GST invoice format: what every tax invoice must show
A GST tax invoice needs about 15 specific details. Miss one and your client may not be able to claim input tax credit. Here is the full list, in plain language.
Mandatory fields on a GST tax invoice
These come from Rule 46 of the CGST Rules, 2017.
| Field | What to write |
|---|---|
| Supplier details | Your name, address and GSTIN |
| Invoice number | A unique, consecutive number for the financial year, up to 16 characters (for example INV/26-27/001) |
| Invoice date | The date of issue |
| Recipient details | Name, address and GSTIN if the buyer is registered |
| Unregistered buyer, value above ₹50,000 | Name, address and place of supply with state name and code |
| HSN or SAC code | The code for each good (HSN) or service (SAC) |
| Description | What was supplied |
| Quantity and unit | For goods |
| Value | Total value and taxable value, after any discount |
| Tax rate and amount | CGST and SGST, or IGST, shown separately |
| Place of supply | State name, required for inter-state supplies |
| Signature | Signature or digital signature of the supplier or authorised person |
CGST + SGST or IGST: which one applies?
Compare your state with the place of supply. If they are the same state, the GST rate splits in half between CGST and SGST (18% becomes 9% + 9%). If they are different states, the full rate is charged as IGST. The first two digits of a GSTIN are the state code, which is how BillKaro detects this for you.
Not registered under GST?
If your turnover is below the registration limit and you are not registered, you cannot charge GST. You issue a bill of supply instead of a tax invoice. BillKaro switches to a bill of supply when you tick "I'm not GST registered".
Common mistakes
Restarting invoice numbers mid-year, writing the wrong state code, charging IGST on a same-state sale, and leaving out the HSN/SAC code are the errors that most often cause input tax credit problems for buyers.
Last updated 2026-10-03. This page is general information, not tax advice. Confirm specific cases with a chartered accountant.