Developing and communicating fraud prevention policies is the most effective way to reduce potential losses due to ongoing expense fraud because it creates a culture of integrity and accountability, sets clear expectations and consequences for employees, and deters fraudulent behavior. Implementing user access controls, performing regular internal audits, and conducting fraud prevention awareness training are also important controls, but they are more reactive and detective than preventive. References = Risk and Information Systems Control Study Manual, Chapter 4, Section 4.3.2, page 4-26.