SEDOL
SEDOLs are seven-character London-issued codes that embed directly into GB and IE ISINs as the nine-character NSIN.
SEDOL, the Stock Exchange Daily Official List code, is the seven-character identifier for securities traded in the United Kingdom and Ireland, issued by the London Stock Exchange. Six alphanumeric characters name the instrument and a seventh is a weighted check digit. For British and Irish securities the SEDOL becomes the NSIN inside the ISIN: prefix GB or IE, pad the SEDOL with two leading zeros to fill the nine-character field, then append the ISIN check digit. That direct embedding makes SEDOLs essential when reconciling London feeds against global holdings files, and it is why SEDOL-to-ISIN conversion is trivial once the check digits validate.