How is a GSTIN structured?

15 characters — a 2-digit state code, the entity's 10-character PAN, a 1-character entity number, the reserved letter Z, and a base-36 check digit computed over the first 14 characters.

What is the PAN inside a GSTIN?

Characters 3 to 12 of the GSTIN are the holder's 10-character PAN (Permanent Account Number), in the pattern of five letters, four digits and one letter — for example AAAAA0000A.

What does the state code at the start mean?

The first two digits are the GST state code identifying the place of registration — for example 27 is Maharashtra, 29 is Karnataka, 22 is Chhattisgarh. The validator decodes it to the state name.

How is the GSTIN check digit calculated?

It is a base-36 check over the first 14 characters. Each character maps to 0-35 (0-9 then A-Z), is multiplied by an alternating factor of 1 and 2, and the quotient plus remainder of dividing each product by 36 are summed. The check value is (36 − sum mod 36) mod 36, mapped back to a character.

Why is the 14th character always Z?

The 14th character is currently reserved and set to the letter Z by default in the GSTIN scheme. The 13th character is the entity (registration) number for that PAN within the state.

Does a valid GSTIN mean the business is registered and active?

No. A pass confirms the number is well-formed — correct length, valid state code, valid PAN pattern, and matching check digit. Only a lookup on the official GST portal confirms an active registration.

Is my GSTIN sent anywhere?

No. The check digit is computed entirely in your browser — privacy-first, the GSTIN never leaves your device and no GST portal lookup is made.

What is the India GSTIN Validator?

Free India GSTIN validator. Check the 15-character GST Identification Number format — state code, embedded PAN and the GSTN base-36 check digit. Privacy-first and runs entirely in your browser — no GST portal lookup, nothing is sent anywhere. It runs free in your browser on Gera Tools, with nothing uploaded.

India GSTIN Validator

Name: India GSTIN Validator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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This tool validates the format of a 15-character India GSTIN (GST Identification Number). It decodes the state code, checks the embedded PAN, and recomputes the check digit offline — useful for catching typos on invoices and in vendor records before filing.

When GSTIN validation is needed

Under India’s GST regime, businesses must quote their GSTIN (and their suppliers’ GSTINs) correctly on every tax invoice. A wrongly typed GSTIN — even one character off — causes the recipient to fail Input Tax Credit (ITC) reconciliation on the GSTN portal, because the credit claimed will not match the credit uploaded by the supplier. Catching format errors before filing is far less painful than correcting mismatches after the fact.

This validator is also useful in procurement workflows: before registering a new vendor in an ERP, format-check their GSTIN to confirm it is at least structurally valid and that the state code corresponds to their stated registration state.

How it works

A GSTIN is 15 characters with a fixed structure:

Position	Length	Meaning
1–2	2	State code (e.g. 27 = Maharashtra)
3–12	10	Holder’s PAN (AAAAA0000A pattern)
13	1	Entity number for that PAN in the state
14	1	Reserved (currently Z)
15	1	Base-36 check digit

The validator decodes the state code to a name, verifies the embedded PAN pattern (five letters, four digits, one letter), and recomputes the GSTN base-36 check digit over the first 14 characters: each character maps to 0–35 (0–9 then A–Z), is multiplied by an alternating factor of 1 and 2, and the quotient and remainder of dividing each product by 36 are summed; the check value is (36 − sum mod 36) mod 36. It compares that to the 15th character.

Worked example

For 22AAAAA0000A1Z5:

State code 22 → Chhattisgarh
PAN = AAAAA0000A → matches the valid pattern (5 letters + 4 digits + 1 letter)
Entity number 1 — the first registration for this PAN in Chhattisgarh
Reserved character Z
Check digit recomputed over the first 14 characters and compared to 5

If the recomputed digit matches, the GSTIN is structurally well-formed.

GST state codes quick reference

Some frequently referenced codes: 07 = Delhi, 09 = Uttar Pradesh, 19 = West Bengal, 27 = Maharashtra, 29 = Karnataka, 33 = Tamil Nadu, 36 = Telangana. The validator decodes whichever state code is present in the first two characters.

What this tool does not check

A structurally valid GSTIN is not necessarily an active registration. A business may have cancelled, suspended, or never actually registered a number that passes the format check. To confirm active status, use the official GST portal’s “Search Taxpayer” function at gst.gov.in. This tool is privacy-first — no data is sent anywhere, and no portal lookup is made.