This report highlights the need teachers of mathematics have to build on their knowledge about mathematics and how to teach it throughout the different stages of their career. The diversity of professional learning provision and competing demands on teachers and senior leaders mean that it can be difficult to know how to prioritise mathematics-specific professional learning. There is also no mathematics-specific professional learning guidance to guide these choices. To help fill this gap, an expert panel was created to develop principles on professional learning for teachers of mathematics, bringing together expertise from the classroom, from research and professional learning.