We first examine whether audit fees decrease when European real estate firms switch from amortized cost to fair value. Specifically, we use mandatory adoption of IAS 40 in Europe as a natural experiment to conduct a difference-in-differences analysis. We compare how audit fees change upon mandatory IFRS adoption for two sets of European real estate firms: those domiciled in countries requiring that property assets be reported at amortized cost under pre-IFRS domestic standards (treatment group), and those requiring that property assets be reported at fair value under pre-IFRS domestic standards or early IFRS adoption (control group). If audit fees vary with the firms’ primary reporting model (H1A), we should find a significantly larger change in audit fees for the treatment group (which transitions from a cost-based model to a fair value-based model) compared to the control group (which remains on a fair value-based model throughout the analysis period).