What makes a document a GST tax invoice, and not just a bill

In everyday conversation, a business owner asking a supplier for a bill and one asking for a tax invoice are often treated as asking for the same thing. Under GST law they are not, and the difference is not cosmetic. Section 31 of the Central Goods and Services Tax Act, 2017 requires a registered person supplying taxable goods or services to issue a tax invoice — a specific, defined document showing the description, value and the tax actually charged. The same section, at 31(3)(c), requires a registered person making an exempt supply, or one who has opted into the composition scheme, to issue a bill of supply instead — a document that does not show tax charged, because none is being collected on it.

A third document exists alongside both of these: an ordinary bill or cash memo issued by someone who is not registered under GST at all, or by anyone for a purely informal record. That document has no legal standing under GST law whatsoever, no matter how official it looks or how carefully it is formatted. Three documents, three different legal statuses, and only one of them is a tax invoice.

A document can carry a supplier's GSTIN and still fail to qualify as a valid tax invoice, because Rule 46 of the CGST Rules, 2017 sets out a specific list of particulars a tax invoice must contain. In broad terms, and not necessarily an exhaustive list, that includes the supplier's name, address and GSTIN; a consecutive serial number, unique for the financial year, of no more than sixteen characters; the date of issue; the recipient's name, address and GSTIN where the recipient is registered; the HSN or SAC code and description of what is being supplied; the quantity; the taxable value after any discount; the applicable tax rate; the tax amount, shown separately by central tax, state tax, integrated tax or cess as the transaction requires; the place of supply for an interstate movement of goods; and a signature or digital signature of an authorised person.

Missing even one required particular is a real defect, not a minor formatting slip — it is the specific set of particulars, taken together, that is what the law recognises as a tax invoice at all. A document that looks professionally printed but is missing, say, the HSN code or a proper sequential invoice number is not a lesser version of a tax invoice. Under the Rule, it simply is not one.

Worth being plain about here: preparing a GST-compliant tax invoice — validating a GSTIN, applying a numbering scheme, generating the document itself — is not something Khata does today. Its ledger records a transaction once a document has already been issued or received; it does not issue one. That is stated directly as a roadmap item, not a built feature, at automixai.in/docs/khata, which is a more useful thing for this article to say plainly than to leave a reader assuming otherwise.

A tax invoice's defining feature, beyond its particulars, is that it shows the tax charged as its own separate line, split by tax head — central tax and state tax for a supply within one state, or integrated tax for a supply across states. To make this concrete without quoting any real rate for any real good or service, an illustrative supply with a taxable value of INR 50,000.00, taxed at nine percent central tax and nine percent state tax, would show central tax of INR 4,500.00 and state tax of INR 4,500.00, for a total invoice value of INR 59,000.00.

That worked figure is purely illustrative arithmetic, not a rate this article is asserting for any actual supply — GST rates vary by the HSN or SAC classification of what is being supplied and change by government notification, so a reader needs the rate that actually applies to their own transaction, not a number borrowed from an example. What the example is meant to show is the shape a real tax invoice has to take: taxable value and tax shown as genuinely separate figures, not folded into one undifferentiated total the way an ordinary bill would present it.

A composition-scheme dealer or a supplier of exempt goods or services is legally prohibited from charging GST separately to a customer at all — that restriction is part of the trade-off of being under the composition scheme in the first place. The document such a supplier issues is required to be a bill of supply, not a tax invoice, and it never shows a tax line, because none was collected. It can carry a GSTIN, a serial number and a description that look, at a glance, much like a tax invoice's particulars.

The absence of a tax line is not a cosmetic difference. It is the entire legal distinction, and it has a direct financial consequence for whoever receives the document, covered next.

Claiming input tax credit depends, among other conditions this article does not attempt to enumerate exhaustively, on the buyer holding a valid tax invoice for the supply. A bill of supply carries no tax charged, so there is nothing on it for a buyer to claim credit for in the first place — that is simply how the composition scheme works, not an oversight. A document from a supplier who was never GST registered at all carries no ITC eligibility either, no matter how closely it resembles a proper invoice in appearance.

A buyer holding a document that looks like a tax invoice but is missing one of the particulars Rule 46 requires is in a genuinely uncertain position — the defect is real, even if it looks minor to someone glancing at the page. This is exactly the kind of gap worth catching at the point a document is received into the books, not months later when a credit claim is questioned.

The turnover threshold for compulsory GST registration, the threshold for opting into the composition scheme, and the threshold above which e-invoicing becomes mandatory have all been revised more than once by government notification since GST began in 2017, and the e-invoicing threshold in particular has been lowered repeatedly as it has been rolled out to smaller businesses. This article deliberately does not state a current figure for any of these thresholds, because a remembered number that has since changed is worse than no number at all — it reads with exactly the same confidence whether it is current or three revisions out of date.

Before relying on a specific threshold, a registration requirement, or whether e-invoicing applies to a particular business, the only reliable move is to check the current figure directly on the GST portal or with an accountant at the time it actually matters — not to trust a number, including one printed here, that was correct on the day it was written.