What is a GSTIN, and how do I check one?
Fifteen characters that encode the state, the PAN and a check digit you can verify yourself.
Last checked 20 September 2026
A GSTIN is the 15-character number that identifies a GST-registered business. It is built from a 2-digit state code, the holder’s 10-character PAN, a registration number within that state, a fixed letter, and a check digit — so the format alone tells you a great deal, and an obviously wrong number can be caught before you bill.
Reading a GSTIN
Take 22AAAAA0000A1Z5 and break it up:
| Position | Example | What it is |
|---|---|---|
| 1–2 | 22 | State code. 22 is Chhattisgarh, 27 Maharashtra, 07 Delhi, 33 Tamil Nadu, and so on |
| 3–12 | AAAAA0000A | The PAN of the business |
| 13 | 1 | How many registrations this PAN holds in this state |
| 14 | Z | Fixed, by design |
| 15 | 5 | Check digit, calculated from the other fourteen |
Two useful consequences. The first two digits are the state, so a GSTIN that starts 27 belongs to a Maharashtra registration whatever address is printed on the letterhead. And the PAN is embedded, so a GSTIN and a PAN that do not match belong to different entities.
GSTIN Validator — free, no signupCheck the format and the check digit of one GSTIN, or paste a whole column of them.What a check digit does and does not prove
The fifteenth character is computed from the first fourteen. It catches mistyping, transposed characters and invented numbers instantly, and it can be verified offline, in your browser, with no lookup.
A valid format is not a valid registration
A number can pass the checksum and still belong to a registration that is cancelled, suspended, or simply not the business in front of you. For anything that matters, look the GSTIN up on the GST portal and check the legal name and status against who you are actually dealing with.
Why it is worth getting right
- Your buyer’s credit depends on it. A wrong GSTIN on their invoice means the supply is reported against someone else, and the credit does not reach them.
- Reconciliation breaks. Mismatches between your records and what appears in GSTR-2B are one of the most common causes of lost credit. See GSTR-2B reconciliation.
- It is much harder to fix later. Correcting a reported invoice means amendments and explanations. Checking fifteen characters takes seconds.
Where to store it
On the party record, once, validated on entry — not typed fresh onto each invoice by whoever is at the counter. In TracEasy it lives on the party and flows onto every bill; see add a party.
Can one business have several GSTINs?
Yes. Registration is state by state, so a business operating in five states holds five GSTINs against the same PAN. The 13th character distinguishes multiple registrations within one state.
What is a UIN?
A Unique Identity Number, issued to bodies such as embassies and UN agencies that are not ordinary taxpayers but can claim refunds. It occupies the same field on an invoice as a GSTIN.
My customer refuses to give a GSTIN. Can I still bill them?
Yes — they are then treated as unregistered. Note that for an unregistered buyer where the invoice value crosses ₹50,000 the rules require you to record their name, address and state on the invoice.
Sources
Free tools for this
How TracEasy handles this
Related reading
What is GST?
One tax on the supply of goods and services, charged at every stage but paid only on the value added.
GST invoice format: what must be on the bill
The fields Rule 46 requires, with a worked example of each.
What is input tax credit?
The tax you paid on purchases, set against the tax you collected on sales.