When does BNG Apply?

Major Development

Biodiversity net gain became a mandatory requirement for major development submitted on or from the 12th February 2024.  

  • “Major development”means development involving any one or more of the following –the winning and working of minerals or the use of land for mineral-working deposits;
  • waste development;
  • the provision of dwellinghouses where—
    1. the number of dwellinghouses to be provided is 10 or more; or
    2. the development is to be carried out on a site having an area of 0.5 hectares or more and it is not known whether the development falls within sub-paragraph (c)(i);
  • the provision of a building or buildings where the floor space to be created by the development is 1,000 square metres or more; or
  • development carried out on a site having an area of 1 hectare or more

Small Sites

Biodiversity net gain for small sites, which do not fall into the category of major development will have an extended transition period and will apply from the 2nd April 2024.

"Small development" is defined as:

  • residential development where the number of dwellings is between 1 and 9, or if this is unknown, the site area is less than 0.5 hectares;
  • and commercial development where floor space created is less than 1,000 square metres or total site area is less than 1 hectare.
  • It is also development that is not for the winning and working of minerals; and/or waste management.


The following types of development are exempt from the BNG requirements:

  • Householder applications
  • Permitted development
  • Variations on existing planning permissions
  • Existing applications submitted prior to the 12th February or 2nd April 2024.
  • Applications subject to the 'de-minimis' threshold where the development does not impact a priority habitat, and impacts less than 25m2 of habitat that has a biodiversity value of greater than 0; and less than 5m of a linear habitat;
  • Biodiversity Gain Sites
  • Residential self build and custom-build applications

The full BNG exemptions are set out in The Biodiversity Gain Requirements (Exemptions) Regulations 2024; or DEFRA guidance