This presentation takes its departure in the new curriculum for Swedish preschool where preschool teacher’s responsibility for teaching subject matters such as mathematics, has been strengthened. The teaching is recommended to have a thematic approach, to be play-based, and intertwine care, development, and learning. Also, the curriculum states that teaching can be both planned and spontaneous. The task given by the government is complex and calls for a problematization of teaching planning and what role planning can have in preschool especially for mathematics teaching. The ongoing study aims to investigate teaching planning and how preschool teacher and child minders prepare and change their mathematics teaching during the time of planning.