An illustrative excel model to demonstrate how NPV neutral true-ups could be calculated in practice. This relates to our proposal to transition from RPI to CPI (or CPIH) from 2020. The true-up model is pre-populated with industry data which users may adjust. While assumptions have been inserted on the speed of transition in future regulatory price control periods, the assumptions are illustrative and should not be interpreted as Ofwat policy. This model is an XLSB format spreadsheet.