Invoices on Input Tax Credit

The recipient can claim ITC only if they possess a valid tax invoice. If the invoice is missing any mandatory field, the recipient’s claim may be rejected. The supplier is also liable to pay a penalty under Section 122 of the CGST Act – up to ₹25,000 for issuing an incorrect invoice. In practice, the recipient often asks the supplier to reissue the invoice, which is not allowed for the same transaction; you must cancel the original and issue a new one with a different serial number.

Frequently Asked Questions

Is e-invoicing mandatory for B2C sales?

No, e-invoicing is mandatory only for B2B transactions and exports. However, for B2C invoices above ₹10,000, you must print a QR code that contains the invoice details, so that the recipient can verify it.

What happens if I don’t follow e-invoicing rules?

If you are required to e-invoice and don’t, the invoice is treated as not issued. The recipient cannot claim ITC, and you may face a penalty of up to ₹25,000 under Section 122. You may also be liable for interest on the tax that should have been paid.

Can I issue a consolidated invoice for multiple supplies?

Yes, you can issue a consolidated invoice for multiple supplies to the same recipient within a period of 24 hours, provided the total value does not exceed ₹5,000 (or ₹10,000 for certain cases). The consolidated invoice must contain all the required details.

Do I need to mention the HSN code on every invoice?

Yes, the HSN code is mandatory on all tax invoices. For supplies up to ₹5 lakh, a 4-digit HSN is sufficient; for supplies above ₹5 lakh, a 6-digit HSN is required. Some services use a service accounting code (SAC) instead.

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

A tax invoice is issued for taxable supplies, while a bill of supply is issued for exempt supplies or by composition dealers. A bill of supply does not contain tax amounts, but it must show the words “Bill of Supply” and the supplier’s details.

How do I correct a mistake in an e-invoice?

You cannot modify an e-invoice after it is registered on the IRP. You must cancel it within 24 hours and issue a new one with a different serial number. After 24 hours, you cannot cancel it; you must issue a credit note for the original and a new invoice for the corrected supply.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.