Abstract: The invention relates to a system and method for registering and certifying activity and/or communication between terminals, of the type in which a registry and certification service provider registers the telematic content exchanged between a user and a service provider during a transaction using a registry and certification server and issues an electronic certification upon completion of the service. According to the invention, the registry and certification server is connected to an official time server in order to obtain reliable time stamps and to a client capture module which is installed in the user terminal in order to register periodic captures of the interface of the user terminal and data relating to the connections established thereby and to include same in the electronic certification document together with the reliable time stamps. The electronic certification document is authenticated using an electronic signature provided by the registry and certification service provider.