The Free Application for Federal Student Aid (FAFSA) is an important tool to help students find financial assistance. Not only do students fill out the FAFSA to apply for federal aid for post-secondary education, but also to be considered for aid by states, institutions, and private funders. Thus, filling out the FAFSA, specifically, and applying for financial aid, more generally, is one of many important steps that college-going students might undertake in their transition from secondary to postsecondary education (Klasik 2012), and challenges with financial aid considerations--alongside other barriers--may undercut students' access to higher education (Castleman and Page 2013, French and Oreopoulos 2017). This brief builds on prior National Center for Education Statistics (NCES) publications (Chen, Wu, and Tasoff 2010; Ifill 2016) to provide an updated and detailed look at why students or their parents reported that they did not complete the FAFSA. This report uses data from the 2013 Update of the NCES High School Longitudinal Study of 2009 (HSLS:09), a nationally representative study of a cohort of students who were ninth-graders in fall 2009. HSLS:09 focuses on understanding students' trajectories from the beginning of high school into higher education and the workforce.