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GST Invoice Format India: Complete Guide with Requirements (2026)

Last updated: March 22, 2026 • 8 min read

When India rolled out the Goods and Services Tax in July 2017, it replaced a patchwork of state and central taxes with a single, unified framework. The GST invoice became the foundational document of this system — a standardised record that links every supply of goods or services to a GSTIN, a tax rate, and a destination state. Get it right, and your client can claim their input tax credit seamlessly. Get it wrong, and that input tax credit gets blocked, creating friction, disputes, and potential compliance notices.

I have helped several small business owners and freelancers navigate their first GST invoices, and the most common problem I see is not a lack of effort — it is simply not knowing which fields are mandatory and why they exist. If you are looking for a broader overview of what a GST invoice is and who needs one, start with our guide to GST invoices for Indian businesses. This guide walks you through every requirement in plain language so you can create a fully compliant GST invoice without needing a CA on speed dial for every transaction.

What Is a GST Invoice?

A GST tax invoice is a document issued by a registered supplier of goods or services that records the transaction details required under the Central Goods and Services Tax (CGST) Act, 2017 and its state equivalents. It is the primary document for claiming Input Tax Credit (ITC) — the mechanism by which businesses offset the GST they pay on purchases against the GST they collect on sales. Without a valid tax invoice, the recipient cannot claim ITC, which means a poorly formatted invoice is a real financial problem for your client.

Who must issue a GST tax invoice? Any supplier registered under GST who makes a taxable supply of goods or services must issue a tax invoice. If you are a registered supplier selling exempt goods or services, or if you are a composition scheme taxpayer, you issue a "bill of supply" instead — a simpler document that does not show tax amounts because no GST is charged on the supply.

The distinction matters: a tax invoice is issued when GST is applicable and collectible. A bill of supply is issued when GST is not being charged — either because the supply is exempt or because the supplier is not collecting tax under the composition scheme.

The 16 Mandatory Fields on a GST Tax Invoice

Rule 46 of the CGST Rules, 2017 prescribes the minimum information that must appear on every GST tax invoice. These 16 fields are non-negotiable for B2B transactions and largely required for B2C as well.

1. Name, address and GSTIN of the supplier. Your full legal business name, registered address, and 15-digit GSTIN must appear prominently. The GSTIN encodes your state code, PAN, entity type, and a checksum digit — each part is verifiable by the recipient.
2. "Tax Invoice" heading. The document must be clearly titled "Tax Invoice." This is not optional — omitting this label or using a generic title like "Invoice" creates ambiguity about the document type.
3. A consecutive serial number. The invoice number must be consecutive and unique within a financial year. It can contain letters, numerals, and certain special characters, but it cannot exceed 16 characters. More on the format rules below.
4. Date of issue. The date on which the invoice is issued. This is not necessarily the delivery date — it is the date you create and issue the invoice, subject to the time limits discussed later.
5. Name and address of the recipient. The billing name and address of your customer. For B2B supplies, this should match the registered business name associated with the recipient's GSTIN.
6. GSTIN of the recipient (for taxable B2B supplies). If your customer is GST-registered, their GSTIN must appear on the invoice. This is what allows them to claim ITC. For B2C supplies where the recipient is unregistered, this field is not required — but for inter-state B2C supplies above ₹2.5 lakh, the recipient's state name and state code must be mentioned instead.
7. Place of supply. The state in which the supply is deemed to have occurred under GST law. This determines whether CGST+SGST or IGST applies. It is not always the physical delivery location — for services, the place of supply rules are more nuanced and depend on the nature of the service.
8. HSN code (for goods) or SAC code (for services). The Harmonised System of Nomenclature (HSN) code for goods or the Service Accounting Code (SAC) for services classifies what is being supplied. The number of digits required depends on your annual turnover — businesses with turnover above ₹5 crore must use 6-digit HSN codes; those between ₹1.5 crore and ₹5 crore must use 4-digit codes; those below ₹1.5 crore are exempt from HSN codes on invoices (though it is good practice to include them).
9. Description of goods or services. A clear description of what is being supplied. This does not need to be exhaustive, but it must be specific enough to identify the goods or service and match the HSN/SAC classification.
10. Quantity and unit of measurement (for goods). The quantity supplied and the unit — kilograms, litres, pieces, metres, etc. For services, quantity may not always be applicable, but hours, units, or a fixed engagement description should be used.
11. Total value of supply. The aggregate value of the goods or services before tax. If any discounts apply, they should be stated separately.
12. Taxable value after adjustments. The value on which GST is calculated. If there are discounts or abatements, the taxable value will differ from the total value.
13. Rate of tax (CGST, SGST/UTGST, or IGST). The applicable GST rate for each line item. Common rates are 5%, 12%, 18%, and 28%. Each rate must be stated explicitly — showing only the total percentage is not sufficient; the component breakdown is required.
14. Amount of tax (CGST, SGST/UTGST, or IGST). The actual rupee amount of tax for each component. For intra-state supplies, show CGST and SGST separately (each at half the total rate). For inter-state supplies, show IGST as a single amount at the full rate.
15. Place of delivery (if different from place of supply). For goods, if the delivery address differs from the billing address and the place of supply, it must be stated.
16. Signature or digital signature of the supplier. The invoice must be authenticated by the supplier or their authorised representative. A digital signature is acceptable and is mandatory for e-invoices.

