If you’re running a freelance business or managing an SMB in India, you’ve probably wondered: What exactly needs to be on a GST invoice? Getting this wrong can lead to rejected invoices, compliance issues, and penalties from the GST department.
This guide covers every mandatory field required in a GST invoice in India—with real examples, practical scenarios, and a checklist you can use right now.
Let’s dive in.
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What Are Mandatory Fields in a GST Invoice?
The GST law (CGST/SGST Rules) specifies exactly which fields must appear on every GST invoice. These aren’t suggestions—they’re legal requirements under the IGST Act and GST Compensation Cess Rules.
Missing even one field can make your invoice non-compliant, which means:
– Your customer can’t claim Input Tax Credit (ITC)
– You’re exposed to penalties
– Audit flags become more likely
There are 16 mandatory fields that every GST invoice must contain. Some are basic (like invoice number), while others are more detailed (like HSN/SAC codes and tax breakdowns).
Key Takeaway: A compliant GST invoice includes 16 mandatory fields—skip any one, and your invoice loses legal validity.
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The 16 Mandatory Fields in GST Invoice: Complete List
Here’s the exact breakdown of what must appear on every GST invoice in India:
1. Invoice Number (Unique Identifier)
This is a sequential number assigned to each invoice. It must be unique within your financial year and can’t repeat.
– Format example: INV-2024-001, GST-001, etc.
– Must be sequential (you can’t skip numbers)
– If you’re issuing a credit/debit note, it gets a separate numbering series
2. Invoice Date
The date when the invoice is issued. This is critical because:
– GST is calculated based on this date
– It determines which GST rate applies (rates change periodically)
– It affects tax payment deadlines
Format: DD/MM/YYYY (e.g., 15/01/2024)
3. Supplier’s Details (Your Company Information)
Your business must list:
– Legal name (as registered with GST)
– GSTIN (16-digit GST Identification Number)
– Address (registered office address)
– State code (two-letter state identifier)
– Email and phone (contact details)
Real Example:
“`
ABC Freelance Services Pvt Ltd
GSTIN: 27ABCDE1234F1Z5
Bangalore, Karnataka 560034
Phone: +91-98765-43210
Email: info@abcfreelance.com
“`
4. Recipient’s Details (Your Customer’s Information)
Similarly, you must include your customer’s:
– Legal name
– GSTIN (if they’re GST-registered; if not, write “UNREGISTERED”)
– Address and state code
– Contact details
Note: If your customer is not GST-registered (like a retail customer), you still mention they’re unregistered, but you can’t charge GST.
5. Place of Supply
This tells the GST department in which state the supply is being made. This is critical because:
– It determines whether CGST + SGST or IGST applies
– If supply is in the same state → use CGST + SGST
– If supply is interstate → use IGST
Real Example:
If you’re based in Delhi and providing services to a company in Mumbai, the place of supply is Maharashtra (the customer’s location).
6. HSN/SAC Code
This is the product/service classification code:
– HSN = Harmonized System of Nomenclature (for goods)
– SAC = Service Accounting Code (for services)
Every product and service has a specific code that determines the GST rate.
Real Example:
– Freelance writing services → SAC code 9983 (GST rate: 18%)
– Website design services → SAC code 9983 (GST rate: 18%)
– Software consultancy → SAC code 9983 (GST rate: 18%)
7. Description of Goods/Services
A clear, detailed description of what you’re selling or the service you’re providing.
Real Example (Freelancer):
“`
Writing 5 blog posts (1000 words each) on digital marketing
for website optimization project (Jan 15-20, 2024)
“`
8. Unit of Measurement
How are you measuring the supply? By:
– Quantity (units)
– Hours (for services)
– Days (for project-based work)
– Per page, per word, per project, etc.
9. Quantity
The number of units you’re supplying.
Real Example:
– 500 words of content = 500
– 40 hours of consulting = 40
– 1 website = 1
10. Unit Price (Without GST)
The per-unit price before GST is added.
Real Example:
If you’re charging ₹100 per hour for 40 hours:
– Unit Price = ₹100/hour
11. Taxable Value
The total value before GST.
