Government Announces Changes to BNG: New Exemptions and a Shift Towards Off-Site Delivery
The government has announced a significant package of updates to Biodiversity Net Gain, following its 2025 consultation. The direction of travel for BNG is a simpler system, with fewer burdens on smaller sites, and off-site delivery becoming a more practical and accepted route.
Overall, the changes are positive, particularly for those with interests in smaller sites.
What’s changing?
At a high level, the reforms seek to expand exemptions for smaller and low-impact development, to make it easier to deliver BNG off-site, and to streamline parts of the metric.
The headline change is a new area-based exemption for sites of 0.2 hectares or less. This is expected to remove around half of previously eligible residential schemes from BNG requirements. Importantly, this isn’t just an extension of the existing de minimis rules; it’s a separate exemption.
Alongside this, the self-build and custom-build exemption will be removed, meaning most of these smaller schemes will now fall within the new 0.2ha threshold.
The de minimis exemption remains unchanged for now. However, the government has signalled that further adjustments may follow, including a potential low-impact exemption for certain larger sites with limited biodiversity effects.
The intention is to reduce the disproportionate costs and administrative burden on small sites, while allowing LPAs to focus resources on larger schemes where greater biodiversity gains can be achieved.
Additional exemptions coming forward
Additional targeted exemptions will be introduced, including for temporary permissions (<5 years), biodiversity-led development, and improvements to parks, playing fields and public gardens where no priority habitats are affected.
A shift in how BNG is delivered
Significantly, the biodiversity gain hierarchy will be amended so that off-site biodiversity gains sit on an equal footing with on-site delivery, rather than a fallback option. Statutory credits will continue to sit firmly as the last resort.
In practical terms, this should make it easier to rely on off-site solutions where on-site delivery is constrained or inefficient, and reduce the need for complex negotiations over marginal on-site gains.
To support this shift, the government is also changing how the spatial risk multiplier works. Instead of being based on local planning authority boundaries, it will now operate at the level of Local Nature Recovery Strategy areas. This expands the geography for sourcing off-site units, improving flexibility while still keeping delivery broadly local.
Changes to the metric
Alongside policy changes, there is a clear push to simplify the technical operation of BNG.
This includes moving towards a digital metric tool, simplifying certain assessment processes, and making river condition assessments more proportionate. Work is also ongoing to improve how brownfield sites and open mosaic habitats are treated, including clearer definitions and the potential introduction of a new urban habitat category.
When will this happen?
For now, nothing has changed. The government is taking a phased approach, with the first reforms expected to come through relatively soon.
Defra has said it plans to introduce secondary legislation before the summer recess in 2026, with the aim of bringing the initial changes into force before 31 July 2026.
These first changes will include the new 0.2-hectare exemption, removal of the self and custom build exemption, exemptions for temporary permissions, and updates to the biodiversity gain hierarchy for minor development.
A second wave is expected later in 2026. This is likely to cover the additional exemptions discussed above, and possibly further changes, such as tweaks to the de minimis threshold or a targeted exemption for residential brownfield schemes, depending on how the consultation lands.
Updated guidance, forms and templates will follow, along with advice on how to deal with schemes caught in the transition.
Taken together, these changes point to a more flexible and proportionate BNG regime. For developers, that should mean fewer constraints on smaller sites and more realistic delivery options where on-site provision is limited.
That said, much will depend on how the detail is implemented, particularly around exemptions and the evolving role of off-site delivery.
For further advice on Biodiversity Net Gain, please contact tor&co.
enquiries@torandco.com
Emily Comber MRTPI
Senior Planner