CGST vs SGST vs IGST Explained

One of the most confusing aspects of GST for new registrants is understanding which tax applies to which transaction. The rule is straightforward once you know the logic: GST is split between the central government and state governments, and the split depends entirely on whether the transaction is within one state or crosses state lines.

Intra-state supply: CGST + SGST

When the supplier and the place of supply are in the same state, Central GST (CGST) and State GST (SGST) both apply, each at half the total rate. For example: a web developer based in Mumbai (Maharashtra) invoices a client whose place of supply is also in Maharashtra. If the applicable GST rate is 18%, the invoice shows CGST at 9% and SGST at 9% — each applied to the taxable value separately. The total tax burden is still 18%, but it is split equally between the central and state governments.

Inter-state supply: IGST

When the supplier and the place of supply are in different states, Integrated GST (IGST) applies at the full rate as a single charge. Using the same example: if that Mumbai-based web developer invoices a client whose place of supply is Bengaluru (Karnataka), the invoice shows IGST at 18% on the taxable value. The central government collects this IGST and then transfers the state's share to Karnataka. The client in Karnataka can claim ITC on the full IGST amount paid.

This means the correct tax type on your invoice is not a matter of preference — it is determined by geography. Getting this wrong (charging CGST+SGST on an inter-state transaction, for instance) is one of the most common and consequential GST invoice errors, because it affects which government receives the tax and blocks the recipient's ITC claim. For a broader look at tax compliance across GST, VAT, and sales tax systems, see our tax compliance guide for small businesses.

Invoice Number Format for GST

The GST invoice number must follow specific rules under Rule 46 of the CGST Rules. It must be consecutive and unique within a financial year (April 1 to March 31). It can include alphabets, numerals, and the special characters hyphen (-) and forward slash (/). It cannot contain spaces, and it cannot exceed 16 characters in length.

Practical formats that work well: INV/2526/001 (financial year 25-26, invoice 001), 2526-001, or ABC/2526/0001 (where ABC is an abbreviation for your business). The financial year reference in the number is not legally required but is strongly recommended — it makes your records self-documenting and avoids confusion when sequence numbers reset each year.

You must reset your sequence at the start of each new financial year. Running a single continuous sequence across multiple financial years is not compliant. Each financial year gets its own sequential series starting from 001 (or 0001, or 1 — the format is your choice as long as it is consistent and consecutive).

Time Limit to Issue a GST Invoice

The CGST Act prescribes strict time limits for issuing invoices. Missing these deadlines can result in compliance issues and disputes over ITC eligibility.

