As a result of a consultation on BNG in 2025, the government is now introducing changes to the legislation that will impact the implementation of BNG, particularly for smaller developments. These changes were announced in April 2026 and are set to come into effect on 6 August 2026.
The most significant change is that developments with a red line boundary of 0.2 hectares or less will now be exempt from mandatory BNG. This will replace the current exemption for self and custom-build developments, which will be removed, though many of these schemes are likely to also fall under the new exemption. In addition, another new exemption will be put in place for temporary developments of 5 years or less, where the land will be reinstated following the development.
There is one notable exception to these exemptions: they only apply if no priority habitat is negatively affected by the development. For example, if a development of less than 0.2 hectares would affect a native hedgerow, which is classified as a priority habitat, it will no longer be exempt from mandatory BNG and will need to achieve a full 10% net gain in all applicable categories.
The BNG hierarchy for small sites will also be changed to make on-site and off-site gains the same level of preference. This means that smaller developments can choose to mitigate by purchasing off-site units without first proving that biodiversity on-site has been maximised.
With these changes, the government aims to reduce the burden on small developments and local authorities. It is expected that a significant number of smaller developments will be exempt from BNG requirements following these changes. Instead, the government is looking to focus resources on large-scale development with more changes planned for later this year, such as introducing BNG for nationally significant infrastructure projects, and updating the statutory biodiversity metric.
It’s worth noting that these changes are not retrospective and only apply to planning applications submitted from 6 August onwards. This means that any applications submitted before this date will continue to be subject to existing BNG legislation, regardless of whether a decision is made before or after 6 August. A consultation on exemption for brownfield developments was also held between April and June 2026; therefore, a government response on the matter is expected in future, potentially leading to future BNG amendments.