At the UMERC seminar we will present ongoing work in the project called "The dual role of process goals when implementing the written curriculum in Sweden and England". The project focuses on mathematical reasoning, for which we have so far analyzed how mathematical reasoning is described in different contexts, such as research frameworks, textbooks, and interviews with teachers. A purpose of the project is to explain how aspects of mathematical reasoning can be recontextualized via the curriculum chain, that is, from written policy document to implemented curriculum in the classroom. The project group consists of Ewa Bergqvist as project leader, Magnus Österholm, Lotta Vingsle, Lotta Wedman, Candia Morgan, and Jill Adler.