Distribution networks have traditionally had low levels of automation and control, primarily centered around the use of SCADA to monitor medium voltage (MV) feeders together with a lower usage of distribution management, voltage control, and automatic reconfiguration systems. However, the connection of large numbers of distributed energy resources (DER) has given rise to the need for greater monitoring and control, with more advanced control systems being seen as a method of managing the impact of DER on system frequency and voltage and enabling a more coordinated interface between transmission system operators (TSOs) and distribution system operators (DSOs). The reasons for needing an interface between TSOs and DSOs can be grouped into three main areas: market framework, operational interaction, and planning interaction. Increasing levels of interaction will be needed to manage the impact of DER on frequency, reactive power, voltage, and resiliency. New functionality will need to be developed to give greater observability of networks to both TSOs and DSOs and to allow greater control of DER through dynamic operating envelopes and emergency backstop mechanisms. Distribution state estimation helps give greater visibility of the state of the network, and autonomous control built into DER will play an important role in managing local voltage. The social aspects of TSOs and DSOs controlling consumers’ DER need to be considered.