Longitudinal Education Outcomes (LEO) data provides information on how much UK graduates of different courses at different universities are earning, either one, three or five years since graduating. This briefing gives an overview of what LEO data is and how it can be useful to students, policy makers and higher education institutions. It also explores the limits to using LEO data, focusing on the reasons why it should not be used as an instrument for driving funding decisions (either funding directly from government or access to student loan funding).