The COVID-19 pandemic is increasing older people's existing challenges in engaging with their physical and social worlds, and is thereby likely to worsen their loneliness. Digital technology has been offered as a potential aid for social connectedness during social distancing/isolation. However, many popular digital communication tools have not been designed to specifically address the needs of older adults impacted by social isolation. We propose that the social identity approach to health and the Social Identity Model of Identity Change (SIMIC) could be a foundation for digital interventions to address loneliness. While SIMIC applies to maintaining wellbeing during life transitions, it has not previously been rigorously applied to digital interventions. There are known challenges to integrating psychological theory to the design of digital technology, such as efficacy, user-autonomy, and engagement. The interdisciplinary field of Human Computer Interaction has a history of drawing on models originating from psychology to improve the design of digital technology and to design technologies in an appropriate manner. Drawing on key lessons from this literature, we consolidate design guidelines that could assist in applying SIMIC to digital interventions for loneliness in older people affected by the pandemic.