This review identifies successful approaches to collating and using biodiversity data in spatial planning and impact assessment, the barriers to obtaining and using existing data sources, and the key data gaps that hinder effective implementation. The analysis is a contribution to the EU BON project funded by the European Commission FP7 research programme, which aimed to identify and pilot new approaches to overcome gaps in biodiversity data in conservation policy at European and national levels. The consideration of biodiversity in impact assessments and spatial planning requires spatially explicit biodiversity data of various types. Where spatial plans take account of biodiversity, there are opportunities through Strategic Environmental Assessment (SEA) of development plans and Environmental Impact Assessment (EIA) of individual development proposals to ensure that consented activities are consistent with no net loss of biodiversity or even a net gain, and help to maintain or develop coherent ecological networks. However, biodiversity components of SEAs and EIAs have often been found to be of insufficient quality due to the lack of data or the inadequate use of existing data. Key obstacles to providing access to biodiversity data include the need for data standardisation and data quality governance and systems, licensing approaches to increase data access, and lack of resources to target gaps in data coverage and to develop and advertise policy-relevant data products. Existing data platforms differ in the degree to which they successfully provide a service to spatial planners and impact assessment practitioners. Some local governments, for example Somerset County Council in the UK and the Bremen federal state in Germany, have invested in integrated data collection and management systems that now provide intensively used tools for spatial planning and impact assessment informed by local data collection and monitoring. The EU BON biodiversity data portal aims to provide a platform that is an access point to datasets relevant to essential biodiversity variables on species, habitats and ecosystems. The EU BON taxonomic backbone provides an integrated search function for species and taxa according to different classifications, and also provides a range of tools for data analysis and decision-support. This will increase the accessibility of the vast range of biodiversity data available in different sources and allow the targeting of future data collection to address current gaps.