Biodiversity offsets aim to provide a measurable biodiversity benefit, or gain, to compensate for impacts, or losses, from development activities. A key challenge of biodiversity offsetting is that relevant information is often difficult to obtain, or in many cases, may not exist. An increasingly common technique for addressing conservation knowledge gaps, particularly with limited resources to collect empirical data and the short time frames associated with decision making, is the use of expert knowledge. Currently, there are no guidelines available on how to apply structured expert elicitation in a biodiversity offset context. This document provides step-by-step guidance on how to use expert elicitation to estimate the benefits and costs of a range of biodiversity offset actions.