The objective of the contract is to stabilize and optimize the existing IT-systems at DGI funded by GIZ, by name ATOM, GovIn/TAS Gov, FUSION and the Control Module, in a way that by the end of the contract these systems can be operated by DGI independently from external funding. To achieve this, the contractor is responsible for providing the following work packages and for realizing the corresponding milestones: - Improving the usability of ATOM, GovIn/TAS Gov, FUSION and Cerbère - Promoting the institution wide appropriation of ATOM, GovIn/TAS Gov, FUSION and Cerbère by tax administration agents and taxpayers - Accompanying the handover of ATOM, GovIn/TAS Gov, FUSION and Cerbère