Biodiversity Net Gain

Application requirements and guidance. Biodiversity statement template.

Biodiversity Net Gain (BNG) is a way of creating and improving natural habitats through the planning process.

Biodiversity net gain is needed, as one of many actions, to address the significant and troubling losses in biodiversity and bio-abundance. Further evidence is available in the UK State of Nature Report on the Natural England website (external link) and in the State of Surrey’s Nature publication on the Surrey Wildlife Trust website (external link).  

Under the Environment Act 2021, development must achieve at least a 10% net gain in biodiversity value, compared to the pre-development baseline, unless the development is exempt. A standardised calculation tool is used, known as the biodiversity metric, to ensure consistency and transparency. The number of biodiversity units is based on area of the habitat, its distinctiveness and its condition. Please note that a post-development private garden is discounted because it has no public access and biodiversity net gains cannot be legally secured.

If it is not possible to meet all or part of your BNG units 'on site' and you need to purchase ‘off site’ units, you may find the following unit finder websites of use. Please note that these websites have not been verified or endorsed by the Council and other sources may be available.

Future Homes Hub UK (external link)

Gaia - BNG Marketplace (external link)

Local Biodiversity Units Available - Habitat Bank Network (external link)

BNG Finder - Find and Sell Biodiversity Units (external link) 

For national information and guidance about BNG, see the full collection of Biodiversity Net Gain webpages on the GOV.UK website (external link).

From the 6 August 2026 the government amended the type of development exempt from BNG. The self-build or custom build exemption no longer applies for new applications.    

Council requirements

To support your application the Council’s Biodiversity Statement template, link below, is required to be completed and submitted (this is a local validation requirement).