GST Tax Invoice Format: Every Mandatory Field Under Rule 46, Explained
A GST tax invoice is not just a bill. It is the document your customer uses to claim input tax credit, the document a GST officer asks for during an audit, and the document that has to match what you report in GSTR-1. If a mandatory field is missing, your buyer can lose credit and you can face a penalty, even when the tax itself was paid correctly.
Rule 46 of the CGST Rules, 2017 lists what a tax invoice must contain. This guide walks through each field in plain language, explains when the invoice must be issued, and covers the small details that most often go wrong.
Who must issue a tax invoice?
Every registered person who supplies taxable goods or services must issue a tax invoice under Section 31 of the CGST Act. There are two important exceptions:
- Composition taxpayers cannot charge GST, so they issue a bill of supply instead.
- Suppliers of exempt goods or services also issue a bill of supply for those exempt supplies.
If you are not registered under GST at all, you cannot issue a tax invoice and you must not show GST on your bills. A plain invoice or cash memo is what you issue.
The mandatory fields, one by one
Rule 46 lists the particulars below. Think of them as four groups: who is selling, who is buying, what is being sold, and how the tax is worked out.
1. Supplier details
- Name, address and GSTIN of the supplier. Use the legal or trade name exactly as it appears on your registration certificate. If you have several registrations (one per state), use the GSTIN of the state from which you are supplying.
2. Invoice number and date
- A consecutive serial number of not more than 16 characters, in one or more series, using letters, numbers, hyphen (-) or slash (/). It must be unique for the financial year. We cover this in detail in our invoice numbering guide.
- Date of issue.
3. Recipient details
- Registered recipient: name, address and GSTIN (or UIN). Get the GSTIN right. A wrong GSTIN means the invoice shows up in someone else's GSTR-2B and your customer cannot claim the credit.
- Unregistered recipient, invoice value 50,000 or more: name and address of the recipient, the address of delivery, and the name of the state with its state code.
- Unregistered recipient, value below 50,000: the name and address are not strictly required, but you must still record the state name and code if the recipient asks for it or for working out the place of supply. In practice, recording at least the state is good practice.
4. What was supplied
- HSN code for goods or SAC for services. The number of digits depends on your turnover. See how many HSN digits you need.
- Description of goods or services.
- Quantity (for goods) and the unit or Unique Quantity Code (UQC), such as NOS, KGS, MTR or BOX.
- Total value of the supply.
- Taxable value, after taking into account any discount or abatement.
5. Tax
- Rate of tax for each head: central tax, state or union territory tax, integrated tax, and cess where applicable.
- Amount of tax charged under each of those heads.
- Place of supply, with the name of the state, for inter-state supplies. This is what decides whether you charge CGST + SGST or IGST. Our guide on CGST, SGST and IGST explains how to work it out.
- Whether tax is payable on reverse charge. A simple "Reverse charge: Yes / No" line is the usual way to show it.
6. Delivery and signature
- Delivery address, if it is different from the place of supply.
- Signature or digital signature of the supplier or an authorised representative. Invoices sent electronically can be authenticated with a digital signature. Invoices generated under e-invoicing are treated as authenticated once the IRN is generated.
Optional but useful details
The law sets a minimum. Most well-run businesses add a few more things because they help them get paid:
- Payment terms and due date, for example "Payable within 30 days".
- Bank details or a UPI ID, so the customer does not have to ask.
- Total amount in words. Not a Rule 46 requirement, but almost every Indian business expects it. Our free amount in words converter uses the Indian lakh and crore system.
- Udyam registration number, if you are a micro or small enterprise. It reminds your buyer of the 45-day payment rule.
- PO number or reference number from the customer, which speeds up approval in larger companies.
When must the invoice be issued?
Timing matters because the date of the invoice usually decides the tax period in which you pay GST.
| Type of supply | Time limit |
|---|---|
| Goods involving movement | Before or at the time of removal of goods for supply |
| Goods not involving movement | Before or at the time of delivery or making available to the recipient |
| Services | Within 30 days of supply (45 days for banks, insurers and NBFCs) |
| Continuous supply of goods | Before or at the time each statement of account is issued or payment is received |
| Continuous supply of services | On or before the due date of payment as per the contract |
How many copies?
Rule 48 sets the number of copies:
- For goods: three copies. "Original for recipient", "Duplicate for transporter" and "Triplicate for supplier".
- For services: two copies. "Original for recipient" and "Duplicate for supplier".
If you are covered by e-invoicing, the transporter copy is not required because the invoice details are already on the government system. Our e-invoicing guide explains who is covered.
Common mistakes that cost buyers their credit
- Wrong GSTIN for the buyer. Always copy it from the buyer's registration or verify it on the GST portal. One wrong character sends the credit to someone else.
- Charging IGST on a local sale, or CGST + SGST on an inter-state sale. The buyer cannot simply move credit from one head to the other. You will have to issue a credit note and a fresh invoice.
- Missing place of supply on inter-state invoices.
- Re-using an invoice number after deleting a draft. Gaps are explainable; duplicates are not.
- Taxable value calculated before the discount. If the discount is shown on the invoice, tax is charged on the value after it.
- No HSN code, or a code with fewer digits than your turnover requires.
A simple checklist before you send
- Your name, address, GSTIN: correct state registration?
- Invoice number: next in series, 16 characters or less?
- Buyer GSTIN verified?
- Place of supply correct, and tax head (CGST + SGST or IGST) matches it?
- HSN or SAC on every line?
- Taxable value after discount, tax rate and tax amount on every line?
- Reverse charge Yes or No stated?
- Signed?
Create a compliant invoice in a few minutes
OwnInvoice's GST invoice editor, available with a free account, has fields for HSN/SAC codes on each line and works out CGST + SGST or IGST from your state and the customer's state. For a quick one-off invoice without signing up, the Invoice Studio runs in your browser, with GSTIN fields and custom fields you can use for place of supply and reverse charge. If the sale is exempt or you are under the composition scheme, use the bill of supply generator instead.
Note: This guide explains the general rules for information. GST law changes through notifications and circulars, so confirm anything specific to your business with a chartered accountant or GST practitioner.