Biodiversity Net Gain (BNG): Key updates and what this means for our clients
Two years on from becoming mandatory, Biodiversity Net Gain (BNG) is no longer a new policy requirement. Since its introduction in 2024, BNG has shaped how sites are assessed, designed and brought forward.
The Government’s latest package of updates, comprising the April 2026 response to the consultation on improving BNG implementation, confirmation of BNG for Nationally Significant Infrastructure Projects (NSIPs), and a new live consultation on a potential exemption for brownfield residential development, sets out a refinement of how and when BNG is applied.
These changes do not alter the principle of BNG, but respond to industry feedback that in some cases the cost and complexity of BNG have been disproportionate, particularly for smaller and more constrained sites. The focus is on making the system more practical, while maintaining its core objective of delivering measurable gains for biodiversity.
For clients, the key issue is how these updates will impact the viability, risk and the way development schemes are brought forward.
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A more proportionate approach
The most immediate changes arise from the April 2026 Government response to the consultation on improving BNG implementation for minor, medium and brownfield development.
A key reform is the introduction of a 0.2 hectare area-based exemption, expected to come into force before 31 July 2026 (subject to legislation). The exemption is intended to remove the BNG requirement from smaller scale developments, where the administrative burden and cost are often highest relative to the scale of impact. The Government estimates that this could exempt around 50% of residential planning permissions that would otherwise have been subject to BNG.
In practical terms, this is likely to have significant implications for how smaller schemes are brought forward once the exemption takes effect. Applications below the 0.2 hectare threshold may no longer need to factor in the cost of accommodating on-site or off-site biodiversity measures or undertaking detailed BNG and ecology assessments, which could improve viability and reduce delays currently experienced.
Another change expected to be introduced by the end of July 2026 is the removal of the existing exemption for small-scale self-build and custom build development. This is intended to simplify the system and address concerns that the exemption was difficult to administer and open to misuse. In practice, many of these schemes are expected to fall within the new 0.2 hectare area-based exemption instead.
In addition, targeted exemptions will be introduced for temporary planning permissions of up to five years to prevent a disproportionate burden and cost pressure resulting from implementing BNG measures.
These changes should not be interpreted as biodiversity and ecological considerations falling away entirely. National policy and the mitigation hierarchy will still apply, meaning ecological impacts will continue to be a material planning consideration within the decision-making process.
Greater flexibility in delivery
A key change to BNG we should expect to see by the end of July 2026 is an increased flexibility in how BNG can be delivered. The biodiversity gain hierarchy will be amended so that off-site provision is given equal weight to on-site delivery for minor developments.
This is a practical shift. On smaller-scale sites, on-site provision can be difficult to deliver effectively. Greater flexibility to rely on off-site units should allow biodiversity measures to be delivered in a more proportionate and effective way, while reducing pressure on more constrained site layouts and providing more certainty in viability assessments and negotiations with local authorities.
As the off-site market continues to develop through increased third-party suppliers of BNG credits, this could become a more standard route to delivering BNG on smaller sites.
BNG and nationally significant infrastructure projects
Separately, the Government has confirmed that BNG will apply to nationally significant infrastructure projects (NSIPs) from November 2026, having originally consulted on implementation from May 2026
This follows a consultation which took place between 28 May and 24 July 2025 and introduces a mandatory framework for delivery biodiversity gains on major infrastructure schemes, including transport, energy and water infrastructure. While BNG has already applied across ‘standard’ planning applications since February 2024, NISPs had previously remained outside of the regulations.
The Government response indicates that the framework for NSIPs has been designed to reflect the scale and complexity of such schemes. In particular, the framework will focus on habitats directly impacted by development, rather than applying across the entire red line boundary of a scheme. The framework will also allow retained, enhanced and newly created on-site habitats to contribute towards BNG delivery.
Brownfield development: a potential step change
Along with the Government’s published updates, Defra has also launched a new consultation on a targeted exemption for residential development on brownfield land, seeking views on whether such schemes should be partially or wholly exempt from BNG and what thresholds might apply.
This is particularly significant given the Government’s wider focus on the delivery of schemes on brownfield land.
In practice, BNG has often presented challenges on brownfield sites, including limited opportunities for on-site habitat creation and a greater reliance on delivering off-site BNG units, leading to higher relative costs on already constrained sites.
If introduced, a targeted exemption could materially affect the delivery of schemes proposed on brownfield sites. However, the outcome remains uncertain until the consultation has concluded, the feedback has been published and the Government has provided an update on next steps. For now, applicants are advised to continue to consider BNG from the outset of scheme development, while monitoring how this develops. The consultation will close on 10th June 2026.
What this means for our clients
Taken together, these change point towards more flexible, BNG regulations.
In practice, small sites could benefit from reduced costs and complexity. Brownfield schemes may see more significant change, but this will be dependent on the outcome of the current consultation. Larger developments, which soon will include NSIPs, will continue to require a clear and robust BNG strategy from the outset. Off-site provision is likely to become a more mainstream mechanism for the delivery of BNG.
The proposed BNG reforms indicate that the system that is being refined to better reflect viability, deliverability and proportionality, while maintaining its core objective of delivering measurable improvements for biodiversity.
The direction of travel is towards a more proportionate approach to applying BNG, however many of the changes will require secondary legislation and updated guidance to be published before the full detail and practical implications are clear. How these changes are implemented in practice will therefore be important to monitor over the coming months.
For clients, this is a broadly positive shift. However, it remains important to adopt careful, considered site-specific BNG strategies, particularly while the legislative and policy framework continues to evolve.
If you have any queries regarding Biodiversity Net Gain please get in touch with the authors of this legal article Maisie McCann, Mark Harris or another member of our Planning & Environmental Law team.
The content of this page is a summary of the law in force at the date of publication and is not exhaustive, nor does it contain definitive advice. Specialist legal advice should be sought in relation to any queries that may arise.
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