This paper reports on a study on how Integrated Information Systems (IISs) support financial project management in a medium-sized consulting company. The study applies the case study method and the Constructive Research Approach (CRA). It was found that the Enterprise Resource Planning (ERP) system (an Online Transaction Processing (OLTP) system) primarily supports the task of data collection, while Microsoft Excel (an Online Analysis Processing (OLAP) system) can be used for reporting, budgeting and budget control. These two subsystems of the IIS are integrated with regard to ex post data stored in a common database. This allows access to real-time data throughout the IIS. However, some degree of disintegration exists as the project budgets are only stored in the spreadsheets, which presents a number of limitations with regard to reporting and analysis. The reason for using the combination of OLTP and OLAP systems is the need for flexibility and user-friendliness. Based on the findings, this paper expands the limited knowledge on how different kinds of systems support different management accounting tasks. The findings indicate that not only do OLTP systems support the management accounting of companies, but the user-friendliness and flexibility of OLAP systems also complement the OLTP systems in that respect.