Biodiversity Net Gain Exemptions — What Developers & Planners Need to Know 

New Exemptions Coming July 2026

The following new exemptions are expected to be introduced from 31 July 2026, subject to parliamentary scheduling:

A new area-based exemption will exempt all developments on sites of 0.2 hectares or below — regardless of the type of development. This is a significant change that will exempt a large proportion of minor and small-scale development from BNG. It is anticipated that this new exemption will capture many of the self-build and custom-build developments that are currently exempt but will lose that exemption when it is removed. Temporary planning permissions granted for a maximum of five years will also be exempt — recognising that meaningful habitat delivery on temporary development sites is generally not practicable.



Developments with the primary objective of conserving or enhancing biodiversity will also become exempt later in 2026 — the precise timing and detail of this exemption has not yet been confirmed.

Proposed Brownfield Exemption — Consultation Open

The government launched a consultation in April 2026 on a proposed additional exemption for residential development on brownfield land — aligning with the government's brownfield-first approach to housing delivery.

The consultation explored the appropriate definition of brownfield residential development, potential site size thresholds for any exemption, and measures to ensure the exemption minimises negative environmental impacts. The consultation closed on 10 June 2026 and outcomes are expected later in 2026. Until any brownfield exemption is formally introduced through secondary legislation, BNG continues to apply to brownfield residential development in the usual way.

Key Changes to BNG in 2026

The BNG framework is undergoing its most significant changes since it was introduced in February 2024. The following updates are expected to come into effect by 31 July 2026, subject to parliamentary scheduling:

• A new area-based exemption will be introduced for developments on sites of 0.2 hectares or below. The existing exemption for small-scale self-build and custom-build development will be removed — it is anticipated that many of these developments will be captured by the new 0.2 hectare exemption. Temporary planning permissions granted for a maximum of five years will be exempt from BNG. The biodiversity gain hierarchy for minor development will be amended to give on-site and off-site gains equal status. The spatial multiplier will be decoupled from LPA boundaries and aligned with local nature recovery area strategies, allowing developers to source off-site units from a wider area.
• BNG for Nationally Significant Infrastructure Projects — major transport, energy, and water projects — will become mandatory from 2 November 2026. A new consultation on a potential exemption for residential development on brownfield land closed on 10 June 2026, with outcomes expected later in 2026.
• Until these changes are formally implemented through secondary legislation, the current BNG requirements remain in place and developers must continue to follow existing guidance.

What Happens on an Exempt Site

It is important to note that being exempt from the mandatory BNG requirement does not mean a development has no biodiversity obligations. Planning Policy Wales and the National Planning Policy Framework still require all development — including exempt development — to avoid harm to biodiversity where possible, and planning applications will be refused where a significant harm to biodiversity cannot be avoided, mitigated, or compensated for even on an exempt site. Where trees and hedgerows are present on an exempt development site, the need for a BS5837 tree survey and arboricultural assessment remains regardless of the BNG exemption status.

Important Note

The BNG framework is changing rapidly. Until the changes described above are formally implemented through secondary legislation, the current BNG requirements remain in place and developers must continue to follow existing guidance and legislation when delivering BNG. Urban

Tree Management recommends that developers and planners consult their ecological adviser and planning consultant for up-to-date advice on the BNG status of any specific development proposal. The information on this page reflects the position as of April 2026 and will be updated as further changes are confirmed.