To allow transparency and comparability of contractual arrangements and the ongoing monitoring of those arrangements, the register of information should focus on the operational links between the financial entitiesas defined in Article 2, points (a) to (t) and the ICT third-party service providersmeans an undertaking providing ICT services;. To that end, the register of information should use four keys, which, among others, linking relevant data to each other across the templates of the register of information: (i) the reference number of the contractual arrangement between the financial entity signing that arrangement and the direct ICT third-party service providermeans an undertaking providing ICT services;, (ii) an appropriate identifier of financial entitiesas defined in Article 2, points (a) to (t) and ICT third-party service providersmeans an undertaking providing ICT services;, (iii) the function identifier, and (iv) the type of ICT servicesmeans digital and data services provided through ICT systems to one or more internal or external users on an ongoing basis, including hardware as a service and hardware services which includes the provision of technical support via software or firmware updates by the hardware provider, excluding traditional analogue telephone services;.