CUSIP

CUSIP is the nine-character identifier that dominates United States and Canadian securities data. Owned by the American Bankers Association and administered by the CUSIP Global Services bureau, it splits into six characters for the issuer, two for the specific issue, and a trailing check digit. You meet it constantly in US workflows: corporate actions, TRACE bond prints, DTCC settlement messages, and SEC 13F holdings files. Because the ISIN of a US security is just the country prefix US followed by the nine CUSIP characters and a new Luhn check digit, the two identifiers interlock neatly, and converting between them is a few lines of code.