The Government has confirmed a series of important changes to Biodiversity Net Gain (BNG) requirements, coming into force on 6 August 2026. These changes represent the first phase of reforms following the Government’s BNG consultation and are intended to make the system more proportionate, particularly for smaller developments.

Since mandatory BNG was introduced, concerns have been raised about the time, cost, and complexity involved in meeting the requirements on smaller sites. The reforms aim to reduce unnecessary burdens on small developers, landowners, and local planning authorities, while ensuring that larger developments which generally have a greater impact on biodiversity remain the focus for delivering meaningful improvements for nature. For developers and landowners, these changes are important because they may affect whether BNG applies to a project, the costs associated with meeting biodiversity requirements, and how biodiversity considerations are incorporated into development proposals.

Four changes coming into force on 6th August 2026 

1. New 0.2 hectare exemption for smaller developments

What is changing? Developments with a site area of less than 0.2 hectares will no longer be required to deliver mandatory 10% Biodiversity Net Gain, unless the development negatively affects priority habitat on-site. This applies across residential and commercial schemes alike and replaces the previous 25m² de minimis threshold.

How could this affect you? For many small-scale developments, this could remove the need for BNG calculations, biodiversity assessments, and the requirement to secure biodiversity units, thereby helping reduce planning costs, simplify the application process, and improve project timescales. However, an exemption from mandatory BNG does not remove the need to consider biodiversity as part of the planning process. Developments must still comply with relevant planning policies and environmental legislation.

2. New temporary development exemption

What is changing? A new exemption will apply to temporary developments where the land is expected to be restored within five years or less, unless priority habitat is negatively affected (again, unless onsite priority habitat is harmed). This recognises that BNG delivery on short-term sites is of limited practical value.

How could this affect you? Temporary developments that meet the exemption criteria may no longer need to provide mandatory BNG, helping reduce unnecessary cost and administration. However, it will be important to establish at an early stage whether the project qualifies, as the duration of the development and the ability to restore the site will be key considerations.

3. Greater flexibility for minor developments

What is changing? Minor developments that remain subject to BNG requirements (for example, sites over 0.2 hectares) will be able to move directly to off-site biodiversity solutions, rather than having to prioritise on-site delivery first.

How could this affect you? This provides greater flexibility for sites were creating habitats on-site is difficult, impractical, or would compromise the development design. This provides more options when considering the most cost-effective way to meet BNG requirements, although off-site biodiversity units will still need to be secured where required.

4. Removal of the self and custom build exemption. 

What is changing? The existing exemption for self- and custom-build dwellings is being removed, as most such schemes will now fall under the new 0.2ha threshold.

How could this affect you? Some projects which previously fell outside the BNG requirements may now need to consider biodiversity impacts as part of their planning strategy.

Transitional Arrangements

The changes will apply only to planning applications submitted on or after 6 August 2026.

Applications already submitted before this date will continue to be assessed under the existing BNG legislation. The reforms will not apply retrospectively to existing applications or permissions.

For clients preparing new planning applications, understanding which rules apply at the point of submission will be important when considering project costs, timescales, and development strategy.

Our Perspective

These reforms represent a positive step towards making BNG more proportionate and practical. While BNG remains an important tool for ensuring development contributes to nature recovery, the previous requirements created challenges for some smaller and temporary developments in terms of cost, complexity, and administration.

By reducing unnecessary burdens on lower-impact schemes and maintaining stronger requirements for larger developments, the changes should help create a more balanced and effective system. However, biodiversity will remain an important consideration within the planning process, and the most successful projects will continue to address ecological matters at an early stage. BNG remains a divisive issue due in part to how the metric works and how it is ultimately secured, often through s106 agreements rather than condition, these changes do offer some welcome relief for smaller developments.

How We Can Help

The key for developers and landowners is to understand early whether BNG applies to their project and how the new rules may affect costs, design decisions, and the planning strategy. 

With the BNG framework continuing to evolve, early advice is essential. We can help you understand how the changes apply to your project, identify whether exemptions may be available, and advise on the most appropriate approach where BNG requirements remain. By considering biodiversity requirements at an early stage, we can help reduce uncertainty, manage risks, and support a smoother planning process.

Contact our team by emailing planning@union4.co.uk