GSTIN Explained: Structure, How to Verify a GST Number, Fake GST Red Flags and What to Check Before Paying

A GSTIN is a business's tax identity under GST. Every B2B invoice should carry one, and checking it before you deal with a new supplier can protect you from fake invoices, lost input tax credit and trouble with tax authorities. Verification takes a minute and is free. This guide explains the structure and how to check.

Fees, forms and procedures change often. Treat the figures here as indicative and confirm them on the official government or bank website before you act.

The 15-character structure

A quick format check helps spot obviously wrong numbers, but a number that passes the format check may still be invalid or cancelled. Use the GST number validator for a format check and then confirm on the official portal.

How to verify a GSTIN online

1. Open the official GST portal and use "Search Taxpayer" under the services menu.
2. Enter the GSTIN and the captcha.
3. Review the result: legal name, trade name, state, registration date, status (active, cancelled or suspended), type of taxpayer and the principal place of business.
4. Check the registration status and filing frequency. Most portals also allow you to look at the return filing status.

Match the legal and trade name on the portal with the name on the invoice and the bank account. If the names do not match, ask why.

Why verification matters

If your supplier's GSTIN is cancelled or fake, or if they do not file returns, you may lose your input tax credit, face a demand with interest and penalties, and your own registration may come under scrutiny. Read how credit works in our ITC guide.

Red flags of fake or risky suppliers

• GSTIN with the wrong state code, or format errors.
• Registered address that is a residence or does not exist, or looks like a shared mailbox.
• Invoices without proper HSN codes, sequential numbers or tax breakups.
• Prices much lower than the market in return for cash payment.
• Supplier reluctant to give bank details in the business name.
• Frequent non-filing of returns, shown on the portal.
• New registration with very high transactions.

What a valid tax invoice contains

• Supplier name, address and GSTIN, and recipient name, address and GSTIN for B2B.
• Invoice number and date, a unique running number.
• Description of goods or services, HSN or SAC code, quantity and taxable value.
• Rates and amounts of CGST, SGST, IGST or UTGST, place of supply and total.
• Signature, and a QR code and IRN for businesses above the e-invoicing threshold.

E-invoicing and e-way bills

Larger businesses must generate e-invoices through the Invoice Registration Portal. Goods movement above a value threshold needs an e-way bill. You can verify these documents on the respective portals. Thresholds change, so check the current ones.

Due diligence for regular suppliers

1. Collect the GST registration certificate and check it against the portal.
2. Verify PAN with the PAN validator, and see our PAN guide.
3. Check the filing status periodically, at least quarterly.
4. Pay only to a bank account in the supplier's name.
5. Keep the invoice, e-way bill, proof of delivery and payment proof.

If you suspect a fake GSTIN

Do not claim ITC on those invoices. Report the matter on the GST portal's grievance mechanism or to the tax authorities, and consult a GST practitioner. If someone uses your GSTIN or PAN fraudulently, report it and keep records.

For return filing basics, read the GST return guide, and for calculations see GST calculation.

Using verification in your daily workflow

Make GSTIN checking a standard step in vendor onboarding rather than something you do after a problem. Add a checklist line to your purchase process: GSTIN verified on the portal, status active, name matches the invoice, and filing status reviewed. Record the date of the check and a screenshot or PDF in the vendor file. For high-value or recurring suppliers, repeat the check every quarter, because registrations can be suspended or cancelled after you start dealing with them. If you run an accounts team, give one person the responsibility of reviewing a monthly list of suppliers whose returns appear overdue. This small discipline costs a few minutes and can protect lakhs of rupees in input tax credit.

Frequently asked questions

What does a GSTIN look like?

A 15-character number combining a state code, PAN, entity number, the letter Z and a check character.

How do I verify a GSTIN?

Use the Search Taxpayer facility on the official GST portal.

Can a valid-looking GSTIN be cancelled?

Yes. Always check the registration status on the portal.

What if my supplier's GSTIN is fake?

Do not claim ITC and report the matter.

Is GSTIN the same as PAN?

No, but the GSTIN includes the PAN as part of its structure.

Do all invoices need a GSTIN?

B2B invoices must show the supplier's GSTIN, and the recipient's where applicable.

Last reviewed 8 November 2026. Rates, limits and rules change, so confirm figures with the official source before you act.