A rapidly growing body of research applies survey methods to examine the ability of SMEs to obtain external financing. These studies focus on firm-specific characteristics and demonstrate the impact of such ability on their own growth and overall economic growth, among other outcomes. However, the use of external financing is of crucial importance, especially whether SMEs can adopt innovation when they succeed in getting a loan. This paper reviews this literature that is not as extensive as the one focusing on typical investments with two purposes. First, we summarize recent work, providing a guide to its methodologies, datasets, and findings. Second, we consider applications of the literature in innovation, including insights for policymakers that seek to assess the potential economic effects of investments in innovation.