ISIN

Definition

An International Securities Identification Number (ISIN) is a 12-character code defined by ISO 6166 and allocated by each country's national numbering agency. It is made up of a two-letter country prefix, a nine-character national identifier and a check digit computed with the Luhn algorithm. IE00B4L5Y983 identifies exactly one share class of one ETF: the iShares Core MSCI World UCITS ETF USD (Acc). The distributing class, a hedged class or the same strategy from a different fund house each have their own ISIN.

Why it matters

Tickers change with the exchange and CUSIP, SEDOL and WKN are national, but the ISIN is global and printed on every factsheet, KID, contract note and custody statement. It is the identifier regulators use in transaction reporting and the one every fund data API accepts as input. Storing ISINs as your primary key avoids most reconciliation problems.

In the API

The ISIN is the only input: GET /api/v1/funds/{isin}. The response echoes it at top level and may include ISINs of underlying holdings inside topHoldings. Example values:

json
{
  "isin": "IE00B3RBWM25",
  "name": "Vanguard FTSE All-World UCITS ETF USD Dist",
  "cached": true,
  "data": { "securityType": "ETF" }
}

A malformed code returns 400 invalid_isin; a well-formed code that does not correspond to a fund returns 404 fund_not_found.

Common pitfalls

Validate format and check digit client-side before spending a request. Normalise to upper case and strip whitespace. Never treat the ISIN as a number: letters may appear in positions 3 to 11, and leading zeros are significant.