GST Invoice Tool

Every Indian freelancer, consultant, and small business owner registered under GST is legally required to issue a GST-compliant invoice for every taxable supply. But what exactly goes on a GST invoice? What format does it need to follow? And how do you create one without spending 30 minutes in Excel?

This guide covers everything you need to know about the GST invoice format in India for 2025 — mandatory fields, HSN/SAC codes, IGST vs CGST/SGST rules, and the fastest way to generate one.

What is a GST Invoice?

A GST invoice is a legal document issued by a GST-registered supplier to the buyer, showing the details of goods or services supplied, the applicable GST rate, and the total tax amount charged. It is the primary document for claiming Input Tax Credit (ITC), which makes it critical for both the buyer and the seller.

Without a proper GST invoice, your client cannot claim ITC — which means they'll push back on your billing or simply not pay on time.

Mandatory Fields in a GST Invoice (2025)

According to the CGST Rules, a valid GST invoice must contain the following fields:

Invoice number — a unique, consecutive serial number per financial year (e.g. INV-2025-001)
Invoice date — date of issue
Supplier name, address, and GSTIN
Recipient name, address, and GSTIN (if registered)
Place of supply — state where the supply is made
HSN code (for goods) or SAC code (for services)
Description of goods or services
Quantity and unit (for goods)
Total taxable value
Applicable GST rate — 5%, 12%, 18%, or 28%
CGST + SGST amount (intra-state) or IGST amount (inter-state)
Total invoice value (taxable value + GST)
Signature or digital signature of the supplier

Missing even one of these fields can make your invoice non-compliant and block your client from claiming ITC.

IGST vs CGST + SGST — Which Applies to You?

This is where most freelancers get confused. The rule is simple:

Intra-state supply (you and your client are in the same state) → charge CGST + SGST (split equally, e.g. 9% + 9% for 18% GST)
Inter-state supply (you and your client are in different states) → charge IGST (e.g. 18% IGST)

Example: A designer in Mumbai billing a client in Mumbai charges 9% CGST + 9% SGST. The same designer billing a client in Delhi charges 18% IGST.

The total tax amount is the same — only the split changes.

HSN and SAC Codes for Common Freelance Services

If you're a service provider, you'll use SAC (Service Accounting Code) codes. Here are the most common ones:

Service	SAC Code	GST Rate
Software development	998314	18%
Graphic design	998383	18%
Content writing	998390	18%
Photography	998382	18%
Consulting / management	998311	18%
Digital marketing	998361	18%
Video production	998392	18%
Architecture services	998311	18%

Most freelance services fall under 18% GST. When in doubt, check the GST Council's official SAC code list or consult your CA.

GST Invoice Format — Step by Step

Here's how to structure a correct GST invoice:

Header section:

Your business name + logo
"TAX INVOICE" label (mandatory wording)
Your GSTIN
Your address

Invoice details:

Invoice number (sequential per FY)
Invoice date
Due date (optional but recommended)

Bill To section:

Client name and address
Client GSTIN (if registered)
Place of supply (state)

Line items table:

Description of service
SAC code
Quantity / hours
Rate
Taxable amount

Tax summary:

Taxable value subtotal
CGST @ 9% + SGST @ 9% (or IGST @ 18%)
Total invoice value in INR

Bank details:

Account name, number, IFSC, bank name

Signature:

Your signature or stamp

Invoice Number Format Rules

The GST law doesn't prescribe a specific format for invoice numbers, but they must be:

Unique — no two invoices in a financial year can have the same number
Sequential — must follow a logical order
Alphanumeric — letters and numbers are both allowed, maximum 16 characters

Common formats used by freelancers:

INV-2025-001, INV-2025-002
YOURINITIALS/2025-26/001
2025-26/001

Reset your invoice number series at the start of every financial year (April 1).

Time Limit to Issue a GST Invoice

For services, you must issue the GST invoice within 30 days of the date of supply. Missing this deadline can attract penalties under GST law.

For most freelancers, best practice is to raise the invoice on the day the work is delivered or the month ends for retainer clients.

The Fastest Way to Create a GST Invoice

Manually creating a GST invoice in Excel or Word every time is error-prone and time-consuming. A single wrong HSN code or missing field can make your invoice non-compliant.

Invoqo is a free GST invoice generator built specifically for Indian freelancers and small businesses. It handles:

Automatic IGST vs CGST/SGST calculation based on your and your client's state
SAC code lookup
Sequential invoice numbering
Instant PDF download

No signup required. Generate your first GST invoice in under 2 minutes at invoqo.in/invoice.

Frequently Asked Questions

Do I need to issue a GST invoice if my client is not GST registered? Yes. If you are GST registered, you must issue a GST invoice for every taxable supply, regardless of whether your client is registered. You can still charge GST — your client just won't be able to claim ITC.

What is the threshold for GST registration in India? For service providers, the threshold is ₹20 lakh annual turnover (₹10 lakh for special category states). Once you cross this, registration is mandatory.

Can I issue a GST invoice for advance payments? Yes — this is called a Receipt Voucher. If you receive an advance before delivering the service, you must issue a receipt voucher showing the GST amount.

Is a digital signature mandatory on a GST invoice? No. A manual signature or even a digital facsimile signature is acceptable. Digital signatures using DSC are optional for most freelancers.

What happens if I issue a wrong GST invoice? You can issue a Credit Note or Debit Note to correct a previously issued invoice. You cannot simply delete or re-issue the same invoice number.