GST invoice format: what a valid tax invoice must contain

Updated: 23 August 2026 · Reviewed for the current GST 2.0 rate structure and portal behaviour.

A tax invoice isn't a design question — it's a compliance document whose contents are prescribed by the GST invoice rules. Here is what must be on it, when a bill of supply is used instead, and how credit and debit notes work.

Mandatory particulars of a tax invoice

• Supplier's name, address and GSTIN
• A consecutive serial number, unique for the financial year (letters, numerals, "-" and "/" allowed)
• Date of issue
• Buyer's name and address; buyer's GSTIN if registered
• Place of supply with state name/code (essential for the CGST/SGST vs IGST decision)
• HSN/SAC code for each line (digit-length depends on turnover)
• Description, quantity and unit, total value
• Taxable value after discounts
• Rate and amount of tax — CGST, SGST/UTGST, IGST and cess shown separately
• Whether tax is payable on reverse charge
• Signature or digital signature of the supplier or authorised representative

Tax invoice vs bill of supply

Credit notes and debit notes

A credit note reduces what the buyer owes (sales return, rate charged too high, deficient supply); a debit note increases it (rate charged too low, quantity under-billed). Both must reference the original invoice and appear in the CDNR/CDNUR tables of your GSTR-1. A credit note's tax reduction must be reported by the deadline the law sets for the year — after that, the tax reduction lapses even if the commercial adjustment happens.

Common invoice mistakes that cost money

• Wrong place of supply → wrong tax head → the buyer's credit is at risk and the correction is painful.
• Duplicate or broken number series → questions in Table 13 of GSTR-1.
• Missing HSN at the required digit length → portal-side validation failures.
• Charging tax on a bill of supply, or issuing a tax invoice while under composition.