For goods: A tax invoice must be issued at or before the time of removal of goods (for movable goods) or at the time of delivery (for immovable goods). In practice, this means the invoice must be issued when you dispatch or deliver the goods — you cannot wait until later in the month.

For services: The invoice must be issued within 30 days of the date of supply of services. For banking and financial institutions, this window extends to 45 days. For most service providers — consultants, designers, developers, writers — the 30-day rule applies.

E-Invoicing Requirements

E-invoicing under GST does not mean sending invoices by email. It is a specific government-mandated process in which invoice data is reported to the Invoice Registration Portal (IRP) before the invoice is issued to the buyer. The IRP validates the data, assigns a unique Invoice Reference Number (IRN), and generates a QR code that must be printed on the invoice.

Who must comply with e-invoicing? As of April 2023, all GST-registered businesses with aggregate turnover exceeding ₹5 crore in any financial year since 2017-18 must generate e-invoices for all B2B transactions, exports, and supplies to SEZs. The ₹5 crore threshold has been progressively lowered from the original ₹500 crore limit since the system launched — check the current threshold on the GST portal as it may be revised further.

What does e-invoicing involve in practice? You (or your billing software) submit the invoice data to the IRP in a standardised JSON format. The IRP validates the GSTIN details, checks for duplicate IRNs, and returns the IRN and a digitally signed QR code — typically within seconds. The QR code embeds key invoice details and allows tax authorities and recipients to verify the invoice's authenticity by scanning it. A physical or digital copy of the invoice with the IRN and QR code is then issued to the buyer.

Businesses not covered by e-invoicing can still create compliant invoices using tools like InvoiceGen and do not need to interact with the IRP.

Common GST Invoice Mistakes

Incorrect or missing GSTIN. Transposing digits in a GSTIN or using an old GSTIN after re-registration is one of the most common errors. Always verify the recipient's GSTIN on the official GST portal before issuing an invoice — it takes thirty seconds and prevents significant downstream problems.

Wrong place of supply. As explained above, the place of supply determines whether CGST+SGST or IGST applies. Getting this wrong means the wrong tax authority receives the revenue, and the recipient's ITC claim may be blocked. This is particularly easy to get wrong for services where the place of supply rules are complex.

Missing HSN/SAC code. Many businesses omit HSN or SAC codes, especially on service invoices. If your turnover requires you to include them (above ₹1.5 crore), a missing code makes the invoice technically non-compliant and can trigger notices during scrutiny.

Charging the wrong tax type. Charging CGST+SGST on an inter-state transaction (or IGST on an intra-state one) creates a mismatch in the tax records that is difficult to correct after filing. Double-check the location of your customer's place of supply before determining the tax type.

Not including "Tax Invoice" as the document title. This sounds trivial, but it is a mandatory requirement. Using "Invoice," "Sales Invoice," or just your business name as the document header makes the document type ambiguous.

Exceeding the 16-character invoice number limit. Longer invoice numbers that include full dates, client names, and sequential numbers can easily exceed 16 characters. Keep your numbering format short and structured.

How to Create a GST Invoice for Free Using InvoiceGen

You do not need expensive accounting software to create a GST-compliant invoice. InvoiceGen lets you build a complete, properly formatted invoice in under two minutes — directly in your browser, with no account required.

Enter your business name, address, and GSTIN. Add your client's details and GSTIN. Choose whether to apply CGST+SGST (intra-state) or IGST (inter-state) and set the applicable rate. Add your line items with HSN/SAC codes, descriptions, and amounts. The tool calculates all tax components automatically. When you are done, download a clean PDF that meets all the formatting requirements under the CGST Act.

For businesses not yet required to e-invoice, this covers everything you need. For those within the e-invoicing mandate, you will still need to submit the data to the IRP separately and add the returned IRN and QR code to the final document — but starting with a properly structured invoice makes that process significantly smoother.