GSTIN
What GSTIN means, how it works, a worked example, the mistakes we see and the questions founders ask.
DefinitionA GSTIN is the 15-character Goods and Services Tax Identification Number issued to each registered business in each state, built from the state code, the PAN, an entity digit and a check character.
The first two characters of a GSTIN are the state code, the next ten are the business's PAN, the thirteenth counts registrations under the same PAN in that state, the fourteenth is Z by default, and the last is a checksum. One PAN can therefore hold several GSTINs, one per state where the business has a place of supply. You get it within about a week of applying on the GST portal, or through AGILE-PRO-S at incorporation, once the officer approves and Aadhaar authentication is done. You meet it on every tax invoice, in every return, on your signboard and on vendor forms. What it means for you: a GSTIN commits you to filing returns from the month of registration, so apply when you need it, not before, and cancel it properly if you stop the business.
How GSTIN works
The GSTIN is built from the business's PAN, which is why a sole proprietor's GSTIN carries their personal PAN and a company's carries the company's. The 15 characters read: two digits for the State code (27 Maharashtra, 29 Karnataka, 07 Delhi), the ten-character PAN, one character for the number of registrations the PAN holds in that State (1 for the first), the letter Z by default, and a check digit.
Registration is mandatory once aggregate turnover crosses ₹40 lakh for goods (₹20 lakh in the special category States) or ₹20 lakh for services (₹10 lakh in those States), and from the first rupee for interstate supply of goods, e-commerce sellers on platforms that collect tax, and anyone liable under reverse charge. A business can register voluntarily below the threshold to claim input credit, and many startups do.
One PAN can hold a GSTIN in every State it operates from, and each GSTIN files its own returns. The registration certificate (Form REG-06) must be displayed at the principal place of business and the GSTIN printed on every tax invoice and the name board. Cancellation is applied for on REG-16 when the business closes or falls below the threshold, with a final return on GSTR-10.
A Mumbai company with PAN AABCX1234Y registers in Maharashtra and receives 27AABCX1234Y1Z5. When it opens a warehouse in Bengaluru and starts supplying from there, it takes a second registration, 29AABCX1234Y1Z3, and files GSTR-1 and GSTR-3B separately for each. Stock moved between the two is a taxable supply between distinct persons, invoiced from one GSTIN to the other.
Mistakes we see with GSTIN
- Registering in one State and supplying from a warehouse in another under the same GSTIN; each place of supply needs its own registration.
- Quoting the GSTIN on invoices with a typo, so the customer's input credit fails to match in GSTR-2B and the payment is held back.
- Leaving a dormant GSTIN alive, which keeps accruing nil-return obligations and late fees until it is cancelled.
Last updated 19 October 2026. Checked against the MCA, GST, Income-tax and Trade Marks rules in force for October 2026.
Where you will meet this term
Questions founders ask about GSTIN
What do the 15 characters of a GSTIN mean?
Characters 1 and 2 are the State code, 3 to 12 the PAN, 13 the entity number for that PAN in that State, 14 is Z, and 15 is a check digit computed from the rest.
When is GST registration compulsory?
When aggregate turnover across India exceeds ₹40 lakh for goods or ₹20 lakh for services (half those figures in the special category States), and regardless of turnover for interstate supply of goods, sales through a tax-collecting e-commerce platform, reverse charge liability and a few other cases.
Can one business have two GSTINs?
Yes. One per State from which it supplies, and optionally separate registrations for distinct business verticals within a State. Each files its own returns.