What a GST invoice must contain
The fields a GST tax invoice needs, when the tax splits into CGST and SGST versus IGST, and the mistakes that make an invoice unusable for your buyer.
6 min read · updated
A GST invoice is not just a bill with tax added. Your buyer uses it to claim input tax credit, so a missing field is their problem before it is yours, and they will ask for a corrected copy. Getting it right the first time is mostly a matter of knowing which fields are not optional.
The fields that are not optional
- Your name, address and GSTIN.
- A sequential invoice number, unique within the financial year. Gaps and duplicates both cause questions.
- The date of issue.
- The buyer name, address and GSTIN if they are registered.
- Place of supply, which decides whether the tax splits or not.
- HSN code for goods, or SAC for services.
- Description, quantity and unit for each line.
- Taxable value per line, after any discount.
- The rate and amount of tax, shown separately rather than folded into the total.
- A signature or digital signature.
CGST and SGST, or IGST
This is the part most people get wrong, and it turns on place of supply rather than on where you are. If the supply is within your state, the tax splits in half: an 18% rate becomes 9% CGST and 9% SGST. If it crosses a state line, the whole 18% is IGST instead. The buyer pays the same amount either way, so the error is invisible on the total and shows up only when someone reconciles a return.
| Supply | Rate | How it appears |
|---|---|---|
| Within state | 18% | CGST 9% + SGST 9% |
| Across states | 18% | IGST 18% |
| Within state | 12% | CGST 6% + SGST 6% |
| Across states | 12% | IGST 12% |
On a 2,40,000 taxable value at 18%, an inter-state supply carries 43,200 of IGST. The same sale within your state carries 21,600 CGST and 21,600 SGST. Same 2,83,200 invoice, different returns.
Generate a compliant GST invoiceGST-compliant tax invoices with CGST, SGST and IGST breakdowns.Four mistakes worth avoiding
Folding tax into the line price
A line that reads "Consulting, 59,000" with no tax breakdown is not a tax invoice. The taxable value and the tax have to be separable, because your buyer claims credit on the tax alone.
Guessing the HSN code
The code drives the rate, so a wrong code usually means a wrong rate. Look it up rather than reusing whatever was on the last invoice for a different product.
Look up an HSN or SAC codeSearch HSN codes and their GST rates by keyword.Not checking the buyer GSTIN
A transposed character in a GSTIN is easy to make and hard to spot. Validating the format and check digit catches typos immediately, though it will not tell you whether the registration is active, which needs the GST portal.
Validate a GSTINCheck the format and checksum of a GST number.Editing an issued invoice
Once an invoice is out, corrections belong in a credit or debit note, not in a quiet edit. The original stays as it was and the adjustment is documented separately, which is what leaves an audit trail rather than a mystery.