The digitalization of Architecture, Engineering, & Construction (AEC), specifically the tunneling sector, often lags behind other sectors. Today's invoicing process of tunneling projects frequently involves many manual and paper-based tasks, which are error-prone and time-consuming. Accordingly, replacing this with a fully digital process, from the tunnel face to the project owner, bears high economic potential. This article proposes an integrated digital documentation system for tunnel construction management and invoicing. A month-long case study with data from a real-life construction site is conducted to test the system's suitability. The managed data are exported to commonly used enterprise resource planning (ERP) systems for invoicing and compared to actual invoicing data. The case study has shown that the proposed approach is practical and helped streamline and improve the construction documentation processes in conventional tunnel construction. The proposed solution represents an incremental contribution to the digital transformation of the AEC sector.