Verification and validation are essential aspects of mathematics and beyond in STEM, but these constructs are not consistently defined in research nor in curricula documents. In this theoretical paper, we argue that verification and validation are largely characterized as binary judgments by teachers and researchers about what students do. We then present empirical examples of student work to show this view does not account for students' thinking as they resolve problems. We conclude that in order to foster learners who are confident and capable in STEM fields, it is necessary to revisit how verifying and validating activities are conceptualised and developed across years of schooling.