GST Invoice Rules: What a Valid Tax Invoice Must Show

Why the invoice is so important

Under GST, the tax invoice is the legal backbone of a transaction. It’s the document on which your buyer claims input tax credit, on which returns are built, and which the department checks. A defective invoice can cost your buyer their credit and expose you on scrutiny — so getting the fields right isn’t clerical, it’s commercial.

Mandatory fields on a tax invoice

• Your name, address and GSTIN
• A consecutive invoice number and date
• Buyer’s name, address and GSTIN (for B2B)
• HSN/SAC code for each item
• Description, quantity, value and taxable value
• Tax rate and amount, split into CGST+SGST or IGST
• Place of supply (for inter-state), and reverse-charge note where applicable
• Signature/digital signature of the supplier

Tax invoice vs bill of supply

A registered regular taxpayer issues a tax invoice showing GST. A composition dealer, or someone supplying exempt goods, issues a bill of supply instead — no GST shown, and no credit for the buyer. Issuing the wrong document type (a bill of supply where a tax invoice was needed) is a common error that breaks the buyer’s credit chain.

Time limits and the credit link

Invoices must be issued within prescribed time limits — for goods, generally at or before removal/delivery; for services, within 30 days of supply. Late or missing invoices delay your buyer’s credit and complicate your GSTR-1. Correct, timely invoicing (which our free billing software enforces) keeps the whole chain clean.