The economic justification of investments in information technology (IT) is a basic issue for IT management in private and in public‐sector organisations. Usually, the expenses made for any investment are compared to the cost saved. While the costs for implementing a new system are uncertain, only a small percentage of the benefits accrues as cost savings given the type of IT systems used today and the particularities of the public‐sector. In this paper, we present a methodology for the monetary quantification of the benefits resulting from the introduction of a modern IT application and demonstrate its use on the basis of a case of prison administration.