The first step in activity-based costing involves identifying activities and classifying them according to the cost hierarchy. Cost hierarchy is a framework that classifies activities based the ease at which they are traceable to a product. The levels are (a) unit level, (b) batch level, (c) product level, and (d) facility level.
Unit level activities are activities that are performed on each unit of product. Batch level activities are activities that are performed whenever a batch of the product is produced. Product level activities are activities that are carried out separately for each product. Facility level activities are activities that are carried out at the plant level. The unit-level activities are most easily traceable to products while facility-level activities are least traceable.