GSTIN validator
Check whether a GST number is well-formed, and see the state, PAN and holder type it encodes. Everything runs in your browser.
Type or paste a 15-character GSTIN. Checking happens in your browser — nothing is uploaded.
Provided for quick reference and general guidance. Tax rules change and edge cases exist — confirm anything consequential with your CA or the GST portal before acting on it.
What a GSTIN actually encodes
A GSTIN is not a random string — it is fifteen characters with a fixed structure, and most of it is derived from information you may already have. The first two digits are the state code. The next ten characters are the entity's PAN. The thirteenth is a registration counter, distinguishing multiple registrations by the same PAN within one state. The fourteenth is 'Z' by current convention, and the fifteenth is a checksum.
That checksum is what makes validation possible offline. It is computed from the preceding fourteen characters using a mod-36 scheme with alternating weights, so a single mistyped character will almost always produce a mismatch. This tool catches every single-character typo we tested it against — all 490 possible mutations of a valid GSTIN.
There is an important limit to that. A structurally valid GSTIN is one that could exist; it is not proof that the number is registered, active, or belongs to the business quoting it. Only the GST portal can confirm registration status. Use this to catch typos before they reach an invoice — which is where a wrong GSTIN becomes an input-credit problem for your customer.
Frequently asked questions
Does a valid result mean the business is GST registered?
No. This confirms the number is well-formed — the pattern is right, the state code exists, and the checksum matches. It cannot confirm the GSTIN is currently registered or active, or that it belongs to the business quoting it. Verify registration status on the GST portal.
Is my GSTIN sent to a server?
No. Validation runs entirely in your browser using JavaScript on this page. Nothing is uploaded, logged or stored.
What do the parts of a GSTIN mean?
Characters 1–2 are the state code, 3–12 are the PAN of the entity, 13 is the registration number for that PAN within the state, 14 is 'Z' by convention, and 15 is a checksum computed from the first fourteen.
Why does the checksum matter?
It makes typos detectable. Because the last character is derived from the other fourteen, mistyping any one of them breaks the relationship. Catching that before it reaches an invoice matters — a wrong GSTIN on a tax invoice can cost your customer their input tax credit.
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