(3)CSDs are instrumental to financial markets. The recording of securities in a book-entry system (‘notary services’) and the maintenance of securities accounts at the top tier level (‘central maintenance services’) increase transparency and protect investors, as they ensure the integrity of the issue and prevent undue duplication or reduction of securities. CSDs also operate securities settlement systems, which ensure that securities transactions are settled properly and in a timely manner. These functions are critical in the post-trade clearing and settlement process and as such essential to the financial stability of the Union and its Member States. Securities settlement systems are essential also to monetary policy as they are closely involved in securing collateral for monetary policy operations. Furthermore, market operators in Ireland rely on the services of a UK CSD with respect to corporate securities and exchange traded funds constituted under the domestic law of Ireland.