Corporate fraud these days represents a huge cost to our economy. In the paper we address one specific type of corporate fraud, internal transaction fraud. Given the omnipresence of stored history logs, the field of process mining rises as an adequate answer to mitigating internal transaction fraud. Process mining diagnoses processes by mining event logs. This way we can expose opportunities to commit fraud in the followed process. In this paper we report on an application of process mining at a case company. The procurement process was selected as example for internal transaction fraud mitigation. The results confirm the contribution process mining can provide to business practice.