The Government is changing some of the statutory biodiversity net gain requirements from 6 August 2026.
Biodiversity net gain, usually referred to as BNG, requires most development to deliver at least a 10% increase in biodiversity value unless an exemption applies.
The changes apply to planning applications made on or after 6 August 2026. Applications made before this date will continue to be considered under the previous BNG requirements.
What is changing?
 1. New exemption for sites of 0.2 hectares or less
Development will be exempt from mandatory BNG where the area within the planning application red line boundary is no more than 0.2 hectares.
This exemption will not apply where the development would negatively affect an onsite priority habitat.
2. New exemption for temporary development
Development may be exempt where the whole development is temporary and planning permission is granted for a period of five years or less.
The permission must require the development to be removed and the land reinstated within that period.
This exemption will not apply where the development would negatively affect an onsite priority habitat.
3. Removal of the self build and custom build exemption
The separate exemption for self build and custom build housing will no longer apply to planning applications made on or after 6 August 2026.
A self build or custom build proposal may still qualify for another exemption, including the new exemption for sites of 0.2 hectares or less.
4. More flexibility for minor development
Minor development that remains subject to BNG will have more flexibility over how the required biodiversity gain is provided.
Onsite habitat creation or enhancement and registered offsite biodiversity gains can be considered at the same stage. Applicants will no longer have to demonstrate that onsite delivery has been considered before using registered offsite gains.
The purchase of statutory biodiversity credits will remain the final option.
Applications submitted before 6 August 2026
The changes are not retrospective.
Planning applications received by the Council before 6 August 2026 will continue to be considered under the BNG requirements that applied when the application was received. This applies even where the application is validated on or after 6 August 2026.
Applications received by the Council on or after 6 August 2026 will be considered under the amended requirements.
Applications to vary an existing permission
The new exemptions do not generally allow an existing planning permission to become exempt through an application under section 73 to vary or remove a planning condition.
The BNG position will usually follow the original planning permission. Applicants considering a variation to an existing permission should check the transitional arrangements before submitting their application.
We discuss the changes, including what they mean for applications under section 73, in the latest edition of our Planning Pulse podcast on:
- You Tube : Episode 23 – Biodiversity Net Gain Changes: What You Need to Know Before 6 August
- Spotify : Episode 23 – Biodiversity Net Gain Changes: What You Need to Know Before 6 August
Claiming an exemption
Applicants who consider that their development is exempt from mandatory BNG must identify the relevant exemption on the planning application form and explain why it applies.
The Council may request further information where this is needed to establish whether an exemption applies.
Biodiversity still matters
An exemption from mandatory BNG does not remove the need to consider protected habitats, protected species or other planning policies relating to biodiversity.
Applicants are encouraged to incorporate appropriate measures for wildlife and nature into their proposals, even where mandatory BNG does not apply.
Further guidance
More detailed information is available through the Government’s biodiversity net gain guidance.
https://www.gov.uk/government/collections/biodiversity-net-gain