Every GST-registered shop in India has to issue a proper tax invoice, and the GST invoice format is not a matter of taste. Rule 46 of the CGST Rules, 2017 lists exactly what a tax invoice must show. Miss a field and the bill is still a bill, but your business customer may lose the input tax credit (ITC) on it, and that customer will come back to you to fix it. This guide walks through how to make a GST bill correctly, field by field, with a worked example you can check with a calculator.
What Is a GST Tax Invoice?
A tax invoice is the document a registered supplier issues when it sells taxable goods or services. It records what was sold, its value, the GST charged, and who sold it to whom. For a B2B sale it is also the buyer's proof for claiming ITC, which is why the format matters so much more than on a simple cash memo.
Not every document is a tax invoice. A composition dealer, or a shop selling only exempt goods, issues a Bill of Supply instead, with no tax shown. We cover that case in our guide to the composition scheme and Bill of Supply.
Mandatory Fields in a GST Invoice (Rule 46)
These are the fields Rule 46 asks for. Your billing software should fill most of them automatically from your company and item settings.
- Your name, address and GSTIN as registered on the GST portal.
- Invoice number: consecutive, unique for the financial year, at most 16 characters, using only letters, digits, hyphen (-) and slash (/).
- Date of issue.
- Buyer's name, address and GSTIN if the buyer is registered.
- For an unregistered buyer, when the invoice value is ₹50,000 or more: name, address, delivery address and the state name and code.
- HSN code for goods or SAC for services. Businesses with turnover up to ₹5 crore must show at least 4 digits on B2B invoices; above ₹5 crore, 6 digits on all invoices.
- Description, quantity and unit of each item.
- Total value and taxable value after any discount.
- Rate and amount of tax: CGST and SGST (or UTGST) for a sale within your state, IGST for a sale to another state.
- Place of supply with the state name, for inter-state sales.
- Delivery address if it differs from the place of supply.
- Whether tax is payable on reverse charge.
- Signature or digital signature of you or your authorised person.
The document should be titled "Tax Invoice". If you also sell exempt items on the same bill, Rule 46A allows a single "Invoice-cum-Bill of Supply".
GST Bill Format Example: Within the State and Outside
Say a shop in Tamil Nadu sells to a registered retailer in Coimbatore (same state). The bill has two lines, priced before tax:
| Item | HSN | Qty | Rate | Taxable value | GST rate | CGST | SGST |
|---|---|---|---|---|---|---|---|
| Biscuits (pack) | 1905 | 20 | ₹50.00 | ₹1,000.00 | 5% | ₹25.00 | ₹25.00 |
| Electric kettle | 8516 | 1 | ₹1,500.00 | ₹1,500.00 | 18% | ₹135.00 | ₹135.00 |
| Total | ₹2,500.00 | ₹160.00 | ₹160.00 |
Total tax is ₹320, so the invoice total is ₹2,820. If the same buyer were in Karnataka, the sale would be inter-state: no CGST or SGST, but IGST of ₹50 (5% of ₹1,000) plus ₹270 (18% of ₹1,500), the same ₹320 in total, and the invoice must state Karnataka as the place of supply.
What if your prices include GST?
Most shops display a tax-inclusive price. The invoice still has to show the taxable value and the tax separately. Work backwards: a ₹105 item at 5% has a taxable value of ₹100 (105 ÷ 1.05) and tax of ₹5. Good billing software does this split for every line, so the printed bill shows both numbers even though the customer only saw ₹105 on the shelf.
B2B vs B2C Invoices: What Changes
- B2B (registered buyer): the buyer's GSTIN is compulsory, and the HSN code must be shown. These bills go line by line into GSTR-1, and the buyer claims ITC on them.
- B2C (consumer): no GSTIN. Below ₹50,000 the buyer's name and address are optional. These sales are reported in GSTR-1 as a state-wise and rate-wise summary.
- Small B2C sales: for sales under ₹200 where the customer does not ask for an invoice, the rules let you issue one consolidated invoice for the day.
Our step-by-step guide to filing GSTR-1 for a retail shop shows how each type of bill is reported.
Invoice Numbering Rules
The number must be unique within a financial year (April to March) and follow a series. Prefixes like INV/2026-27/0001 are fine as long as the whole number stays within 16 characters. You can run separate series for different branches or document types, but never reuse a number in the same year and never leave silent gaps. A cancelled bill should stay in the series marked as cancelled, not be deleted.
When Do You Have to Issue the Invoice?
- Goods: at or before the time the goods are removed or delivered.
- Services: within 30 days of supplying the service.
- Copies: for goods, the original goes to the buyer, the duplicate to the transporter and the triplicate stays with you. For services, an original and a duplicate.
Common GST Invoice Mistakes
- Wrong buyer GSTIN, which sends the ITC to the wrong business or to nobody
- CGST and SGST charged on an inter-state sale, where IGST was due
- Outdated rates: many items moved slab on 22 September 2025, so check the new GST rates list
- Tax worked out on the rounded line total instead of the taxable value
- Handwritten bills with no HSN code on B2B sales
How to Make a GST Bill in Billing Software
Writing all of this by hand on every bill is slow and error-prone. In Billux you set your GSTIN, address and state once, and each item carries its HSN code and GST rate. When you type an HSN code, Billux suggests the GST rate from a table checked against the September 2025 rate notifications. Then a bill takes seconds:
- Pick or scan the items. Quantity, rate, taxable value and tax fill in.
- Pick the customer. For a registered buyer, the GSTIN prints on the bill. If the buyer's state differs from yours, Billux charges IGST instead of CGST and SGST.
- Save and print on A4 or a 58/80 mm thermal printer, or send the bill on WhatsApp.
Invoice numbers run per financial year automatically, and every bill feeds the GSTR-1 and GSTR-3B reports. It works the same on the retail counter, the supermarket and pharmacy tills, and the full invoice screen. Plans start at ₹2,500 a year. See pricing, or read our wider GST billing guide.
The Bottom Line
A correct GST invoice format is a short checklist: your details, a clean number and date, the buyer's details, HSN, taxable value, the right tax split and a signature. Get the setup right once in your billing software and every bill after that comes out compliant.
Frequently Asked Questions
What are the mandatory fields in a GST invoice?
Rule 46 requires the supplier's name, address and GSTIN; a unique consecutive invoice number of up to 16 characters; the date; the buyer's name, address and GSTIN if registered; HSN or SAC codes; description, quantity and unit; taxable value; GST rate and amount split into CGST/SGST or IGST; place of supply for inter-state sales; whether reverse charge applies; and a signature.
Is HSN code mandatory on a GST bill?
Yes for most businesses. With turnover up to ₹5 crore, a 4-digit HSN code is mandatory on B2B invoices. Above ₹5 crore, a 6-digit HSN code is required on all invoices.
Can I make a GST bill without the customer's GSTIN?
Yes. A sale to an unregistered customer is a B2C sale and does not need a GSTIN. If the invoice value is ₹50,000 or more, you must still record the customer's name, address and state.
How many characters can a GST invoice number have?
Up to 16 characters, using letters, digits, hyphens and slashes. The number must be unique within the financial year.
What is the difference between a tax invoice and a bill of supply?
A tax invoice shows the GST charged and lets a registered buyer claim input tax credit. A bill of supply shows no tax and is issued by composition dealers or for exempt goods.
