The Independent Pricing and Regulatory Tribunal determines maximum fares for rural and regional bus services. In making decisions on appropriate fare changes for these services we consider the change in costs faced by the industry over the past year. We do this using the Bus Industry Cost Index (BICI). The BICI model is now available from our website as an Excel file (www.ipart.nsw.gov.au). This paper is a guide to the Excel file. It provides some background on how cost indices work and then steps users through the Excel file. We recommend that this paper is read in conjunction with the Excel file.