This critical review introduces a template that links phosphorus (P) sources and mobilisation processes to the delivery of P to receiving waters where deleterious impact is of concern. It therefore serves as a key introductory paper in this special issue. The entire process is described in terms of a ‘P transfer continuum’ to emphasise the interdisciplinary and inter-scale nature of the problem. Most knowledge to date is derived from mechanistic studies on the sources and mobilisation of P using controlled experiments that have formed the basis for mitigation strategies aimed at minimising transfer from agricultural fields. However, our ability to extrapolate this information to larger scales is limited by a poor knowledge base while new conceptual advances in the areas of complex systems and fractal dynamics indicate the limitations of past theoretical frameworks. This is compounded by the conceptual and physical separation of scientists working at different scales within the terrestrial and aquatic sciences. Multi-scaled approaches are urgently required to integrate different disciplines and provide a platform to develop mechanistic modelling frameworks, collect new data and identify critical research questions.