Company transactions are increasing in number and value and is a method used for external growth. The increase in mergers and acquisitions can mainly be seen during the last decades and is now a common strategy on both a national and international level. However, most transactions experience problems with fulfilling the perceived value and synergies. Furthermore, digitalisation has created a higher dependency of companies on various IT systems, and rapid technological advancement has made the processes and theories regarding IT integration outdated. Thus, there is limited research on the relationship between IT systems and company integration and integration performance. The study aims to explore IT systems integration in the context of company transactions as well as attempts to identify key factors that influence integration performance. To explore the field, an embedded multiple-case study was conducted with a company performing international company transactions. The empirical study can be divided into three parts. First, initial interviews to probe the subject and gather information to create a holistic view of the problem. Second, gathering qualitative and quantitative data on the cases and conducting in-depth interviews. Third, the main study and exploration of the cases and collected data. Additionally, a literature review was conducted to create the theoretical foundation for the analysis and to complement the primary data.

The thesis found that an objective method to measure performance is needed since the general view of the integration is not necessarily representative of the actual performance. The factors that influence performance were identified as of both strategic and organisational nature, where strategy and processes are important early on to create a common view of the project. People change management and active involvement from both parties are essential during the integration.

The thesis contributes to the research field by exploration of the gap between theories regarding mergers and IT integration as well as by suggesting a nuanced view of the current approach to strategic alignment. Furthermore, the study builds on the general theory of measurement of integration performance by suggesting a metric to measure the performance of IT integration projects.