A GST invoice is valid only if it carries a fixed set of fields. If one is missing, your buyer may be unable to claim input tax credit, and the bill can be questioned in an audit.
Here is exactly what a tax invoice must show under the GST rules.
The fields every GST invoice must have
- Your name, address and GSTIN.
- A unique invoice number. Consecutive, not repeated within the financial year.
- The date of issue.
- Buyer's name, address and GSTIN if they are registered.
- Place of supply and the state code, especially for inter-state sales.
- HSN code for goods, or SAC code for services.
- Description, quantity and unit of the goods or services.
- Taxable value after any discount.
- Tax rate and amount, split into CGST + SGST, or IGST.
- Whether reverse charge applies.
- Signature of the supplier or an authorised person.
CGST + SGST, or IGST?
This depends on where the buyer is. Same state as you means it is intra-state: you charge CGST and SGST, each at half the total rate. A different state means inter-state: you charge one IGST at the full rate. The place of supply decides it, not where you are sitting.
How many HSN digits
The number of HSN digits scales with turnover. Up to ₹5 crore, 4 digits are enough for B2B invoices; above ₹5 crore, use 6. Services use the SAC code instead.
When a tax invoice isn't needed
If you are under the composition scheme, or selling exempt goods, you issue a bill of supply instead — it has no tax breakup. For sales below ₹200 to an unregistered buyer, a consolidated invoice at day's end is allowed.