The GST invoice format, explained

What Indian GST rules require on a tax invoice, in plain language.

Mandatory fields

• Supplier details: your legal name, address, and GSTIN.
• Invoice number: unique, consecutive, within the financial year.
• Invoice date and, for services, the date of supply if different.
• Recipient details: name, address, and GSTIN for registered buyers (B2B). For B2B supplies this is what lets your client claim input tax credit.
• Place of supply with state code — this determines which tax applies.
• HSN or SAC codes: HSN for goods, SAC for services, per line item.
• Taxable value, rate, and tax amount per line or in a summary.

CGST + SGST or IGST?

It depends on the place of supply:

• Intrastate (same state): the GST splits into equal halves — CGST (central) and SGST (state). An 18% rate shows as CGST 9% + SGST 9%.
• Interstate (different states, or exports): the full rate is charged as IGST instead.

e-Invoicing and the QR code

Businesses above the notified turnover threshold must register invoices with the government Invoice Registration Portal (IRP), which returns an IRN (Invoice Reference Number) and a signed QR code that must appear on the invoice. Below the threshold, a standard GST-compliant invoice is sufficient.

Common mistakes

• Reusing or skipping invoice numbers after deleting an invoice — cancel, never delete.
• Showing a single "GST" line for intrastate supplies instead of the CGST/SGST split.
• Missing HSN/SAC codes, which are mandatory above modest turnover thresholds.
• Forgetting the buyer's GSTIN on B2B invoices, blocking their input credit.

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