GST invoice format: what's mandatory in 2026
A GST-compliant invoice isn't just a nicely formatted bill — it needs specific fields to be legally valid and to let your client claim input tax credit. Here's exactly what's required.
Mandatory fields on every GST invoice
- Invoice number and date — sequential, unique, and not repeated within a financial year.
- Your legal name, address, and GSTIN (GST registration number).
- Your client's name, address, and GSTIN (if they're GST-registered — required for B2B invoices).
- HSN or SAC code for each item or service — this classifies what you're billing for under GST.
- Description of goods or services.
- Quantity and unit (for goods) or the scope of service.
- Taxable value — the amount before GST.
- GST rate and amount, split into CGST + SGST (same state) or IGST (inter-state/export).
- Total invoice value, including tax.
- Place of supply — particularly important for inter-state transactions and export of services.
- Signature (physical or digital) of the supplier or an authorized representative.
A few fields freelancers often miss
The SAC (Services Accounting Code) is easy to skip if you're used to informal invoicing, but it's mandatory once you're GST-registered — it tells the tax authority exactly what category of service you provided. Most freelance/consulting services fall under a small set of common SAC codes; check the GST portal or your CA for the one that matches your work.
'Place of supply' also trips people up. For most services, it's where your client is located — this determines whether you charge CGST+SGST or IGST, and it directly affects the export-of-services treatment if your client is outside India.
Export of services
If you're invoicing a client outside India for services, this generally qualifies as an export of services and is typically zero-rated under GST — but specific conditions apply (payment received in foreign exchange, place of supply outside India, and a few others). You'll usually still issue an invoice with GST fields, marked appropriately as an export, even though the tax charged is nil.
Do you need to charge GST at all?
If your annual turnover is below the GST registration threshold (which varies by state and category of supply), you may not be required to register for GST at all — in which case you issue a regular invoice without GST fields rather than a GST invoice. Once you cross the threshold, or if you register voluntarily, GST invoicing becomes mandatory for every applicable transaction.