Formula: Quantity × Unit Price
Real Example:
40 hours × ₹100/hour = ₹4,000 (taxable value)
12. GST Rate Applicable
The percentage of GST that applies to your product/service. This varies:
– 0% (exempted items)
– 5% (essentials like food)
– 12% (some goods and services)
– 18% (most services, including freelancing)
– 28% (luxury items)
Real Example:
Freelance writing = 18% GST
13. CGST Amount (Central GST)
Half of the GST rate when the supply is intra-state (same state).
Formula: Taxable Value × (GST Rate ÷ 2)
Real Example:
₹4,000 × (18% ÷ 2) = ₹4,000 × 9% = ₹360 CGST
14. SGST Amount (State GST)
The other half of the GST rate when the supply is intra-state.
Formula: Taxable Value × (GST Rate ÷ 2)
Real Example:
₹4,000 × (18% ÷ 2) = ₹4,000 × 9% = ₹360 SGST
Note: If it’s interstate, there’s no CGST/SGST. Instead, you use IGST (Integrated GST) = Full GST rate.
15. Invoice Amount (Total Invoice Value)
The final amount your customer pays.
Formula: Taxable Value + CGST + SGST (or Taxable Value + IGST)
Real Example:
₹4,000 + ₹360 + ₹360 = ₹4,720
16. Signature or Digital Signature
A physical or digital signature of the authorized person from your company.
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Mandatory Fields in GST Invoice: Table Comparison
Here’s a quick reference table showing which fields are mandatory vs. optional:
| Field | Mandatory? | For Goods | For Services | Notes |
|——-|———–|———–|————–|——-|
| Invoice Number | ✅ Yes | ✅ | ✅ | Must be sequential and unique |
| Invoice Date | ✅ Yes | ✅ | ✅ | Determines GST applicability |
| Supplier GSTIN | ✅ Yes | ✅ | ✅ | 16-digit identifier |
| Supplier Address | ✅ Yes | ✅ | ✅ | Registered office address |
| Recipient GSTIN/Status | ✅ Yes | ✅ | ✅ | Mark as “Unregistered” if needed |
| Recipient Address | ✅ Yes | ✅ | ✅ | Customer’s address |
| Place of Supply | ✅ Yes | ✅ | ✅ | Determines CGST+SGST or IGST |
| HSN/SAC Code | ✅ Yes | ✅ | ✅ | Product/service classification |
| Description | ✅ Yes | ✅ | ✅ | Clear details of supply |
| Unit | ✅ Yes | ✅ | ✅ | Units, hours, pages, etc. |
| Quantity | ✅ Yes | ✅ | ✅ | Number of units |
| Unit Price (Excl. Tax) | ✅ Yes | ✅ | ✅ | Price before GST |
| Taxable Value | ✅ Yes | ✅ | ✅ | Quantity × Unit Price |
| GST Rate | ✅ Yes | ✅ | ✅ | 0%, 5%, 12%, 18%, or 28% |
| Tax Amount (CGST/SGST/IGST) | ✅ Yes | ✅ | ✅ | Calculated automatically |
| Total Invoice Amount | ✅ Yes | ✅ | ✅ | Taxable Value + Tax |
| Signature | ✅ Yes | ✅ | ✅ | Physical or digital |
Key Takeaway: All 16 fields are mandatory for both goods and services; none are truly optional under GST law.
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GST Invoice Mandatory Fields for Freelancers: Practical Scenarios
Let’s look at how these mandatory fields work in real freelancer situations.
Scenario 1: Freelance Writer in Delhi (Intra-State Supply)
Client Details:
– You: Freelance Writer (Delhi, GSTIN: 07XXXXX1234Z5)
– Client: ABC Marketing Company (Delhi, GSTIN: 07YYYYY5678Z9)
– Service: 5 blog posts (1000 words each) on digital marketing
– Rate: ₹200/per 100 words
Invoice Breakdown:
“`
Invoice Number: FW-2024-001
Invoice Date: 15/01/2024
FROM: Your Name (Freelancer)
GSTIN: 07XXXXX1234Z5
Delhi, 110001
TO: ABC Marketing Company
GSTIN: 07YYYYY5678Z9
Delhi, 110001
—
Description: Writing 5 blog posts (1000 words each) on digital marketing
HSN/SAC: 9983 (Freelance Writing Services)
Quantity: 5,000 words
Unit: Per 100 words
Unit Price: ₹200
Taxable Value: 5,000/100 × ₹200 = ₹10,000
GST Rate: 18%
CGST (9%): ₹10,000 × 9% = ₹900
SGST (9%): ₹10,000 × 9% = ₹900
TOTAL INVOICE: ₹10,000 + ₹900 + ₹900 = ₹11,800
“`
Why CGST + SGST? Because both the supplier and recipient are in the same state (Delhi).
