A Crest Depository Interest (CDI) is a UK financial security that represents a stock traded on a stock exchange outside the UK. CDIs are issued by CREST, and one CDI is the equivalent of one share of an eligible foreign stock.
Under UK law, actual international shares cannot be dealt directly through CREST, and so the CDIs allow investors to trade in some foreign stocks. CDIs can be settled through CREST like a regular UK share. CDIs are not traditionally listed on the London Stock Exchange, and are traded off-exchange.