The aim of this project was to examine the effectiveness of feedback offered by computer-aided assessment (CAA). CAA provides practice tests for undergraduates, and feedback to help them improve their scores and mathematical understanding. However, there is a lack of evidence-based literature on the effect of formative feedback in mathematics learning (Crockett et al. 2009), and so a desire for research to examine the effectiveness of the feedback that CAA provides (Sangwin 2007). The authors refer to Ramaprasad (1983), Taras (2002) and Yorke (2003) when defining formative feedback to comprise: (1) a judgement made against a given standard; (2) advice for the student to close the gap between current performance and this standard; and (3) evidence to demonstrate an improvement has been made. Mathematics undergraduates working with CAA at Loughborough University may access practice tests multiple times for a limited period usually a week prior to a summative testing period. The questions in the practice tests are similar to those in the following summative test. The CAA system marks each attempt, and returns a score with feedback for each question. Feedback usually comprises full worked solutions. Research questions include: (1) Are students able to identify learning gaps by using CAA?; (2) Are students given the advice they require to reduce these learning gaps?; and (3) Can students demonstrate an improvement with respect to these learning gaps? Focus groups enabled the authors to seek the opinions of students directly, and to pursue the points they raised in more detail. This permitted the authors to capture the issues for a few cases, and the authors sought to investigate the generalisability of their conclusions with questionnaires. The sample was taken from a class of 237 registered students. The students in this group believed CAA helped them to identify learning gaps.