A GST invoice isn’t just a payment request — it’s a legal document. If it’s missing even one mandatory field, your client can’t claim Input Tax Credit (ITC), which means disputes, payment delays, and compliance headaches for both sides.
Here’s the complete list of what every GST invoice must include.
Who Needs to Issue a GST Invoice?
Every GST-registered business must issue a proper tax invoice when:
- Supplying goods or services to another GST-registered business (B2B)
- The transaction value exceeds ₹200 for unregistered buyers (B2C)
- Making inter-state supplies, regardless of value
If you’re not GST-registered, you issue a regular commercial invoice — not a tax invoice. You cannot charge GST if you’re unregistered.
The 16 Mandatory Fields on a GST Invoice
Under Section 31 of the CGST Act and Rule 46 of CGST Rules, a tax invoice must contain:
1. Name, Address, and GSTIN of the Supplier
Your registered business name exactly as it appears in your GST registration. Your GSTIN must be present.
2. A Consecutive Serial Number
Each invoice must have a unique serial number within a financial year. It can contain letters, numbers, and special characters like / or -. It cannot exceed 16 characters.
Example: ISN-2026-0001, PB/2025-26/001
3. Date of Issue
The date the invoice is raised. For goods, the invoice must be issued at the time of supply. For services, within 30 days of supply (45 days for banks and NBFCs).
4. Name, Address, and GSTIN of the Recipient (for B2B)
For registered buyers, their GSTIN is mandatory. For unregistered buyers, name and address are required if the transaction value exceeds ₹50,000.
5. HSN Code or SAC Code
- HSN (Harmonised System of Nomenclature): For goods
- SAC (Services Accounting Code): For services
The number of digits required depends on your annual turnover:
| Annual Turnover | HSN Digits Required |
|---|---|
| Up to ₹5 crore | 4 digits |
| Above ₹5 crore | 6 digits |
| Exports | 8 digits |
6. Description of Goods or Services
A clear description of what is being supplied. Vague descriptions like “services rendered” are not acceptable.
7. Quantity (for Goods)
The quantity and unit of measurement (e.g., kg, pcs, litres, hours).
8. Total Value of Supply
The total value before any discount.
9. Taxable Value
The value on which GST is calculated — after deducting discounts, if any.
10. Applicable GST Rate
The GST rate applied: 5%, 12%, 18%, or 28%.
11. Amount of GST Charged
Broken down as:
- CGST + SGST for intra-state supplies (same state)
- IGST for inter-state supplies or exports
Both the rate and the amount must be shown separately.
12. Place of Supply
The state where the supply is deemed to have taken place. This determines whether CGST+SGST or IGST applies.
13. Whether Tax is Payable on Reverse Charge
If the transaction falls under Reverse Charge Mechanism (RCM), this must be stated explicitly on the invoice.
14. Signature or Digital Signature of the Supplier
The invoice must be signed by the supplier or an authorised representative. A digital signature is acceptable.
15. Shipping Address (if different from billing address)
For goods delivered to a different location than the billing address, the delivery address must be included.
16. For Exports: Additional Fields
- Shipping bill number and date
- Port code
- Statement: “Supply meant for export on payment of IGST” or “Supply meant for export under bond/LUT without payment of IGST”
Common Mistakes That Make an Invoice Non-Compliant
Wrong GSTIN. A single character error in your GSTIN or your client’s GSTIN makes the invoice invalid for ITC purposes.
Missing HSN/SAC code. Many small businesses skip this entirely. It’s mandatory.
Invoice date after the supply date. For goods, you cannot backdate or forward-date an invoice. It must be issued at the time of supply.
Rounding GST incorrectly. GST must be calculated on the taxable value, not the total. Rounding must follow standard rounding rules.
No place of supply mentioned. Without this, it’s unclear whether CGST+SGST or IGST applies — which can cause ITC mismatches.
Serial numbers not unique within the year. Each financial year must have a fresh series. You cannot reuse invoice numbers.
Formats That Are Acceptable
The GST law does not mandate a specific template or software. Your invoice can be:
- Generated by invoicing software
- A printed format
- Handwritten (for certain categories)
- An e-Invoice (mandatory for businesses above ₹5 crore turnover)
What matters is that all mandatory fields are present and the information is accurate.
e-Invoicing: Is It Mandatory for You?
From August 2023, e-invoicing under the IRP (Invoice Registration Portal) is mandatory for businesses with annual turnover above ₹5 crore. Below that threshold, it remains optional but recommended.
e-Invoices are validated by the government portal and assigned an IRN (Invoice Reference Number) and QR code — which then also appear on the invoice.
Invoicing System generates fully GST-compliant invoices with all mandatory fields — CGST/SGST/IGST split automatically based on your client’s state, HSN/SAC codes, and proper serial numbering. Free for Indian SMEs. Get started →