If non-completion rate is to be a useful performance indicator it must reflect the recent health of a course in a transparent and robust manner that enables comparisons to be made between groups of students and between courses of varied structures. For flexible degree programmes with varied attendance modes and multiple entry points, traditional non-completion rates based on entry cohorts of students starting in the same academic year do not generally provide useful information, because the cohorts rapidly fragment. Synthetic cohort methods using data from all years of a course to simulate the behaviour of a fictional entry cohort are useful at institutional level but are difficult to implement at course level. A non-completion performance indicator, which uses exit cohorts of students leaving the course in the same academic year, is a simple and robust measure that gives good comparative statistics for both straightforward and complex degree programmes. (Contains 2 tables and 2 figures.)