Although big data can enhance financial decision-making in organisations (e.g., predicting financial performance), the epistemological argument of big data is that knowledge or truth which relies on (big) data needs to first be generated to make key decisions. Despite big data having the potential to enhance organisational decision-making, little empirical research has been conducted on the epistemology of big data driven financial decision-making. This paper uses knowledge management reliability (KMR) theory, as well as an interpretive strategy and expert interviews to contribute to the existing body of knowledge to understand the epistemological implications of decision-making with large data sets to predict financial performance in British banks. Our findings reveal a shift toward knowledge based data-driven decision making for predicting financial performance.