How different public agencies and their digital artifacts work together (often labeled as interoperability) is considered to be an important area for a successful evolution of e-government. Key knowledge in this area is the structuring into four different layers of interoperability: legal, organizational, semantic, and technical interoperability. This paper challenges this received view of digital interoperation. It does so through an in-depth qualitative case study on the management of digital medical certificates and an inductive and abductive data analysis. Twelve aspects of digital interoperation have emerged through this study. The aspects have been divided into two categories: intrinsic (aspects that directly relate to the digital transfer of information) and extrinsic (aspects that shape different parts of digital interoperation from the outside). Six intrinsic aspects have been identified (relational, performative, semantic, informational, architectural, and technical). These intrinsic categories also have roles as extrinsic. Besides these, there are six more extrinsic aspects (normative, regulative, economic, cognitive, interactive, and temporal). Based on empirical insights and theorizing, the paper argues for a broadening of interoperability as not only the capability to interoperate. A broader notion comprises a mix of organizational, human, and digital pre-conditions for interoperation.