GST invoice requirements: a field-by-field checklist for India

Short answer: a GST tax invoice must show the supplier's name, address and GSTIN, a unique sequential invoice number and date, the recipient's details, a description of goods or services with HSN or SAC code, quantity, taxable value, tax rate and amount split into CGST and SGST or IGST, the place of supply, and a signature. Rule 46 of the CGST Rules lists the fields.

This is a practical checklist, not legal or tax advice. Rules and thresholds change by notification. Confirm with the GST portal or your chartered accountant.

What fields does a tax invoice need?

• Supplier: name, address and GSTIN.
• Invoice number: consecutive serial number, unique for the financial year, up to 16 characters, using letters, numbers and the characters hyphen and slash.
• Invoice date.
• Recipient: name and address. GSTIN if registered. For unregistered recipients above specified values, name, address and state with code are needed.
• HSN code for goods or SAC for services. The number of digits required depends on your turnover, so check the current notification.
• Description of goods or services, quantity and unit.
• Total value, any discount, and the taxable value after discount.
• Tax rate and amount: CGST, SGST or UTGST, IGST and cess, shown separately.
• Place of supply with the state name and code when the supply is inter-state.
• Delivery address if different from the billing address.
• Whether tax is payable on reverse charge.
• Signature or digital signature of the supplier or authorised person.

How do CGST, SGST and IGST work?

• If the supplier and the place of supply are in the same state, tax is split: half CGST and half SGST (or UTGST in a union territory). An 18 percent rate becomes 9 plus 9.
• If they are in different states, the full rate is IGST: 18 percent as IGST.
• The place of supply rules decide which applies, and for services they are not always the buyer's address. Be careful.

Worked example for 1,000 rupees taxable value at 18 percent, intra-state: CGST 90, SGST 90, total 1,180. Inter-state: IGST 180, total 1,180.

How should invoice numbers be managed?

• No gaps and no duplicates within the series for a financial year. If you issue from several branches, use a series per branch with a prefix.
• Do not reuse a number for a cancelled invoice. Keep it, mark it cancelled, and issue a new one.
• Credit notes and debit notes have their own series.
• Allocate the number at the moment of finalising, inside the same database transaction that saves the invoice, so concurrent users never get the same number.

When do you issue a bill of supply instead?

A bill of supply is used instead of a tax invoice when you supply exempt goods or services, or if you are a composition scheme dealer, who may not collect tax from customers. It has similar fields minus the tax breakdown. A composition dealer's invoice must also state that it is a composition taxable person.

What about invoices to consumers?

For B2C sales many retailers use a simplified bill with the required fields, with prices often inclusive of tax. The calculation of the tax portion from an MRP that includes GST must be right and consistent. I explain the method, including rounding, in GST-inclusive MRP POS calculation.

What about e-invoicing?

Businesses above the notified turnover threshold must report B2B invoices to the Invoice Registration Portal, which returns an Invoice Reference Number (IRN) and a signed QR code that must appear on the invoice. Software that supports it builds the JSON, submits it and prints the QR. If you are near the threshold, choose software that already does this.

Common errors

• Wrong place of supply, giving CGST and SGST where IGST applies.
• Missing or wrong HSN.
• Rounding applied per line in one place and per invoice in another, so totals disagree with returns.
• Editing a finalised invoice instead of issuing a credit note.
• Skipped numbers because drafts consumed numbers.
• Customer GSTIN typed wrongly. Validate its format and checksum in software.

Software that enforces these rules is easier than discipline. See the billing software buyer's guide, and how Rechvix and NodeDR POS handle them.