What is a GST Invoice?
A GST invoice (also called a Tax Invoice under GST) is a commercial document issued by a registered supplier for the supply of taxable goods or services. It serves as proof of sale, enables the buyer to claim Input Tax Credit (ITC), and is a key compliance document under the GST framework.
Issuing a proper GST invoice is mandatory for all registered taxpayers making taxable supplies. An invoice with missing mandatory fields can result in the buyer losing their ITC, and the supplier facing penalties.
GST Invoice Quick Facts:
- Mandatory for: All registered suppliers of taxable goods/services
- Not required for: Exempt supplies (issue Bill of Supply instead)
- Time limit: Goods — before/at delivery; Services — 30 days from supply date
- E-invoicing (IRP): Mandatory for businesses with turnover > Ôé╣5 crore
- Invoice serial number must be unique within a financial year
Mandatory Fields in a GST Tax Invoice
Under Rule 46 of CGST Rules, every GST tax invoice must contain the following information:
| # | Mandatory Field | Notes |
|---|---|---|
| 1 | Name, address, and GSTIN of supplier | Must match registration records |
| 2 | Nature of document (Tax Invoice) | Must be printed at top |
| 3 | Consecutive serial number (unique per FY) | Can contain letters, numbers, /, -, _ characters. Max 16 characters. |
| 4 | Date of issue | |
| 5 | Name, address, and GSTIN of recipient (B2B) | For B2C > Ôé╣2.5L: name and address; no GSTIN needed |
| 6 | HSN code of goods or SAC code of services | 2/4/6/8 digits depending on annual turnover |
| 7 | Description of goods or services | |
| 8 | Quantity and unit of measurement (for goods) | |
| 9 | Taxable value (after discounts) | |
| 10 | Rate of tax (CGST, SGST/UTGST, or IGST) | Show each rate separately |
| 11 | Tax amount (CGST, SGST/UTGST, or IGST) | Show each amount separately |
| 12 | Place of supply (state name and code) | Critical for determining IGST vs CGST+SGST |
| 13 | Address of delivery (if different from recipient address) | |
| 14 | Whether tax is payable on reverse charge basis | Write "Yes" or "No" |
| 15 | Signature or digital signature of supplier | Physical or digital |
CGST vs SGST vs IGST: When to Apply Which?
| Type of Supply | Tax Applied | Who Gets the Revenue |
|---|---|---|
| Intra-state supply (supplier and customer in same state) | CGST + SGST (each at half the total rate) | Centre (CGST) + State (SGST) |
| Inter-state supply (supplier and customer in different states) | IGST (at full rate) | Centre (shared with state later) |
| Import of goods/services | IGST + Customs duty | Centre |
| Export of goods/services | Zero-rated (0% GST or refund of ITC) | — |
Example: A supplier in Maharashtra sells to a buyer in Maharashtra. GST rate is 18% — so apply CGST 9% + SGST 9% (Maharashtra). If the buyer is in Delhi — apply IGST 18%.
HSN Code Requirements in GST Invoice
| Annual Aggregate Turnover | HSN Digits Required |
|---|---|
| Up to Ôé╣5 crore | 4-digit HSN code |
| Above Ôé╣5 crore | 6-digit HSN code |
| Export invoices | 8-digit HSN code (mandatory) |
Service providers use SAC (Services Accounting Code) — 6-digit codes for all service categories.
