How to check whether a GST invoice is genuine

The short answer: a GST invoice can be checked by verifying six things — that the supplier's GSTIN is valid and active, that the invoice carries every particular Rule 46 requires, that the tax rate is one of the notified slabs, that the HSN or SAC code fits the goods or service, that the invoice number and date are within the permitted format and window, and that the supplier has actually reported the invoice in their return. The first five you can check from the invoice itself in a couple of minutes. The sixth needs the GST portal.

Fabricated invoices circulate for two reasons: to claim input tax credit that was never paid, and to extract payment for goods or services that were never supplied. Either way the person holding the invoice carries the loss, which is why it is worth a few minutes before you pay or claim against one.

1. Verify the GSTIN — structure, then status

A GSTIN is exactly 15 characters: a 2-digit state code, a 10-character PAN, one entity code, the letter Z, and a checksum character derived from the preceding fourteen. A number invented at random almost never satisfies that checksum, so a structurally invalid GSTIN is the single strongest signal that an invoice is not genuine.

Structure alone is not enough, though. Search the GSTIN on the GST portal's Search Taxpayer page — it is public and needs no login — and confirm three things: the registration is Active rather than cancelled or suspended, the legal name matches the name printed on the invoice, and the state matches the first two digits.

2. Check the mandatory particulars

Rule 46 of the CGST Rules lists what a tax invoice must contain, and a fabricated document usually omits something. The ones most often missing: place of supply with the State named, the HSN or SAC code, whether tax is payable on reverse charge, and a signature or digital signature.

The full list is in the Rule 46 guide. An invoice missing a mandatory particular is not a valid tax invoice regardless of whether it was issued in good faith.

3. Check the tax rate is a notified slab

GST rates come from a fixed set of notified slabs. A rate outside that set — an arbitrary 15%, or an effective figure produced by working backwards from a round total — is not something a compliant billing system produces. Fabricated invoices frequently carry a rate chosen to make the total look tidy.

4. Check the HSN or SAC code fits

Every line should carry an HSN code for goods or a SAC for services, at the number of digits the supplier's turnover requires. Two things to look for: a code that does not exist, and a code that exists but has nothing to do with what is being billed. The second is more common — a plausible-looking code copied from another invoice, attached to an unrelated product.

5. Check the invoice number and date

An invoice number may be at most 16 characters, must be unique within the financial year, and is restricted to letters, digits, hyphen and slash. A number longer than that, or containing other punctuation, did not come from a compliant system.

On dates, two things are worth a look: an invoice dated in the future, and an invoice dated before the supplier's registration took effect — the registration date is visible on the portal alongside the GSTIN.

6. Check the supplier actually reported it

This is the one that cannot be done from the invoice, and it is also the one that decides your input tax credit. Under Section 16(2)(c) of the CGST Act, credit depends on the tax having actually been paid to the government. An invoice can be perfect on its face and still leave you with nothing if the supplier never reported it.

The practical check is whether the invoice appears in your GSTR-2B for the relevant period. If it does not, the supplier has not reported it, and no amount of verification of the paper will change that.

A shortcut: the e-invoice QR code

Suppliers above the e-invoicing turnover threshold must obtain an Invoice Reference Number from the Invoice Registration Portal, and the invoice must carry a signed QR code. If the supplier is within that net, the presence of a valid IRN and QR is strong evidence the invoice is real, because it means the invoice was registered with the government at the moment it was issued. Its absence, on a supplier who should have one, is a serious red flag.

What a fabricated invoice usually gets wrong

• A GSTIN that fails the checksum, or belongs to a cancelled registration.
• Tax that does not reconcile — taxable value × rate not matching the tax shown.
• CGST and SGST that are not equal halves of the total tax.
• A missing place of supply, or one inconsistent with the tax heads charged.
• An invoice number that is too long, or in a format no billing system produces.
• Round-number totals arrived at by adjusting the tax rather than the price.

If an invoice fails these checks

1. Do not pay it, and do not claim credit against it, until the supplier has explained the discrepancy.
2. Ask for a corrected invoice in writing. A genuine supplier with a data-entry error will reissue without argument; that response is itself informative.
3. Check whether other invoices from the same supplier share the defect. A wrong GSTIN in their master repeats on every document.
4. If you believe the invoice is deliberately fabricated, it can be reported to the GST authorities through the grievance facility on the GST portal.

Checking this automatically

Five of the six checks above read only the invoice: the GSTIN structure, the mandatory particulars, the rate, the HSN, and the numbering and dates. Those are mechanical, and doing them by hand across three different websites is what makes people skip them.

You can run all five at once with the invoice verification check, or a whole batch of supplier invoices with the vendor invoice check. The sixth — whether the supplier reported it — genuinely requires the portal, and no tool that reads only the invoice can tell you otherwise.