Biodiversity Net Gain (BNG)

Biodiversity Net Gain is a way of ensuring development has a measurable positive impact on biodiversity by comparing the biodiversity value of the site pre-development with the biodiversity value of the site post development.

The Environment Act November 2021 mandates the provision of 10% Biodiversity Net Gain (BNG) on the majority of development sites for 30 years.  This will come into force on 12 February 2024  and  will apply to outline, full and temporary applications.  From this date major development (unless otherwise exempt) will have to deliver net gains for biodiversity leading to positive outcomes for nature, better places for local communities and more consistent and transparent requirements for developers. Further information is available on the Defra website. The exempt developments are set out in the regulations.  Planning permission can now only be granted where a 10% gain is made as this is a mandatory requirement.

BNG for small sites came into force on 2 April 2024. The definition of small sites is summarised below. Small site development includes:

  • Residential development where the number of dwellings is between 1 and 9, or if unknown the site area is less than 0.5 hectares
  • Commercial development where floor space created is less than 1,000 square metres or the total site area is less than 1 hectare

The small sites metric and user guide can be found here.

Links to specific guidance are listed below. In addition the Future Homes Hub and the Planning Advisory Service (PAS) have launched ‘BNG Online’. This is a free digital resource offering practical guidance and advice on complying with BNG. It also directs users to a range of digital tools that can help to meet the requirements.



Defra Guidance and National Planning Practice Guidance (NPPG)

General Guidance

 Local Authority Guidance

 Developer Guidance

Statutory Biodiversity metric

 Onsite, Off-site provision and Biodiversity Gain Plan

Biodiversity Gains  Sites Register

Statutory Biodiversity Credits


 Land Manager Guidance 

Habitat Management and Monitoring Plan / Legal Agreements

 Kent Guidance

For specific information relating to Kent please visit the Kent Nature Partnership website , Kent County Council also has a page dedicated to Biodiversity Net Gain including guidance on the planning application process. Kent County Council has produced interim guidance including the approach to be taken in assessing the strategic significance of a habitat when completing the statutory metric.  This guidance will be replaced by the Local Nature Recovery Strategy (LNRS) which is due for completion 2025.  KCC has also produced a BNG site register which identifies potential, off site delivery sites.  Both can be found on the Making Space for Nature website.

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