The global digital shift, recently accelerated by the COVID‐19 pandemic, requires that consumers have knowledge allowing them to navigate increasingly cashless markets safely and effectively. To enable valid and reliable measurement of such knowledge, we used data obtained from a random sample of adult Poles to develop and evaluate the psychometric properties and applicability of an original cashless payments knowledge scale (CPK scale). Our analyses based on Item Response Theory show that some evident subdomains exist within the CPK construct. The separate dimensions of the CPK merge into a coherent scale with solid psychometric properties. We find that the CPK score depends on the place of residence, education, and household size, and is positively related to safe cashless behavior. Our findings may have important implications for financial institutions as well as policymakers interested in segmenting consumers in terms of their financial knowledge, potential risks resulting from deficits in this knowledge, and enhancing financial literacy.