From 6 August 2026, a number of important amendments to the mandatory Biodiversity Net Gain (BNG) regime will come into effect in England. These changes, introduced through the Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026, are intended to reduce the administrative burden for the smallest developments while ensuring that important habitats continue to receive appropriate protection.
What is Changing?
New 0.2 Hectare Exemption
One of the most significant changes is the introduction of a 0.2 hectare exemption. Development proposals on sites of 0.2 hectares or less will generally be exempt from the mandatory BNG requirements.
This exemption does not apply where development would adversely affect priority habitat, meaning ecological assessment and biodiversity considerations remain essential for sensitive sites.
Temporary Development Exemption
A new exemption has also been introduced for temporary developments where land will be fully reinstated within five years or less.
Again, this exemption does not apply where priority habitats would be negatively affected.
Greater Flexibility for Minor Development
The biodiversity gain hierarchy has been amended for minor developments that remain subject to mandatory BNG (for example, sites larger than 0.2 hectares).
Previously, developers were generally expected to prioritise delivering biodiversity gains on-site before considering off-site compensation. Under the revised approach, qualifying minor developments may now choose to secure off-site biodiversity gains from the outset, providing greater flexibility where on-site delivery is impractical.
Removal of the Self-Build Exemption
The existing exemption for self-build and custom housebuilding developments has been removed.
As a result, these developments will now be treated in the same way as other qualifying applications and will need to comply with mandatory BNG unless another exemption applies.
What Does This Mean for Local Planning Authorities?
In practical terms, these amendments are not expected to fundamentally alter validation or decision-making processes. However, local authorities are likely to receive fewer BNG submissions for very small developments, reducing the administrative burden associated with assessing biodiversity metrics and gain plans.
Despite these exemptions, biodiversity remains an important material planning consideration.
Developments exempt from mandatory BNG are not exempt from wider ecological legislation or planning policy. Local planning authorities should continue to apply the mitigation hierarchy and ensure that proposals comply with relevant Local Plan policies.
The updated Defra guidance makes this clear, stating that:
“Though we are reducing the BNG burden for the smallest developments, we would still expect these developments to incorporate nature-friendly features.”
It also confirms that exempt developments remain subject to existing environmental protections, and planning permission should still be refused where significant harm to biodiversity cannot be avoided, adequately mitigated or, as a last resort, compensated.
Key Takeaways
- Sites of 0.2 hectares or less are generally exempt from mandatory BNG unless priority habitats are affected.
- Temporary developments lasting five years or less may also be exempt, subject to the same priority habitat safeguard.
- Minor developments that require BNG now have greater flexibility to deliver biodiversity gains off-site from the outset.
- The self-build and custom build exemption has been removed.
- Exempt developments must still comply with ecological legislation, the mitigation hierarchy and Local Plan biodiversity policies.
Further Reading
Further information is available through the following government publications:
- The Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026
- Updated Defra guidance on Biodiversity Net Gain: Exempt Developments
- Defra’s blog explaining the amendments and transitional arrangements
These changes represent a targeted refinement of the BNG framework rather than a wholesale change to biodiversity policy. While they simplify the process for the smallest developments, they reinforce the principle that biodiversity should remain an integral part of the planning process, regardless of whether mandatory BNG applies.
