CUSIP

Definition

A CUSIP is a nine-character alphanumeric code that identifies securities in the United States and Canada. The first six characters identify the issuer, the next two the specific issue (a share class, bond or fund), and the ninth is a check digit. The system is operated by CUSIP Global Services on behalf of the American Bankers Association and takes its name from the Committee on Uniform Securities Identification Procedures.

A US ISIN is built directly from the CUSIP: the prefix US, the nine CUSIP characters, then an ISIN check digit. The same relationship holds for SEDOL inside UK and Irish ISINs.

Why it matters

US mutual funds and US-listed ETFs are identified by CUSIP in brokerage systems and regulatory filings, while European systems, UCITS documents and most fund APIs work with ISINs. Anyone building for both markets needs to convert one into the other, and the conversion is deterministic in one direction only: a CUSIP can be turned into a US ISIN by adding the prefix and computing the check digit, but an ISIN from another country has no CUSIP.

In the API

FundFacts API is keyed by ISIN, so a CUSIP must be converted before calling GET /api/v1/funds/{isin}. The response echoes the ISIN at top level; no separate CUSIP field is returned. Example values:

json
{
  "isin": "IE00B4L5Y983",
  "name": "iShares Core MSCI World UCITS ETF USD (Acc)",
  "data": { "securityType": "ETF" }
}

Common pitfalls

CUSIPs are licensed identifiers, so check redistribution terms before storing or displaying them. Ticker symbols are not CUSIPs and are not unique across exchanges; see ticker. Coverage of US-domiciled funds by European data sources is typically thinner than for UCITS funds.