The introduction of a complex system, such as an Enterprise Resource Planning (ERP) system, requires users to adapt to the simultaneous requirements of the new system and the associated organisational and business process changes. Unsuccessful adaptation to complex mandatory systems generates significant financial and opportunity costs to organisations and makes some employees feel dissatisfied with their jobs. Previous information systems (IS) research provides important insight into IS use. However, there is a lack of an in-depth study of the process of user adaptation that explains how user adaptation behaviours change over time and what triggers users to modify their system use behaviours. This study unveils the dynamic adaptation process and offers an explanation of how adaptation behaviours unfold over time.

The fieldwork was conducted in four organisations in Thailand: one private, one state-owned, one non-profit and one multinational. An embedded multiple-case study design was applied in this research. Using the critical incident technique, 46 in-depth interviews were conducted with ERP users, managers and IT specialists. Grounded theory informed both the method of data analysis and the technique for theory building. As a result of an inductive theorising process, three intertwined core themes emerged. The first theme, user adaptation behaviours, reflects the different ways in which users respond to the evolving work practices that an ERP system imposes. The second theme, situational conditions, reveals the underlying conditions that influence the user adaptation process including social-task-user conditions and system-business process comprehension. The third theme, triggers, refers to events that change user perceptions towards the system or changes in the work environment.

This study produces an emergent, substantive theory that explains how individuals dynamically adapt to complex mandatory IS. These adaptation behaviours, which are shaped by situational conditions, manifest in the form of reluctant, compliance, faithful and enthusiastic adaptation behaviours. Through their interaction with the system, individuals are constantly assessing the system in relation to the existing situational conditions. The adaptation behaviours espoused at any given time can be subsequently modified through task-related, organisational-related and system-related triggers.