GST Invoice Format: Sample
TAX INVOICE Supplier Details: Invoice No.: INV-2025-001 [Your Business Name] Invoice Date: 15/06/2025 [Address] Place of Supply: Maharashtra (27) GSTIN: 27XXXXX0000X1ZX Bill To: Ship To (if different): [Customer Name] [Delivery Address] [Address] GSTIN: 27YYYYY0000Y1ZY +---------+------------+------+------+------------+------+------+------+--------+ | HSN/SAC | Description| Qty | Unit | Taxable Val| CGST | SGST | IGST | Total | +---------+------------+------+------+------------+------+------+------+--------+ | 8471 | Laptop | 2 | Nos | Ôé╣80,000 | 9% | 9% | — |Ôé╣94,400 | | | | | | |Ôé╣7,200|Ôé╣7,200| | | +---------+------------+------+------+------------+------+------+------+--------+ | Total | | | | Ôé╣80,000 |Ôé╣7,200|Ôé╣7,200| — |Ôé╣94,400 | +---------+------------+------+------+------------+------+------+------+--------+ Tax Amount in Words: Rupees Ninety Four Thousand Four Hundred Only Whether tax payable on reverse charge: No Authorised Signatory: _______________
GST Invoice vs Bill of Supply
| Feature | Tax Invoice | Bill of Supply |
|---|---|---|
| When issued | For taxable supplies | For exempt supplies or by composition dealers |
| Shows GST | Yes — CGST, SGST, or IGST shown separately | No — no GST charged |
| Buyer can claim ITC | Yes | No |
| Who issues | Regular GST taxpayers | Composition dealers + regular dealers for exempt goods |
Time Limit to Issue GST Invoice
| Type of Supply | Time Limit |
|---|---|
| Supply of goods (normal) | On or before delivery of goods |
| Supply of goods (continuous supply) | Before / at the time each statement of accounts is issued |
| Supply of services (normal) | Within 30 days of date of supply of service |
| Supply of services (banking / insurance / telecom) | Within 45 days |
| Reverse charge supply | Same day as date of supply |
E-Invoicing Under GST
E-invoicing is mandatory for businesses with aggregate annual turnover exceeding Ôé╣5 crore. Under e-invoicing:
- Invoices must be registered with the Invoice Registration Portal (IRP) — gst.gov.in IRP or GSTN-notified IRP
- IRP validates the invoice and generates a unique Invoice Reference Number (IRN) and QR code
- IRN and QR code must be printed on the physical invoice
- GSTR-1 is auto-populated from e-invoices — reduces manual data entry
- Buyers can verify invoice authenticity by scanning the QR code
Turnover threshold timeline:
- Ôé╣500 crore+ turnover: Mandatory since 1 October 2020
- Ôé╣100 crore+ turnover: Mandatory since 1 January 2021
- Ôé╣50 crore+ turnover: Mandatory since 1 April 2021
- Ôé╣20 crore+ turnover: Mandatory since 1 April 2022
- Ôé╣10 crore+ turnover: Mandatory since 1 October 2022
- Ôé╣5 crore+ turnover: Mandatory since 1 August 2023
Credit Note and Debit Note Under GST
When an invoice needs to be revised:
- Credit Note: Issued when taxable value or tax charged in the invoice is higher than what should have been charged (e.g., goods returned, discount given, price reduction). Reduces supplier's output tax and buyer's ITC.
- Debit Note: Issued when taxable value or tax charged is lower than what should have been (e.g., additional charges, price increase). Increases supplier's output tax.
- Credit/debit notes must be reported in GSTR-1 and GSTR-3B.
- Time limit: By September 30 of the next financial year or filing of annual return, whichever is earlier.
Common GST Invoice Mistakes
- Missing GSTIN of buyer: For B2B supplies, buyer's GSTIN is mandatory — without it, buyer cannot claim ITC
- Wrong place of supply: Determines CGST+SGST vs IGST — wrong classification means wrong tax collected
- Incorrect HSN/SAC code: Attracts wrong tax rate and penalties
- Not mentioning reverse charge: "Whether RCM applicable" must always appear
- Non-sequential numbering: Invoice numbers must be unique and sequential within a FY
- Issuing invoice after time limit: Late invoices attract penalty under Section 122
- Duplicate invoice numbers: Causes GSTR-1 filing errors and audit issues
Penalty for Not Issuing or Incorrect GST Invoice
- Penalty for non-issuance of invoice: Ôé╣10,000 per invoice or the amount of tax involved, whichever is higher
- Incorrect invoice (wrong GSTIN, wrong tax rate): Ôé╣10,000 or tax amount, whichever is higher
- E-invoicing non-compliance: Invoice treated as invalid; buyer cannot claim ITC on such invoices