Biodiversity net gain (BNG) is an established part of the planning system. Subject to statutory exemptions, development is generally required to achieve at least a 10% increase in biodiversity value compared with the pre-development value of a site. This may be delivered through on-site gains, registered off-site gains or statutory biodiversity credits.
Some local planning authorities have adopted policies requiring biodiversity gains above the statutory 10% requirement. There are others that have emerging policies to seek a higher level of gain. Some applicants may have experienced biodiversity gains being sought for development proposals that are exempt from the statutory requirement.
The new National Planning Policy Framework (NPPF), published on 17 August 2026, seeks to establish clearer limits on the circumstances in which ‘local’ BNG requirements may exceed the statutory framework.
Plan-making policy N1(2) of the NPPF states:
“Development plans should only set local standards for biodiversity net gain which are in excess of the statutory net gain requirement where this is for specific site allocations, and is fully justified and deliverable. Local standards should not extend to categories of development which are exempt from statutory biodiversity net gain.”
The policy makes clear that requirements exceeding the statutory level should not apply to all development. Any requirement for a higher level of biodiversity net gain must be limited to a specific site allocation and must be fully justified and deliverable.
National decision-making policy N2(3) of the NPPF reinforces this approach for decision making. Although development proposals may voluntarily incorporate biodiversity enhancements exceeding the statutory objective, an additional gain should only be required where it is established by an up-to-date development plan policy for a specific site allocation.
Importantly, policy N2(3) states that decision makers should not give weight to other development plan policies requiring gains beyond the statutory framework. This expressly includes policies seeking biodiversity gains from developments that are exempt from the statutory requirement.
The distinction between a voluntary enhancement and a mandatory planning requirement is important. Applicants remain free to offer biodiversity improvements above the statutory minimum and these may form part of the overall benefits of a proposal. However, a local planning authority should not require an uplift above 10% unless the development plan meets the specific conditions established by the new NPPF.
The same principle applies to exempt development. Current exemptions include householder applications and, subject to criteria, certain small site, de minimis and temporary developments. As the exemptions changed on 6 August 2026, their scope and application should be considered carefully in each case. Further information is available in our separate piece on them. See here.
For applicants, the new NPPF provides a clearer basis for challenging unsupported local requirements that exceed the statutory framework. If you require advice on a development proposal, please contact us on 01884 212380 or at briandinnis@acornrpc.co.uk. In addition to our planning consultancy services, we have an in-house ecologist who can advise on all aspects of BNG.
