How to Make a GST Invoice: Format, Rules and Example
What every GST invoice must include, when to charge CGST + SGST or IGST, and a step-by-step way to make one correctly.
Gaddibook Team · · 4 min read
Every business registered under GST must issue a proper tax invoice for each taxable sale. A missing or wrong detail can cost your buyer their input tax credit, and that problem usually comes back to you. This guide shows what a GST invoice must include and how to make one correctly.
Who needs to issue a GST invoice?
If you are registered under GST as a regular taxpayer, you must issue a tax invoice for every taxable sale.
- Composition dealers issue a bill of supply instead and cannot charge GST on it.
- For exempt or nil-rated items, you also issue a bill of supply.
- For small B2C sales below ₹200, you can issue one consolidated invoice at the end of the day, as long as the buyer does not ask for an invoice.
What a GST invoice must include
Rule 46 of the CGST Rules lists the details a tax invoice must carry:
| Field | What to write |
|---|---|
| Your details | Business name, address and GSTIN |
| Invoice number | A unique, consecutive number (up to 16 characters) for the financial year |
| Invoice date | The date the invoice is issued |
| Buyer details | Name, address and GSTIN (if the buyer is registered) |
| Place of supply | State name and state code |
| HSN or SAC code | For each item or service |
| Description, quantity and unit | For example: Sunflower oil 1 L, 10 PCS |
| Taxable value | Value after any discount |
| Tax rate and amount | CGST + SGST, or IGST, shown separately |
| Invoice total | In figures and in words |
| Reverse charge | Whether tax is payable on reverse charge |
| Signature | Your signature or digital signature, or that of an authorised person |
For a sale to an unregistered buyer worth ₹50,000 or more, also add the buyer's name and address, and the delivery address with state name and code.
CGST + SGST or IGST?
The tax you charge depends on where the supply goes:
- Same state (intra-state): split the tax equally into CGST and SGST. An 18% item becomes 9% CGST + 9% SGST.
- Different state (inter-state): charge the full rate as IGST.
How to make a GST invoice, step by step
- Choose the right document: tax invoice, bill of supply, or a credit note for returns.
- Use the next number in your invoice series. Do not skip or reuse numbers within a financial year.
- Enter the buyer's name and address, and their GSTIN for B2B sales. For a new customer, verify the GSTIN on the GST portal.
- Add each item with its HSN code, quantity, unit and rate.
- Apply any discount before tax, so the taxable value is correct.
- Calculate tax: CGST + SGST for sales within your state, IGST for other states.
- Check the total, write the amount in words, and sign.
- Give the original copy to the buyer and keep your copy.
Worked example
A shop in Kolkata sells 10 units at ₹500 each to a registered buyer in Kolkata. The item is taxed at 18%.
| Line | Amount |
|---|---|
| Taxable value (10 × ₹500) | ₹5,000 |
| CGST @ 9% | ₹450 |
| SGST @ 9% | ₹450 |
| Invoice total | ₹5,900 |
If the same buyer were in Bihar, the invoice would show IGST @ 18% = ₹900 instead, and the total would still be ₹5,900.
GST rates changed for many items from 22 September 2025, so confirm the current rate for each product when you set up your item list.
How many copies do you need?
- Goods: three copies. The original goes to the buyer, the duplicate to the transporter, and you keep the triplicate.
- Services: two copies. The original goes to the buyer and you keep the duplicate.
Do you need e-invoicing?
If your aggregate annual turnover has crossed ₹5 crore in any financial year since 2017-18, your B2B invoices must be reported on the Invoice Registration Portal (IRP) and must carry an IRN and QR code. Smaller businesses can keep issuing normal invoices.
Common mistakes to avoid
- Wrong or missing buyer GSTIN on a B2B invoice, so the buyer cannot claim input tax credit
- Missing HSN codes. See our guide on HSN codes on GST invoices.
- Gaps or repeats in the invoice number series
- Charging CGST + SGST on an inter-state sale
- Calculating tax on the price before discount
Make GST invoices faster with Gaddibook
Gaddibook keeps your business details, item list and HSN codes ready, so each invoice takes seconds instead of minutes. Your invoices also feed the GST reports you need at filing time. See POS billing in Gaddibook, read how to file GSTR-1, or view pricing.