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GSTIN validator and PAN checker

Checksum in your browser

Paste a GSTIN to verify its check character and read the state, PAN and holder type inside it. Switch to PAN, IFSC, UPI ID, PIN code or Aadhaar (checksum only) to validate those formats too.

Try:
Paste up to 200; spaces and dashes are ignored. Nothing is sent or saved.
Drop a .txt or .csv file here, or· read in your browser, never uploaded
Runs in your browser. Ctrl+Enter also works.

Fill in the fields to see the result.

How to use it

  1. Pick GSTIN (or PAN, IFSC, UPI, PIN code, Aadhaar) in the number type.
  2. Paste numbers one per line or drop a file.
  3. Read valid or invalid with the reason; confirm registration on gst.gov.in for anything important.

Details

GSTIN
15 characters: state code, PAN, entity number, Z, mod-36 check character
PAN
5 letters, 4 digits, 1 letter; the 4th letter is the holder type
Aadhaar
12 digits with a Verhoeff checksum; checked locally and never stored
Not checked
Whether the GSTIN is active; use gst.gov.in Search Taxpayer

Questions

How is a GSTIN check digit calculated?

Each of the first 14 characters is mapped to a value 0-35, multiplied alternately by 1 and 2, and the quotient and remainder of each product by 36 are added. The 15th character is the one that makes the total divisible by 36.

Does valid mean the business is registered?

No, only that the GSTIN is well formed. Search it on gst.gov.in to see the legal name and whether the registration is active.

Can the PAN check letter be verified?

Not reliably: the algorithm for PAN's 10th character isn't published, so the tool checks the structure and holder type only.

Is it safe to check an Aadhaar number here?

Only the Verhoeff checksum is computed, in your browser. The number is never sent, logged, saved or put in the address bar.

Is what I type sent anywhere?

No. The calculation runs in this browser tab with the same code our MCP server uses. Nothing you type is sent to a server or saved, apart from settings like filing status, which stay in this browser.

Can an AI agent use this?

Yes. The same function is a tool on our free MCP server at tools.cuelark.com/mcp, so ChatGPT, Claude or Cursor get exactly the answer this page shows. 'Copy MCP call' gives you the arguments.