Guidance

Biodiversity net gain: exempt developments

A guide to the types of development that will be exempt from the mandatory biodiversity net gain (BNG) requirements.

Applies to England

Biodiversity net gain (BNG) is mandatory from 12 February 2024.

You can view all of the BNG guidance in the BNG collection.

The developments listed in this guide are exempt from BNG rules.

Existing planning applications 

If a planning application for a development was made before day one of mandatory BNG on 12 February 2024, the development is exempt from BNG.

Variations of planning permission

Transitional arrangements also apply for variations to existing planning permissions. There is more information in the planning practice guidance.

Developments below the threshold

A development that does not impact a priority habitat and impacts less than:   

  • 25 square metres (5m by 5m) of on-site habitat   
  • 5 metres of on-site linear habitats such as hedgerows

A development ‘impacts’ a habitat if it decreases the biodiversity value.   

Find out more about this exemption.

Householder applications

These are applications made by householders as defined within article 2(1) of the Town and Country Planning (Development Management Procedure) (England) Order 2015.

It includes, for example, small projects like home extensions, conservatories or loft conversions.

Self-build and custom build applications

You must meet all of the following conditions to qualify for an exemption as a self-build or custom build.

The development must:  

Find out more about what qualifies as self-build and custom housebuilding.

Biodiversity gain site

Developments undertaken mainly for the purpose of fulfilling the BNG planning condition for another development are exempt.

High speed rail transport network

An exemption applies to any development forming part of, or ancillary to, the high-speed railway transport network, comprising connections between all or any of the places or parts of the transport network specified in section 1(2) of the High Speed Rail (Preparation) Act 2013.

Other exemptions

The following are exempt by the Environment Act 2021:

  • urgent crown developments 
  • developments that are granted planning permission by a development order (including permitted development rights)

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Updates to this page

Published 29 November 2023
Last updated 21 August 2024 + show all updates
  1. Updated to add clarity about what criteria a development must meet to qualify for exemption as a self-build or custom build. A link has been added to guidance on self-build and custom housebuilding.

  2. Removed 'small developments' from the exemptions list as small developments are subject to BNG from 2 April 2024.

  3. Updated box at top of page to state that biodiversity net gain (BNG) is mandatory from 12 February 2024 and removed the 'draft guidance' label. Also provided more clarity around the 'Developments below the threshold' exemption. Added other exemptions.

  4. Updated to clarify that a small site does not fall into the category of a major development, as defined in article 2(1) of the Town and Country Planning (Development Management Procedure) (England) Order 2015.

  5. First published.

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