It operates the CREST system, whose name stands for Certificateless Registry for Electronic Share Transfer.
CREST also serves a number of other important functions, such as assisting in the payments of dividends to shareholders.
In the event that transaction details do not match, CREST will highlight the issues and ensure that the problems are resolved as soon as is practicable.
Members are usually pension funds, inter-dealer brokers or other large financial institutions with significant resources.
UK stocks are held by registrars who are members of CREST and are therefore integrated into the transfer of ownership.
This is because a CDI is an electronic reflection of the underlying security held in the domestic (country of origin) market.
Restrictions apply, only securities that have a UK quote can be transferred to CREST's DTC account.
HMRC consider that a CDI is a chargeable security for the Stamp Duty Reserve Tax.