Several biases can occur when performing economic evaluations (EE) and it is important for researchers to minimize these biases, as they can significantly affect economic outcomes. This review aims, firstly, to identify biases that can occur in model-based EE and to illustrate their impact on economic outcomes and, secondly, to present a checklist for assessing the overall risk of bias in EE. Eleven biases that can occur in model-based studies were identified through a scoping review, scrutiny of systematic reviews, the authors' own experiences and discussions with experts. By combining these biases that can occur in model-based studies with biases that were identified for trial-based studies in a previous article, a 22-item checklist was developed for assessing bias in EE - the ECOBIAS checklist. This study and the ECOBIAS checklist aim to help researchers reduce biases in future EE, particularly in model-based EE. Nevertheless, further validation of the checklist is needed.
Keywords: bias; checklist; cost and outcomes; economic evaluation; model-based studies; systematic error.