With pending revisions to NRCS nutrient management standards, there is increasing interest in the use of models to augment measured phosphorus loss data in the validation and improvement of P Indices.  Here we present an overview of recent and proposed developments within the SWAT model, including revised soil and instream phosphorus routines.  We also examine recent comparisons of model predictions and measured data, and discuss the relative importance of phosphorus loss predictions in the context of real world uncertainty.