This paper focuses on one aspect of mathematical competence, namelymathematical reasoning, and how this competency influences students’ knowing ofphysics. This influence was studied by analysing the mathematical reasoning requirementsupper secondary students meet when solving tasks in national physics tests.National tests are constructed to mirror the goals stated in the curricula, and these goalsare similar across national borders. The framework used for characterising the mathematicalreasoning required to solve the tasks in the national physics tests distinguishesbetween imitative and creative mathematical reasoning. The analysis process consistedof structured comparisons between representative student solutions and the students’educational history. Of the 209 analysed tasks, 3/4 required mathematical reasoning inorder to be solved. Creative mathematical reasoning, which, in particular, involvesreasoning based on intrinsic properties, was required for 1/3 of the tasks. The results inthis paper give strong evidence that creative mathematical reasoning is required toachieve higher grades on the tests. It is also confirmed that mathematical reasoning isan important and integral part of the physics curricula; and, it is suggested that theability to use creative mathematical reasoning is necessary to fully master the curricula