In order to better understand what Controlling module is, have a look at what it is not;
CO is not just costs.Many people mistakenly think that CO stands for cost management. While the controlling module does support cost management, it certainly is not limited to cost management. Much of the profitability reporting resides in the CO module.
CO is not focused on transaction or business process automation. The other modules of the R/3 system primarily focus on the automation and execution of business processes and transactional postings for data capturing and tracking. The CO module is focused more on aggregate information with the added benefit of having drill-down capability to the actual transactional postings, providing a very robust audit trail.
CO is not configuration based. Many CO implementations mistakenly design, manage, test, and implement the CO module like the other SAP R/3 modules, focusing on configuration as an indication of complexity. To estimate resource and time requirements, most projects use the number of configuration scripts. However, this heuristic in the CO module leads to understaffed CO engagements. The CO module is business decision oriented, not transaction focused. Its implementation parameters are more appropriately driven by the complexity of information and analysis rather than being configuration driven. Defining the conceptual design, the complete organizational costing model, drives the CO implementation. Time and expenses for a CO module implementation are driven by the master data, drivers, allocation methodologies and complexities, number of profit dimensions, cost objects, and events. It is not uncommon for the CO module implementation to require more analysis/design and less testing/construction time than other modules.