Success in upper-level accounting courses depends on adequate prerequisite knowledge because the learning process is sequential and hierarchical (Bentz 1975) and because prior learning provides cues for encoding and combining (Sternberg 1984). Building expertise requires a strengthening and organization of links between knowledge and not just a high volume of known facts (Dreyfus and Dreyfus 2005). Since incoming knowledge matters to later learning, this study investigated how enforcing the prerequisites impacted course outcomes in intermediate accounting. The prerequisites were enforced using a proficiency test administered online in a system that also offered tutoring to remedy any learning shortfalls. Students received all-or-nothing credit (100 percent or 0) for mastering adjusting entries and the financial statements. Students proficient in prerequisite skills earned better project and cumulative final exam scores in non-prerequisite areas. Grades in Intermediate II were also better after adding the proficiency test, compared to the two prior terms. The intrigue of these results goes beyond improved student outcomes in Intermediate I and II, because the testing and remedial instruction used an existing tutoring product, requiring no institutional resources or changes to course preparation, instruction, classwork, exams, or the project.