|| We have argued that cost accounting system should be modified in accordance with the purpose for using them and the context. Because no cost accounting system that is relevant in every business or environment exists. Relevant cost accounting system is determined in a particular
environment and context. This mode of thought relates directly to proposition which develops to explain the theory of 'cost accounting change'. This paper examines the relationships among the purpose, reflexibility and contexts of cost accounting system. The analysis based on reflexibility theory and some previous studies for activity-based costing and contingency theory indicated that: 1) Actual reflexibility about existing cost accounting was associated with two contextual variables: product diversity and process complexity. 2) A reflexibility required
mainly through the purpose for using cost accounting was associated with two contextual variables: competitive strategy and perceived environment uncertainty. Finally, we concluded that the relevance of cost accounting was lost and 'cost accounting change' became necessary when
the level of actual reflexibility didn't fit that of required reflexibility.