GSTIN
The 15-character registration number a business gets when it registers under GST.
What it means in business
Every registered taxpayer has a GSTIN for each state it is registered in. The first two digits are the state code, the next ten are the business's PAN, and the last characters identify the registration and check the number. It appears on every tax invoice, return and e-way bill, and it is how the GST system recognises who supplied what to whom.
Example
A manufacturer in Gujarat and a branch in Maharashtra have two different GSTINs, both built on the same PAN. A purchase from the Maharashtra branch is entered against that branch's GSTIN, not the Gujarat one. This is an illustration of normal business use rather than a quoted case study.
How to use it correctly
Check a customer's or supplier's GSTIN on the GST portal before you raise or accept an invoice, and store it in the party master exactly as it appears. A wrong GSTIN on a sale means the buyer cannot claim credit on it, and a wrong one on a purchase means you may not get yours.
Common confusion
A GSTIN is not the same as a PAN or an Udyam number. The PAN is inside the GSTIN, but they are issued separately and used for different things. A business with a GSTIN in one state does not automatically have one in another.
Related glossary terms
Sources and further reading
Written on 24 October 2026 for lamp. Confirm the current rules with the official source or an adviser before relying on it.