A GST invoice is not just a bill. It is a legal document, and the rules for what it must contain come from CGST Rule 46. Get the fields right and your customer can claim input tax credit and your books stay clean. Get them wrong and you invite queries at filing time. This guide lists exactly what belongs on a GST invoice, shows a sample layout, and gives you a free way to make one without memorising any of it.
The mandatory fields on a GST invoice
Under CGST Rule 46, a tax invoice issued by a registered person must show all of the following.
- Supplier details, your business name, address and GSTIN.
- Invoice number, a unique serial for the financial year, up to 16 characters.
- Invoice date, the date the invoice is issued.
- Customer details, name and address, plus GSTIN if they are registered.
- Place of supply, the state, which decides CGST and SGST versus IGST.
- HSN or SAC code, for each item of goods or service.
- Description, quantity and unit for each line.
- Taxable value after any discount.
- GST rate and amount, split into CGST and SGST, or IGST.
- Whether tax is on reverse charge, if it applies.
- Total amount in figures, often also in words.
- Signature of the supplier or an authorised person, physical or digital.
A sample GST invoice layout
Here is how those fields come together on a simple invoice for a same-state sale at 18% GST.
| Item | HSN/SAC | Qty | Rate | Taxable | GST 18% |
|---|---|---|---|---|---|
| Consulting services | 998311 | 10 | 1,500.00 | 15,000.00 | 2,700.00 |
| Website design | 998314 | 1 | 25,000.00 | 25,000.00 | 4,500.00 |
Note how the 18% splits into CGST 9% and SGST 9% for a same-state sale. For a customer in another state, the same ₹7,200 would show as a single IGST 18% line instead.
How to make a GST invoice in five steps
- Add your business details and the customer's details, including GSTINs where they exist.
- Give the invoice a unique number for the financial year, and the date of supply.
- List each item with its HSN or SAC code, quantity, rate and taxable value.
- Apply the correct split. Same state is CGST and SGST. Different state is IGST.
- Show the grand total and add your signature.
Make a GST invoice free, without the manual work
You should not have to remember Rule 46 to send a bill. With Apna Invoice you pick the customer, add the items, and the GSTIN, place of supply, CGST, SGST and IGST split and HSN or SAC fields are handled for you. You get a clean, compliant PDF to share on WhatsApp in seconds. Create your first GST invoice free, or try the free GST calculator first.
Frequently asked questions
What fields are mandatory on a GST invoice?
Under CGST Rule 46 a tax invoice must show the supplier name, address and GSTIN, a unique invoice number and date, the customer details, HSN or SAC codes, the taxable value, the GST rate and amount split into CGST and SGST or IGST, the place of supply for inter-state sales, and the signature of the supplier.
Is HSN code mandatory on every invoice?
HSN for goods and SAC for services is required when either party is GST registered. The number of digits depends on turnover. For sales between two unregistered parties it is not strictly required, though it is good practice.
When do I charge CGST and SGST versus IGST?
When the supplier and the place of supply are in the same state, you charge CGST and SGST. When they are in different states, you charge IGST. The total tax is the same, only the split changes.
Can I make a GST invoice for free?
Yes. You can create a fully GST-compliant invoice free with Apna Invoice. The CGST, SGST and IGST split, HSN and SAC fields and a clean PDF are handled for you.