It is widely accepted that mathematical competence is of great importance whenlearning physics. This paper focuses on one aspects of mathematical competence,namely mathematical reasoning, and how this competency influences students’ successin physics. Mathematical reasoning required to solve tasks in physics tests, within anational tests system, is separated in imitative and creative mathematical reasoning.The result shows that students lacking the ability to reason mathematically creativelyare more likely not to do well on national physics test, thus not fully mastering thephysics curricula. It is further discussed how the high demands of creativemathematical reasoning in physics tests stand in contrast to what is known about theeducational practices in mathematics and physics in upper secondary school