Scenario 2: Freelance Developer (Interstate Supply)
Client Details:
– You: Web Developer (Bangalore, GSTIN: 29XXXXX9876Z5)
– Client: Tech Startup (Mumbai, GSTIN: 27YYYYY4321Z9)
– Service: Website development (30 hours)
– Rate: ₹1,500/hour
Invoice Breakdown:
“`
Invoice Number: WD-2024-045
Invoice Date: 20/01/2024
FROM: Your Name (Freelancer)
GSTIN: 29XXXXX9876Z5
Bangalore, 560034
TO: Tech Startup
GSTIN: 27YYYYY4321Z9
Mumbai, 400001
—
Description: Website development & testing for e-commerce platform
HSN/SAC: 9983 (Web Design/Development Services)
Quantity: 30 hours
Unit: Hours
Unit Price: ₹1,500
Taxable Value: 30 × ₹1,500 = ₹45,000
GST Rate: 18%
IGST (18%): ₹45,000 × 18% = ₹8,100
TOTAL INVOICE: ₹45,000 + ₹8,100 = ₹53,100
“`
Why IGST? Because the supplier (Bangalore) and recipient (Mumbai) are in different states. IGST replaces CGST + SGST.
Scenario 3: Freelancer with Unregistered Customer
Client Details:
– You: Content Creator (Hyderabad, GSTIN: 36XXXXX6543Z5)
– Client: Small local retail shop (Unregistered under GST)
– Service: Social media content creation (10 posts)
– Rate: ₹500/post
Invoice Breakdown:
“`
Invoice Number: CM-2024-012
Invoice Date: 25/01/2024
FROM: Your Name (Content Creator)
GSTIN: 36XXXXX6543Z5
Hyderabad, 500001
TO: XYZ Retail Shop
GSTIN: UNREGISTERED
Hyderabad, 500001
—
Description: Creating 10 Instagram posts with captions & hashtags
HSN/SAC: 9983 (Content Creation Services)
Quantity: 10 posts
Unit: Posts
Unit Price: ₹500
Taxable Value: 10 × ₹500 = ₹5,000
GST Rate: 18%
CGST (9%): ₹5,000 × 9% = ₹450
SGST (9%): ₹5,000 × 9% = ₹450
TOTAL INVOICE: ₹5,000 + ₹450 + ₹450 = ₹5,900
“`
Important: Even though the customer is unregistered, you still charge GST. The customer can’t claim ITC, but you must pay the GST to the government.
Key Takeaway: The mandatory fields remain the same across all scenarios, but CGST+SGST vs. IGST changes based on whether the supply is within the same state or interstate.
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Common Mistakes When Creating Mandatory Fields in GST Invoices
Here are the most common errors we see freelancers and small businesses make:
Mistake 1: Wrong HSN/SAC Code
Many freelancers use the wrong SAC code, which can trigger audit flags.
Correct SAC codes for common services:
– Freelance writing, translation, content creation: 9983
– Web design and development: 9983
– Graphic design and photography: 9983
– Accounting and bookkeeping: 9982
– Consulting (general): 9983
– Training and coaching: 9983
Real Example of Mistake:
A freelancer mistakenly used SAC 9950 (postal/courier) instead of 9983 (professional services). This mismatch can cause invoice rejection.
Mistake 2: Missing Place of Supply
Many freelancers from Tier-2 cities assume the place of supply is their own location. It’s not—it’s the customer’s location.
Correct Logic:
– Customer in same state = CGST + SGST
– Customer in different state = IGST
Mistake 3: Incorrect Tax Calculation
A common error is rounding off GST amounts incorrectly. GST must be calculated on the taxable value, not rounded mid-way.
Wrong Calculation:
Taxable Value: ₹10,000
– Rounding CGST: ₹910 (incorrect)
– Should be: ₹900 (10,000 × 9%)
Mistake 4: Missing Supplier/Customer GSTIN
Some freelancers skip GSTIN details, thinking it’s optional. It’s mandatory, even if one party is unregistered (mark it as “UNREGISTERED”).
Mistake 5: Sequential Number Gaps
GST invoices must have