The Biodiversity Net Gain approach is a commitment to promote biodiversity net gain (i.e. leaving biodiversity in a better state than before) across the Manchester City Region in the United Kingdom. This approach forms part of the Five Year Environment Plan for Greater Manchester (2019-2024). The instrument - which is anticipated to become mandatory through the forthcoming Environment Act in 2023 - requires all developments under the Town and Country Planning Act to achieve a net gain for biodiversity of 10%. The approach is underpinned by a set of good practice principles whose compliance must be explained as part of a planning application to ensure that the plans are robust and foster Biodiversity Net Gain. In addition, five sequential phases are proposed to show how net gains in biodiversity can be integrated into the development and assessment process. A system of ‘biodiversity units’ is used to measure biodiversity before and after site development.