(With acknowledgement to the contribution of Simon Taylor) A number of papers have been published describing various System Dynamics [SD] models of the Information Systems Investment Appraisal [ISIA] process from several academic and professional viewpoints. This paper builds on previous papers by the author and others that have produced a taxonomy of SD Models of the ISIA process. This paper adds to the taxonomy by describing a study that produced a simplified System Dynamics Model of an intervention based on an Enterprise Resource Planning [ERP] application and designed to produce a transformation of certain IS business processes in a professional services company. This acts as an exemplar of one of the model types described in the taxonomy – the “Business Value of Process Change” type and compares “before and after” the intervention models. You are welcome to discuss your ideas and contributions to any aspect of the evolution of SD Models of Information Systems Investment Appraisal at this session!