Successful application of the mitigation hierarchy requires biodiversity assessments and spatial planning to inform the design of mitigation policies, identify priority areas for biodiversity conservation and impact avoidance, assess the biodiversity impacts of developments, and identify appropriate mitigation measures including offsetting residual impacts. Guidance on the necessary biodiversity data and assessment techniques is often lacking, especially in countries where formal mitigation policies do not exist or are in their infancy. In this open-access paper in Conservation Science and Practice, several COMBO team members and others demonstrate analyses that can help answer some key questions for formulating effective mitigation policies and applying the mitigation hierarchy. We focus on data and analyses that can inform the avoidance and offset steps in particular, and demonstrate these techniques using a case study in Mozambique.