CUSIP

GET/v0/cusip

Validates a CUSIP (Committee on Uniform Security Identification Procedures) identifier — the 9-character code used to identify financial instruments in the United States and Canada. A CUSIP consists of a 6-character issuer number, a 2-character issue number, and a 1-digit check digit computed using a modified Luhn algorithm with a character-to-number mapping that covers digits 0–9, letters A–Z, and special characters *, @, and #. Whitespace in the input is stripped automatically.

For US and Canadian ISINs the NSIN is identical to the CUSIP, so the /v0/isin endpoint also returns a cusip field derived from the ISIN NSIN when the country code is US or CA.

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Query Parameters

Parameter	Type	Required	Description
value	string	Yes	The 9-character CUSIP to validate (e.g. `037833100`)

Example Request

curl -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.isvalid.dev/v0/cusip?value=037833100"

Response Fields

Field	Type	Description
valid	boolean	Whether the CUSIP passed format and check digit validation
issuerNumber	string	First 6 characters identifying the issuer, assigned by the CUSIP Global Services bureau
issueNumber	string	Characters 7–8 identifying the specific issue (share class, bond series, etc.)
checkDigit	string	The check digit (9th character, always a digit 0–9)

Example Response

{
  "valid": true,
  "issuerNumber": "037833",
  "issueNumber": "10",
  "checkDigit": "0"
}

Example Response — invalid

{
  "valid": false
}