GST invoice format explained
A GST invoice must carry both parties' GSTINs, a consecutive invoice number and date, an HSN or SAC code per line, the taxable value after discount, and the tax shown by component — CGST and SGST for intra-state supply, or IGST for inter-state supply. The total is conventionally rounded to the nearest rupee and repeated in words.
Required fields
- Supplier name, address and GSTIN.
- A consecutive invoice number, unique within the financial year, and the date of issue.
- Recipient name, address and GSTIN where they are registered.
- HSN code for goods, or SAC code for services, per line item.
- Description, quantity and unit for each line.
- Taxable value after any discount.
- Rate and amount of tax, shown per component.
- Place of supply, and the delivery address where it differs.
- Whether tax is payable on reverse charge.
- Signature or digital signature of the supplier.
CGST + SGST or IGST?
This is determined by the place of supply, not by where your customer's head office is. If the supply is within the same state as the supplier, the combined rate splits into CGST and SGST at half each — an 18% supply becomes 9% CGST plus 9% SGST. If the supply crosses state lines, a single IGST at the full 18% applies instead.
| Supply | Tax charged | Example at 18% |
|---|---|---|
| Within the same state | CGST + SGST | 9% + 9% |
| Between states | IGST | 18% |
| Export / SEZ | Usually zero-rated | 0% (conditions apply) |
HSN and SAC codes
HSN codes classify goods and SAC codes classify services. The number of digits you must quote depends on your turnover — smaller businesses quote fewer digits. Use the code that matches what you actually supplied rather than a generic one; the code drives the rate.
Rounding and amount in words
GST invoices conventionally round the final payable amount to the nearest rupee, showing the rounding adjustment as its own line so the arithmetic remains transparent. The total is then repeated in words beneath the totals block. Both are enabled by default on our GST generator.
Frequently asked questions
When do I charge IGST instead of CGST and SGST?
When the place of supply is in a different state from the supplier. Intra-state supply is split into CGST and SGST; inter-state supply is charged as a single IGST at the full rate.
Is HSN mandatory on a GST invoice?
Yes for most registered suppliers, though the number of digits required depends on turnover. Services use SAC codes instead.