The soft scalar mass β-function

We present an exact formula for the β-function for the soft-breaking scalar mass in an N=1 supersymmetric gauge theory, in the form of an operator acting on the anomalous dimension. In particular we give the exact form for the correction due to the ϵ-scalar mass, and show that it has a particularly simple form in the renormalisation scheme corresponding to the exact NSVZ gauge β-function.