More than two years after mandatory Biodiversity Net Gain (BNG) became part of the planning landscape, the latest legislative changes show that the regime is still evolving. From 6 August 2026, several amendments will come into force, intended to make the process more proportionate for the smallest developments and less burdensome for local planning authorities, while keeping the focus on meaningful biodiversity improvements for larger schemes.
From a planning perspective, the changes are welcome. They should help some straightforward applications move more quickly, giving clients greater certainty and, in some cases, helping them start on site sooner. However, this is not the wholesale simplification some may have hoped for. The detail still matters, and BNG will remain an important consideration from the earliest stages of many projects.
What is changing?
The most notable change is a 0.2-hectare exemption for developments on sites of 0.2 hectares or less, provided no priority habitats are affected. There will also be an exemption for certain temporary developments where land will be reinstated within five years, subject to the same important caveat around onsite priority habitat.
For minor developments that are not exempt, the biodiversity gain hierarchy will become more flexible, allowing some schemes to secure off-site mitigation from the outset. At the same time, the self and custom build exemption will be removed, so those developments will need to meet mandatory BNG requirements unless another exemption applies.
The changes will apply only to new planning applications made on or after 6 August 2026. Applications submitted or permitted before then will continue under the existing legislation, and the position will apply to most variations where the original permission predates that date.
Two years of BNG in practice
Since BNG became mandatory, it has moved from policy concept to practical planning requirement. It now shapes site appraisals, design strategies, viability discussions, legal agreements and pre-commencement programmes. For clients, the question is no longer simply whether BNG applies, but how it can be addressed in a commercially realistic, deliverable way.
BNG is not just an ecological calculation; it is a planning, design and delivery issue. Early decisions can affect whether BNG can be accommodated on site, whether off-site units are needed, whether legal agreements are required, and whether the programme is exposed to avoidable delay.
Why the latest changes are helpful, but limited
The 0.2-hectare exemption should remove some smaller, lower-impact schemes from the mandatory BNG process. Where it applies, it should reduce information requirements, simplify validation and decision-making, and help avoid disproportionate cost and delay.
However, the exemptions are tightly framed. The temporary development exemption may help with temporary accesses, construction compounds or short-term operational requirements, but it will not apply where priority habitat is negatively impacted. As many native hedgerows can be priority habitats, a scheme that looks straightforward may still need to address BNG fully.
Challenges for clients
The main challenge remains certainty. Clients need to understand early whether BNG applies, what the baseline position is, whether on-site delivery is achievable, and whether off-site solutions are likely to be required. If left too late, BNG can affect layout, land take, cost, legal agreements and the point at which development can commence.
There is also a resourcing challenge within the planning system. Local planning authorities have had to absorb a new technical requirement while already under pressure. The latest exemptions may help with the smallest applications, but larger and more complex schemes will still require robust information and close coordination between planning, ecology, design and legal teams.
BNG can also influence viability, particularly where on-site delivery competes with developable area or off-site units are required. Availability, location and cost of off-site mitigation will remain important, especially where local supply is limited.
Opportunities for clients
Despite these challenges, BNG creates opportunities. For development clients, early planning can turn BNG from a compliance hurdle into part of a stronger, more resilient scheme. Well-considered green infrastructure, habitat creation and landscape design can support planning arguments, improve placemaking and create long-term value.
For landowners, BNG continues to present a diversification opportunity where land is suitable for habitat creation or enhancement. As the market matures, the strongest opportunities are likely to be strategically located, ecologically deliverable and aligned with local demand.
The more flexible hierarchy for minor development may also give clients greater choice. Considering off-site mitigation earlier could be beneficial where on-site delivery would compromise layout or viability, provided the approach is robust, proportionate and capable of being secured.
What should clients do now?
Clients with schemes in progress should review application timings carefully. For some projects there may be a benefit in proceeding under the current regime; for others, the new exemptions or hierarchy changes may be relevant.
The key message is to assess BNG early: understand whether an exemption genuinely applies, identify any priority habitats, consider implications for design and programme, and decide whether on-site or off-site delivery is likely to be most appropriate.
Further changes are expected, including potential exemptions for biodiversity-led development and improvements to parks, playing fields and public gardens, plus updates to the statutory biodiversity metric. The government has also consulted on a possible targeted exemption for some residential brownfield development.
Associate Partner in our planning team, Jenny Occleshaw, said: “The latest BNG changes are a sensible step towards a more proportionate system, particularly for smaller and more straightforward applications. Anything that helps reduce unnecessary complexity and supports timely planning decisions is welcome.
“However, clients should not assume the changes remove the need for early advice. The exemptions have important limitations, and in many cases the practical planning position will remain largely unchanged. BNG is now embedded in the planning process, and the best outcomes will come from identifying the issues early and aligning planning, ecology and commercial considerations from the outset.
“For our clients, the opportunity is to treat BNG not simply as a planning obligation, but as part of the wider project strategy. Done well, it can support better schemes, smoother delivery and more lasting value.”