This paper reports a case study of budgeting at an Australian university to understand how accounting is involved in processes of legitimation. The university had been much enlarged and diversified in its educational offerings through a series of mergers. A response to the changes on the part of the vice-chancellor was to introduce a new budget system borrowed from the institutional environment. The intent was to convey to a key funding agency and to staff that the newly merged entity would be governed appropriately. We analyze a set of sequential and interlinked processes in which these aspirations were challenged repeatedly by senior academic and administrative staff. Finding the budget system to be inconsistent with their values and expectations for the university, staff undermined it through patterns of under- and over-spending. We show how these behaviors jeopardized the vice-chancellor's efforts to legitimate the organization's financial management practices for a key funding agency. A core contribution of our paper is to analyze empirically the importance of the institutional demands that an organization's internal constituents may make of its accounting practices. We argue that managers, staff and other internal constituents should be seen as significant legitimating agents. We show how attention to their demands becomes all the more relevant when budget and accounting systems for internal use are loosely coupled from those used for external reporting. In such circumstances, conflicting demands by internal and external constituents may not be dealt with through the development of separate and compartmentalized systems. This makes it problematic to assume that adoption of accounting systems from an institutional field will result in a steady-state of organizational legitimacy.