The problem of designing and developing information system applications is like sitting on the fence because the knowledge of two very different domains must be aligned, i.e. the business domain the application refers to and the information system engineering domain responsible for the application’s design and development. In this article ‘activity-based cost & GHG accounting’ is selected due to its recent appearance for solving the design and development problem by establishing a ‘real-time add-on’ digital GHG accounting information system (GHG-AIS) application with the ‘object-oriented’ domain engineering methodology. The ‘real-time’ capability is the key feature of the digital AIS application that distinguishes it from a ‘manual’ – e.g. spreadsheet – application, and the ‘add-on’ feature assures compatibility to the production information systems incorporated in existing ERP systems.