What Is a GST Invoice and Why Does It Matter?
If you're a freelancer or small business owner in India registered under the Goods and Services Tax (GST) regime, you're legally required to issue GST-compliant invoices for every taxable supply. A valid GST invoice must include specific fields — your GSTIN, HSN/SAC code, tax breakup (CGST, SGST or IGST), and more. Getting any of these wrong can delay input tax credit (ITC) claims for your clients and attract scrutiny from the GST department.
This guide walks you through what a proper GST invoice must contain, common mistakes to avoid, and how InvoiceAI's free GST invoice generator lets you create compliant invoices in under three minutes.
Mandatory Fields on a GST Invoice
Under GST rules, a tax invoice must include the following:
- Supplier GSTIN — your 15-digit GST identification number
- Invoice number and date — unique sequential number for each financial year
- Recipient details — name, address, and GSTIN (for B2B supplies)
- HSN / SAC code — Harmonised System of Nomenclature for goods, or Service Accounting Code for services
- Taxable value and tax rate — value before tax + applicable CGST/SGST (intra-state) or IGST (inter-state) rates
- Total invoice value — sum of taxable value + GST
- Place of supply — state code to determine whether CGST+SGST or IGST applies
- Digital or physical signature
CGST vs SGST vs IGST — Which Applies to You?
The type of GST you charge depends on whether the transaction is intra-state or inter-state:
- Intra-state supply (supplier and buyer in same state): Charge CGST + SGST, each at half the applicable rate. E.g., for 18% GST — 9% CGST + 9% SGST.
- Inter-state supply (supplier and buyer in different states): Charge IGST at the full rate. E.g., 18% IGST.
InvoiceAI automatically picks the correct tax type based on the supplier's and client's state — you never have to calculate it manually.
Common GST Invoice Mistakes That Cost Freelancers
- Wrong HSN/SAC code — Using an incorrect code means your invoice won't match GST return data and your client can't claim ITC.
- Missing place of supply — Required for all B2B invoices. Skipping it makes the invoice non-compliant.
- Sequential numbering errors — GST invoices must be numbered sequentially within each financial year. Gaps or duplicates trigger notices.
- Charging wrong tax type — Billing CGST+SGST on an inter-state transaction (or vice versa) creates a mismatch in GSTR-1 filing.
- No digital signature on e-invoices — Mandatory for businesses above the e-invoicing turnover threshold (₹5 crore as of 2024).
How InvoiceAI's Free GST Invoice Generator Works
InvoiceAI removes the complexity of GST invoicing with a guided, automated workflow:
Step 1 — Set Up Your Company Profile
Add your GSTIN, business name, address, and state once. InvoiceAI stores this and pre-fills it on every invoice. Upload your logo for a professional look.
Step 2 — Add Your Client
Enter the client's GSTIN and state. InvoiceAI automatically detects whether to apply CGST+SGST or IGST based on the supply location.
Step 3 — Add Line Items with HSN/SAC Codes
Type your service or product description. InvoiceAI suggests HSN/SAC codes based on your category. Select the applicable GST rate (5%, 12%, 18%, or 28%) per line item.
Step 4 — Review the Tax Breakdown
InvoiceAI shows a live tax summary — taxable value, CGST, SGST or IGST, and total invoice amount — before you send.
Step 5 — Send and Get Paid
Share the invoice via email or WhatsApp with a built-in UPI payment link. Clients can pay directly from the invoice without needing a separate payment gateway.
GST Invoice vs Bill of Supply: What's the Difference?
If you're registered under the GST Composition Scheme or supply exempt goods/services, you must issue a Bill of Supply instead of a tax invoice — you cannot charge or collect GST from your customer in these cases. InvoiceAI supports both formats.
Who Needs a GST Invoice?
- Freelancers with annual turnover above ₹20 lakh (₹10 lakh for special category states)
- Small businesses registered under regular GST scheme
- Consultants, designers, developers, and service providers billing GST-registered clients
- E-commerce sellers on Amazon, Flipkart, or Meesho
Even if you are below the turnover threshold and not registered, many corporate clients require a GST invoice for ITC claims — so having a professional invoicing tool matters regardless.
Free GST Invoice Template (PDF Download)
InvoiceAI generates print-ready, professionally designed GST invoice PDFs that include all mandatory fields. You can customise the template colour, add your logo, and set a default payment terms message. No design skills needed.
Frequently Asked Questions
Is InvoiceAI's GST invoice generator really free?
Yes. The free plan lets you create 5 GST invoices per month with no credit card required. Premium plans unlock unlimited invoices, recurring billing, and AI-assisted invoice drafting.
Can I create invoices in INR with UPI payment links?
Yes. InvoiceAI supports INR as the default currency and lets you attach a UPI ID or QR code to each invoice so clients can pay instantly via PhonePe, Google Pay, or Paytm.
Does InvoiceAI support e-invoicing (IRP portal)?
Direct IRP portal integration is on the roadmap. Currently, InvoiceAI generates fully compliant tax invoices that can be manually uploaded to the IRP for businesses above the e-invoicing threshold.
Can I download the invoice as a PDF?
Yes — one click generates a professional PDF. You can email it directly from InvoiceAI or download it to send via WhatsApp.