This paper studies the decentralization aspects as far as use of Management Accounting Systems (MAS) “operational approach” is concerned. Not only in the Sultanate of Oman but also in India and in many developed and developing countries I have observed that Management Accounting System(s) is used in a conventional format and not in open access format. This conventional format approach is mainly an approach of centralized management accounting system. Specifically speaking, almost all financial institutions either are or has to be customer-oriented. Without customer we can only dream of doing business. By customer orientation I mean creating new and/or increasing number of customers via customers through “effective marketing”, increased “customer facilitation”, increased “support services” etc. This can be achieved through decentralization and open-access system of conventional management accounting system(s) with the initiatives and programs of customer-orientation. This paper explores and shows the relationship between decentralization and open-access of conventional management accounting system(s) with the initiatives and programs of customer-orientation (i.e. effective marketing, increased customer facilitation and support, etc.). In its totality, the paper suggests that current operational approach of centralized management accounting systems used in financial institutions in developed / developing countries and/or in many countries are not in accordance to the ambitions of increased customer-orientation, and therefore, to obtain such orientation, these systems are in need of decentralization which will allow all calculations, statistics, and other processed data that can be viewed by customer-intensive divisions like marketing, sales, customer support, human resource etc. as well for better results and help in creating more benefits for all concerned parties.