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
BNG rules do not apply to the following types of development.
Planning applications submitted before mandatory BNG
Any planning applications for developments made before 12 February 2024 are exempt from BNG.
Small developments
Any planning applications for small (‘minor’) developments made before 2 April 2024 are exempt from BNG.
Read what constitutes a small development.
Variations of planning permission
Transitional arrangements also apply for variations to existing planning permissions. For example, where the original planning permission was not in scope of BNG, BNG will not apply to future variations in most cases.
There is more information in the planning practice guidance.
Householder applications
These are small projects householders carry out in their own homes. They can include:
- home extensions
- conservatories
- loft conversions
These applications are defined within article 2(1) of the Town and Country Planning (Development Management Procedure) (England) Order 2015.
Developments of 0.2 hectares or below
From 6 August 2026, BNG does not apply to planning applications for developments where the site area within the red line boundary is 0.2 hectares or below.
Developments subject to the ‘de minimis’ rule
BNG does not apply to developments that impact less than:
- 25 square metres (5m by 5m) of on-site habitat within the red line boundary
- 5 metres of on-site linear habitats such as hedgerows
This rule is called the ‘de minimis’ exemption.
Temporary developments
From 6 August 2026, BNG does not apply to short-term developments if:
- the whole development is temporary
- planning permission is granted for 5 years or less
If there is an impact on priority habitat on-site, the exemptions for the following developments do not apply and BNG must be met:
- developments of 0.2 hectares or below
- developments subject to the ‘de minimis’ rule
- temporary developments
A development ‘impacts’ a habitat if it decreases its biodiversity value.
Self-build and custom build applications
The self-build or custom build exemption will no longer apply for new planning applications after 6 August 2026.
Your self-build or custom build is exempt from BNG if you apply for:
- planning permission before 6 August 2026
- a variation of planning permission on or after 6 August 2026, and the original planning permission was exempt
You must also meet all of the following conditions to qualify for an exemption as a self-build or custom build. It must:
- consist of no more than 9 dwellings
- be on a site that has an area no larger than 0.5 hectares
- consist exclusively of dwellings that are self-build or custom housebuilding as defined in section 1(A1) of the Self-build and Custom Housebuilding Act 2015
Find out more about what qualifies as self-build and custom housebuilding.
Sites created for off-site BNG gains
Developments creating or enhancing habitats solely or mainly for the purpose of fulfilling the BNG planning condition for another development are exempt.
This is because these gain sites are created to offset the BNG for another development.
High speed rail transport network
An exemption applies to developments that are part of, or ancillary to, the high-speed railway transport network. This includes connections between all, or parts of the places listed 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)
Further information
There is more guidance from Ministry of Housing, Communities and Local Government (MHCLG), including on:
- variations of planning permission
- the ’de minimis’ exemption – including what evidence you may need to submit to show this exemption applies
- temporary development exemption
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Updates to this page
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Clarified that any existing planning applications made before 12 February 2024 are exempt from biodiversity net gain (BNG), including small developments. Clarified that for variations of planning permission, where the original planning permission was not in scope of BNG, mandatory BNG will not apply to future variations. Clarified the exemption for developments subject to the ‘de minimis’ rule. Added a link to the list of priority habitats and species in England. Self-build and custom build applications made after 6 August 2026 are no longer exempt from BNG rules. The new exemption for planning applications for developments of 0.2 hectares or below and temporary developments is in place from 6 August 2026.
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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.
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Removed 'small developments' from the exemptions list as small developments are subject to BNG from 2 April 2024.
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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.
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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.
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First published.