How to Write a GST Invoice in India (Step-by-Step Guide)

Under India's GST law, a "tax invoice" isn't just any bill — it's a document with a defined set of mandatory fields. Get one wrong or leave one out, and your buyer may not be able to claim input tax credit on it. Here's what a compliant GST invoice actually needs, in the order it usually appears on the page.

1. Supplier and buyer details

Your legal business name, address, and GSTIN (15-digit GST identification number) at the top. Below it, the buyer's name, address, and GSTIN if they're also registered — this is what lets them claim credit.

2. Invoice number and date

A unique, sequential invoice number (no gaps, no repeats within a financial year) and the date of issue. Most businesses prefix it by financial year, e.g. INV/2026-27/0142.

3. HSN or SAC code

Every line item needs an HSN code (goods) or SAC code (services). These determine the applicable GST rate and are checked during any audit.

4. Taxable value and GST breakup

The taxable value of each item, then GST split correctly:

• CGST + SGST — for sales within the same state
• IGST — for sales across state lines

Lumping tax into one unlabelled "GST" line is a common mistake that gets invoices rejected during reconciliation.

5. Place of supply

Required for any inter-state sale, since it determines whether CGST/SGST or IGST applies.

6. Signature

A physical or digital signature from an authorised signatory. E-invoices generated through the GST portal have this handled automatically via the IRN/QR code.

The fastest way to get all of this right

Typing this out correctly by hand every time is exactly where mistakes creep in — a missing HSN code, a state mismatch, a skipped invoice number. Our GST Invoice Generator pre-fills your GSTIN and business details once, then handles the CGST/SGST/IGST split automatically based on the buyer's state, so you can't accidentally skip a required field.

Not GST-registered, or billing a client who doesn't need GST fields? A plain Invoice Generator covers that case without the extra compliance fields.