What Is a GSTIN Number? Format, Registration, and Uses

A GSTIN number is the 15-digit Goods and Services Tax Identification Number assigned to every business registered under India’s GST system. It links your business to every invoice you issue, every return you file, and every rupee of Input Tax Credit you claim. If you sell goods and your annual turnover crosses ₹40 lakhs, or you supply services and cross ₹20 lakhs, registration is mandatory.¹

What the 15 Digits Mean

A GSTIN looks like 22AAAAA0000A1Z5, and each part of that string carries information you can read at a glance.

Digits 1–2 are the state code. 27 is Maharashtra, 07 is Delhi, 22 is Chhattisgarh.
Digits 3–12 are the business’s PAN, tying GST registration to the income tax identity.
Digit 13 is the entity number, showing how many registrations the same PAN holds in that state.
Digit 14 is almost always “Z” for regular taxpayers.
Digit 15 is a check character used to catch typos and confirm the number is valid.

Because the PAN sits inside the GSTIN, tax authorities can cross-reference GST compliance with income tax records without any extra lookup.

Who Needs to Register

The turnover thresholds are ₹40 lakhs for goods and ₹20 lakhs for services. In special category states, mostly in the northeast and the hills, the limits drop to ₹20 lakhs for goods and ₹10 lakhs for services.¹

Some categories must register regardless of turnover:

Inter-state suppliers, where the goods or services move between different states or union territories.
E-commerce operators and sellers using those platforms.
Non-resident taxable persons who occasionally transact in India without a fixed place of business here.
Recipients liable under reverse charge, such as businesses receiving legal services from advocates or hiring goods transport agencies.²

You can also register voluntarily below the threshold. The usual reason is Input Tax Credit: without a GSTIN, you cannot offset the GST you pay on purchases against the GST you collect on sales. B2B customers prefer registered suppliers for the same reason, because only then can they claim ITC on what they pay you. For a small B2C seller with low input costs, the compliance load may outweigh the benefit.

The Composition Scheme

Businesses with turnover up to ₹1.5 crore (₹75 lakhs in special category states) can opt for the Composition Scheme instead of regular registration. Composition dealers pay a flat percentage on turnover: 1% for traders and manufacturers, 5% for restaurants that don’t serve alcohol, and 6% for service providers.

The trade-off matters. Composition dealers cannot collect GST from customers, cannot claim ITC, and cannot make inter-state sales. They must display a notice at their premises stating they are not entitled to collect tax. For a shop that sells within one state and buys little that carries input GST, the simpler paperwork can be worth it.

How to Register

Registration happens on the GST portal at gst.gov.in. The government charges no fee. Before starting, pull together:

The PAN card of the business entity or proprietor.
Business registration proof, such as a partnership deed or certificate of incorporation.
Address proof for the premises: utility bill, rental agreement, or property tax receipt.
A bank statement or cancelled cheque.
Aadhaar and photographs of all authorized signatories.

The portal’s document advisor tool will tell you exactly which papers your entity type requires.³

You start by generating a Temporary Reference Number through an OTP sent to your registered mobile. The OTP is valid for 10 minutes, so keep your phone close. Using the TRN, you log back in and complete Form GST REG-01, which covers business details, promoter or partner information, and document uploads. After submission the system issues an Application Reference Number by email and SMS, which you can use to track status.⁴

Under the simplified system that took effect in November 2025, most clean applications receive automatic approval within three working days. If the tax officer spots a discrepancy, they issue a notice asking for clarification, and that extends the timeline.

What You Do With a GSTIN

Once issued, your GSTIN appears on every tax invoice you raise, on your business signboard, and on your registration certificate kept visible at your premises. Customers can then check whether you are actually authorized to collect GST.

Filing Returns

Registered taxpayers file periodic returns even in months with no transactions. The two core returns are GSTR-1, which reports your outward supplies in detail, and GSTR-3B, a summary return where you declare liability, report purchases, claim ITC, and pay tax.⁵ Filing a nil return when you had no activity is mandatory; skipping it triggers late fees.

If your aggregate turnover is up to ₹5 crore, you can opt into the Quarterly Return Monthly Payment (QRMP) scheme. You file GSTR-1 and GSTR-3B quarterly while paying tax monthly through challan GST PMT-06. That takes you from 24 detailed returns a year down to 8.

Input Tax Credit

ITC is the practical payoff of registration. GST you pay on raw materials, supplies, and services can be subtracted from the GST you collect on sales, so only the difference goes to the government. Without a GSTIN, that offset is not available and you absorb the full input GST.

Verifying Suppliers

The GST portal has a search tool for checking any GSTIN. You can see whether it is active, the business name attached to it, and the state of registration. Run this check before large orders with a new supplier: if their registration is suspended or canceled, ITC you claim on that purchase can be denied.

E-Way Bills

When you move goods worth more than ₹50,000 across state lines, you must generate an e-way bill through the GST system before the shipment leaves. Intrastate thresholds vary by state; many have raised the limit to ₹1 lakh, while others keep ₹50,000. Your GSTIN is required to generate the bill, and moving goods without one when it’s required exposes the shipment to seizure and penalties.

Penalties for Not Registering

Under Section 122 of the CGST Act, operating without registration when you should have registered carries a penalty of ₹10,000 or the amount of tax that should have been paid, whichever is higher. You also owe the back tax for the entire unregistered period, plus interest at 18% per year on the unpaid amount.

Late filing after registration costs ₹50 per day for GSTR-3B, or ₹20 per day if the return has nil tax liability. The daily rate adds up fast across missed months.

Willful evasion with evaded tax above ₹5 crore can lead to criminal prosecution, with imprisonment from six months to five years along with a fine. That threshold is high enough that most small businesses will never see criminal exposure, but the civil costs alone make timely registration the cheaper path.

Canceling a GSTIN

If your business closes, your turnover drops below the threshold, or your structure changes in a way that requires a new PAN, you can apply to cancel through the portal. Recognized grounds include closure, transfer by sale or merger, a change in constitution requiring a new PAN, and the death of a sole proprietor.⁶

You log in, open the cancellation application, select a reason, and declare any remaining stock along with the tax on it. If you hold inventory at cancellation, you must pay GST on the stock value or reverse the ITC previously claimed on it, whichever is higher. The amount can be settled from your electronic credit or cash ledger.⁶

Tax authorities can also cancel on their own, usually for continuous non-filing or fraudulent registration. A cancellation by the department does not wipe out your obligation to pay outstanding taxes and file pending returns for the period your registration was active.

1
CBIC Tax Information Portal. CGST Act – Section 22: Persons Liable for Registration
2
GST Council. Reverse Charge Mechanism
3
GST Portal. GST Document Advisor
4
GST Portal. Apply for Registration Normal Taxpayer
5
GST Portal. Create and Submit GSTR-3B
6
GST Portal. Cancellation of Registration Manual