GSTIN Validator

GSTIN search & format validator.

Paste a GST number to check its 15-character format and checksum digit. This is an offline format check, not a live portal lookup — for registration status, use the official GST portal.

Updated July 2026
Built by CA Anil Agarwal

GSTIN

15 characters — state code, PAN, entity code, default 'Z', checksum digit.

What this checks

The 15-character structural pattern (state code, PAN shape, entity code)
The checksum (15th character) using the standard GSTIN algorithm

This is a format and checksum check only — it does not confirm the GSTIN is actually registered or active. For live registration status, use the official GST portal search.

Result

Enter a GSTIN to check its format and checksum.

Validate every GSTIN before it hits an invoice.

TatvaBooks checks the GSTIN format and checksum the moment you add a customer or vendor, so a typo never turns into a rejected e-invoice or a mismatched GSTR-2B entry.

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How it works

What a GSTIN means, character by character.

The 15-character structure

A GSTIN is always 15 characters: characters 1-2 are a numeric state code assigned by the Government (e.g. 27 for Maharashtra, 09 for Uttar Pradesh, 07 for Delhi). Characters 3-12 are the taxpayer's 10-character Income Tax PAN — 5 letters, 4 digits, 1 letter. Character 13 is an entity code, used when the same PAN holder has more than one GST registration within the same state. Character 14 is fixed as the letter Z by default (reserved for future use). Character 15 is a checksum character, computed from the preceding 14 characters using a mod-36 algorithm, so that a single mistyped character anywhere in the GSTIN will almost always produce a mismatch.

Format check vs. live lookup

This tool runs the pattern match and checksum calculation entirely in your browser — no data is sent anywhere, and nothing is looked up against a government database. That makes it fast and private, but it also means a GSTIN can pass this check and still not correspond to a real, active registration (for example, if it was cancelled, suspended, or never actually issued). For that, use the official GST portal's Search Taxpayer tool, which queries the live GSTN database and returns legal name, registration date, and filing status.

Why this matters for invoicing

A malformed or mistyped customer/vendor GSTIN is one of the most common causes of e-invoice rejection and GSTR-2B/ITC mismatches. Catching the typo at data-entry time — before the invoice is generated and reported — saves a reconciliation headache later. See our GST registration guide for how GSTINs are issued in the first place.

Frequently asked questions

GSTIN validator — common questions.

What does this GSTIN validator actually check?

It checks two things offline, in your browser: (1) that the GSTIN matches the 15-character structural pattern — 2-digit state code, 10-character embedded PAN, entity code, the fixed 'Z', and a checksum character — and (2) that the checksum character is mathematically correct for the first 14 characters, using the standard GSTIN checksum algorithm. It does not check whether the GSTIN is actually registered, active, or belongs to a real taxpayer.

How do I check if a GSTIN is actually registered and active?

Use the official GST portal's 'Search Taxpayer' tool at gst.gov.in/services/searchtp. That queries the live GSTN database and shows registration status, legal name, registration date, and filing status. This page only validates format and checksum — it is a fast first filter to catch typos before you look up the live status.

What do the 15 characters of a GSTIN mean?

Characters 1-2 are the state code (numeric, e.g. 27 for Maharashtra, 07 for Delhi). Characters 3-12 are the entity's 10-character PAN (5 letters, 4 digits, 1 letter). Character 13 is an entity code — distinguishes multiple GST registrations under the same PAN in the same state. Character 14 is fixed as 'Z' by default. Character 15 is a checksum digit computed from the first 14 characters, used to catch data-entry errors.

Why would a GSTIN fail the checksum check but look correctly formatted?

This usually means one character was mistyped or transposed somewhere in the first 14 characters, or the last character itself was copied wrong. The checksum algorithm is sensitive to every character's position, so even a single-character typo anywhere in the GSTIN will produce a checksum mismatch. Re-check the source document (invoice, GST certificate) character by character.

Can two businesses have the same PAN in different GSTINs?

Yes. A single PAN holder can register in multiple states (each gets its own GSTIN with a different state code) and can also take multiple registrations within the same state for different business verticals, distinguished by the entity code (character 13). All these GSTINs share the same 10-character PAN embedded in characters 3-12.

Books that validate a GSTIN the moment you type it.

TatvaBooks checks format and checksum inline on every customer and vendor record, and flags e-invoice-blocking errors before they cost you a rejected IRN.

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