Six dimensions where a kaccha bill fails and a pakka bill (GST tax invoice) holds

A "pakka bill" in Indian trade parlance is a GST tax invoice — a document the law recognises. A "kaccha bill" is an informal slip: a hand-torn estimate, a delivery chit, a WhatsApp message. The two words describe the same transaction but produce opposite legal outcomes, and the gap shows up on six measurable dimensions. The matrix above sets them side by side so a buyer can audit which one they are holding.

The first dimension is **legal basis**. A tax invoice is mandated by Section 31 of the CGST Act — a registered supplier *must* issue one for a taxable supply. A kaccha bill has no statutory standing at all; it is not a category the GST law recognises. The second is the **seller GSTIN**: Rule 46 requires the supplier's GST identification number on the invoice, which identifies the seller in the GST system. Kaccha bills almost never carry it. The third is whether **GST is shown**: a pakka bill displays the rate and the tax amount split into CGST, SGST, or IGST; a kaccha bill shows a lump sum, if any tax is named at all.

The fourth dimension is the one that costs the buyer money: **input tax credit**. Under Section 16 of the CGST Act, a registered buyer can offset the GST paid on purchases against the GST they collect on sales — but only if they hold a valid tax invoice. A kaccha bill blocks ITC entirely, so the buyer eats the full tax as a cost. The fifth is **GST-audit standing**: a tax invoice reconciles to the supplier's GSTR returns, so it survives a departmental check; a kaccha bill has no return trail to reconcile against. The sixth is **expense proof** — a tax invoice is accepted as a deductible business cost, while a kaccha bill is weak and disputable when the income-tax officer asks for substantiation.

The practical takeaway for a business buyer is blunt: insisting on a pakka bill is not pedantry, it is the difference between recovering the GST and paying it twice. For a seller who is GST-registered, refusing to issue a tax invoice on a taxable supply is itself a breach of Section 31. The kaccha bill is convenient at the counter and expensive at the audit.