In South Africa, citizens in both low- and high-income areas are increasingly providing their own services to mitigate the unreliability, unaffordability and inaccessibility of state services. This article examines diverse case studies across socio-economic and residential typologies to explore shifts in service provision responsibilities from the state to the citizen. Applying an interdisciplinary approach, this article considers the political impacts of these strategies, arguing that the ways in which citizens supplement and substitute for the state contests and (re)negotiates spaces of sovereignty. While urban studies overwhelmingly analyse these actions through the lens of informality, we argue that sovereignty (the supreme authority of a state to govern itself without external interference) offers a less binary analytical lens. State substitution is increasingly a daily act for many, not only in low-income settlements but also among elites. The article further examines state responses to citizen-led actions in supplementing or substituting services, demonstrating how they range from inaction to permissive negotiation and, rarely, repression. Thus, the political impact of service substitution requires deeper reflection, raising questions regarding the nature of the state and the social contract.