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Commercial & GST8 min read•Verified: Current CBIC GST Rule Standards

GST Tax Invoice Guide: Mandatory Fields, Rule 46 Compliance & HSN/SAC Rules

Comprehensive guide to creating compliant GST tax invoices under Rule 46 of CGST Rules 2017. Learn mandatory fields, CGST/SGST/IGST splits, and common invoicing mistakes.

Key Takeaways at a Glance
  • A GST Tax Invoice is a legal commercial document governed by Section 31 of the CGST Act, 2017 read with Rule 46 of the CGST Rules, 2017.
  • A valid tax invoice must contain at least 16 statutory particulars, including seller/buyer GSTIN, unique consecutive serial number, HSN/SAC code, and tax split.
  • The determination of tax type depends on Place of Supply (PoS): Intra-state supplies (supplier and PoS in the same State) attract CGST + SGST; inter-state supplies attract IGST.
  • Composition scheme dealers and suppliers of wholly exempt goods cannot issue a Tax Invoice; they are legally required to issue a "Bill of Supply" with no GST charged to the recipient.
  • HSN reporting requirements mandate 4 digits for turnover up to ₹5 Crore (B2B supply) and 6 digits for turnover exceeding ₹5 Crore for all supplies.

1. What is a GST Tax Invoice under Indian Law?

Under Section 31 of the Central Goods and Services Tax (CGST) Act, 2017, every registered person supplying taxable goods or services must issue a Tax Invoice showing the description, quantity, value of goods, tax charged thereon, and other prescribed particulars. A tax invoice is not merely an accounting record—it is the indispensable legal instrument that enables a registered buyer to claimInput Tax Credit (ITC) under Section 16 of the CGST Act.

2. Mandatory Fields for a Valid Tax Invoice (Rule 46 Checklist)

Under Rule 46 of the CGST Rules, 2017, an invoice must contain the following statutory particulars to be legally compliant:

1. Supplier Details

Legal name, registered trade name, physical address, and 15-digit GSTIN of the supplier.

2. Consecutive Serial Number

Unique consecutive invoice number (max 16 characters), containing letters, numbers, or hyphens/slashes, unique for each FY.

3. Date of Issue

Exact date on which the invoice is issued (must precede or coincide with delivery of goods/services).

4. Recipient Details

Name, address, and GSTIN / UIN of the registered recipient. For unregistered buyers, address is required if value > ₹50,000.

5. HSN or SAC Classification

Harmonized System of Nomenclature (HSN) for goods or Services Accounting Code (SAC) for services (see digit rules below).

6. Place of Supply & State Code

Name of the State and its official 2-digit GST state code where the supply is delivered.

7. Taxable Value & Tax Split

Taxable value after discounts, followed by itemized CGST + SGST (intra-state) or IGST (inter-state) amounts.

8. Reverse Charge & Signature

Whether tax is payable on reverse charge basis (Yes/No), and physical or digital signature of the authorized signatory.

3. Intra-State vs Inter-State Supply: How to Split GST

The most critical operational determination when raising an invoice is comparing the Location of the Supplier against the Place of Supply (PoS):

Intra-State Supply

Supplier State = Place of Supply

When the seller and delivery location are in the same State or UT (e.g. Mumbai seller to Pune buyer).

Charge: 50% CGST + 50% SGST (e.g. 9% + 9% for 18% slab)
Inter-State Supply

Supplier State ≠ Place of Supply

When the seller and delivery location are in different States or UTs (e.g. Bengaluru seller to Hyderabad buyer).

Charge: 100% IGST (e.g. 18% Integrated GST)

4. HSN/SAC Digit Rules (CBIC Notification No. 78/2020)

Businesses must classify goods using Harmonized System of Nomenclature (HSN) and services using Services Accounting Code (SAC). The number of required digits depends on annual turnover:

Aggregate Annual TurnoverB2B InvoicesB2C Invoices
Up to ₹5 CroreMinimum 4 DigitsOptional (4 Digits recommended)
Exceeding ₹5 CroreMandatory 6 DigitsMandatory 6 Digits

5. Common GST Invoicing Errors That Disallow Buyer ITC

Levying CGST/SGST instead of IGST on Inter-State Supply: If the buyer is in Karnataka and the supplier is in Maharashtra, charging CGST+SGST violates Section 7 of the IGST Act. The buyer cannot claim ITC on improper tax headers.
Duplicate Invoice Numbers: Using non-consecutive series or restarting numbers within the same financial year triggers mismatches in GSTR-1 filings.
Issuing a Tax Invoice as a Composition Dealer: Composition taxpayers cannot charge GST or issue Tax Invoices; they must issue a “Bill of Supply” bearing the phrase “Composition taxable person, not eligible to collect tax on supplies”.
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Frequently Asked Questions

What is the key difference between a Tax Invoice and a Bill of Supply under GST?▼

A Tax Invoice is issued by a regular registered GST dealer when charging output GST on taxable supplies, allowing the buyer to claim Input Tax Credit (ITC). A Bill of Supply is issued by composition scheme taxpayers or suppliers of wholly exempt goods, where no tax is charged and no ITC can be claimed by the recipient.

How do I determine whether to charge CGST + SGST or IGST on an invoice?▼

This depends on the Place of Supply (PoS) relative to the supplier’s location. If the supplier’s registered business address and the Place of Supply are within the same Indian state or Union Territory, the supply is intra-state and attracts equal parts CGST and SGST (e.g., 9% + 9% for an 18% item). If the PoS is in a different state, the supply is inter-state and attracts IGST (18%).

What are the rules for numbering GST invoices under Rule 46(b)?▼

Invoices must contain a consecutive serial number not exceeding 16 characters, in one or multiple series, containing alphabets, numerals, and special characters (hyphen "-" or slash "/" only). The series must be unique for each Financial Year (e.g., INV/2024-25/001).

How many digits of HSN/SAC code must be mentioned on a tax invoice?▼

As per CBIC Notification No. 78/2020: Registered taxpayers with aggregate annual turnover up to ₹5 Crore must mention at least 4 digits of HSN for B2B supplies (optional for B2C supplies). Taxpayers with aggregate turnover above ₹5 Crore must mention 6 digits of HSN on all B2B and B2C invoices.

Authoritative Sources & References