Governments aim to digitalize public services. Whereas initially they worked in isolation, nowadays they increasingly link different building blocks together to realize integrated public services. This evolution poses challenges concerning the governance of public services. The purpose of this paper is to identify governance challenges in inter-organizational digital public service delivery. To do this, we investigated a case study that deals with the creation of digital invoicing services in Belgium. The findings show seven groups of governance challenges that incorporate technical, organizational and inter-organizational factors. Governance challenges can be external, related to the environment and the users, as well as internal, related to the digitalization objectives and governance dynamics. Moreover, as public services evolve over time, so do governance challenges, suggesting that governance regimes may have to evolve accordingly to maintain coordinated service delivery.