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 and custom build exemption no longer applies for new planning applications made on or after 6 August 2026.
Your self-build or custom build is exempt from BNG if you applied 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
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