The tax invoice is the most important document in GST. It proves the supply, fixes the time of supply for goods, and is the document the buyer needs to claim input tax credit. An invoice issued late or missing a mandatory detail can cost the buyer its credit, which is why both exam questions and auditors focus on it.
When to issue a tax invoice
| Supply | Time limit |
|---|---|
| Goods involving movement | Before or at the time of removal for supply |
| Goods without movement | Before or at the time of delivery or making available to the recipient |
| Continuous supply of goods | Before or at the time each statement is issued or each payment is received |
| Services | Within 30 days of the date of supply |
| Services by insurers, banks, financial institutions and NBFCs | Within 45 days of the date of supply |
| Goods sent on approval (sale or return) | Before or at the time of supply, or 6 months from removal, whichever is earlier |
What a tax invoice must contain (rule 46)
- Name, address and GSTIN of the supplier.
- A consecutive serial number of up to 16 characters, unique for the financial year.
- Date of issue.
- Name, address and GSTIN of a registered recipient. For an unregistered recipient, name, address and delivery address with the State name and code when the taxable value is ₹50,000 or more.
- HSN code for goods or SAC for services: 4 digits on B2B invoices if aggregate turnover in the preceding year is up to ₹5 crore, and 6 digits above ₹5 crore.
- Description, quantity, total value, taxable value after discounts, tax rate and amount for each tax (CGST, SGST, UTGST, IGST, cess).
- Place of supply with the State name, for inter-State supplies.
- Address of delivery, if different from the place of supply.
- Whether tax is payable on reverse charge.
- Signature or digital signature of the supplier or authorised representative.
Invoices for goods are made in triplicate (original for the recipient, duplicate for the transporter, triplicate for the supplier) and for services in duplicate.
E-invoicing
An e-invoice is not an invoice generated by the Government. The supplier creates the invoice in its own system and uploads its details to an Invoice Registration Portal (IRP), which returns an Invoice Reference Number (IRN), a digital signature and a QR code. The details then flow automatically into GSTR-1 and the e-way bill.
- Who must issue e-invoices: registered persons whose aggregate turnover exceeded ₹5 crore in any financial year from 2017-18 onwards.
- For which supplies: B2B supplies and exports, including supplies on which the recipient pays tax under reverse charge. Not for B2C supplies, imports, or supplies received from unregistered persons.
- Exempt entities, whatever their turnover: SEZ units; insurers, banking companies and financial institutions including NBFCs; GTAs; suppliers of passenger transport services; multiplexes for cinema admission; and Government departments and local authorities.
- Supplies to Government departments registered only for TDS count as B2B, so an e-invoice is needed if the supplier is above the threshold.
Dynamic QR code: registered persons whose aggregate turnover exceeds ₹500 crore must put a dynamic QR code on B2C invoices, so customers can scan and pay in one step.
From practice
In a company above the threshold, the invoice is not complete until the IRN is generated, so the ERP typically blocks printing or dispatch until the IRP responds. A buyer that receives an invoice without a valid IRN from such a supplier should not claim credit on it until it is regularised. In an ICAI example, a firm of advocates with turnover above ₹5 crore must still issue an e-invoice for legal services to a business, even though the client pays the GST under reverse charge.
Quick check
Why
Insurers, banking companies, financial institutions and NBFCs have 45 days from the date of supply to issue the invoice. Other service providers have 30 days.
Quick check
Why
The manufacturer is a notified person making B2B supplies. SEZ units, GTAs and multiplexes are among the entities exempt from e-invoicing whatever their turnover.
Exam lens
Questions on invoice timing are quick marks: identify goods or services, then the category of supplier, then quote the time limit with the provision. For e-invoicing questions, check the exemption list before the ₹5 crore test.
Frequently asked questions
What is the time limit to issue a tax invoice for services?
Within 30 days of the date of supply, or 45 days for insurers, banking companies, financial institutions and NBFCs.
Who needs to generate e-invoices?
Registered persons whose aggregate turnover exceeded ₹5 crore in any financial year from 2017-18, for B2B supplies and exports, unless they are in an exempt category.
Is e-invoicing required for B2C supplies?
No. But businesses with aggregate turnover above ₹500 crore must show a dynamic QR code on B2C invoices.
Related reading
- Time of supply under GST: sections 12 and 13
- Input tax credit conditions under section 16
- E-way bill under GST: limit, validity and who generates it
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Note
Based on Chapter 10 (Tax Invoice, Credit and Debit Notes) of the ICAI BoS Study Material, Intermediate Paper 3 Section B, for May 2027, September 2027 and January 2028 (law as amended up to 30.04.2026). Last reviewed 15 October 2026.