Overview: what's changing and when
Two years into mandatory BNG, the government is making its most significant package of reforms to the system. The changes range from expanding exemptions for small sites to extending BNG to the largest infrastructure projects in England. Here's the full picture:
| Reform | Status | Expected timeline | Impact |
|---|---|---|---|
| 0.2 hectare exemption | Confirmed | Late 2026 | High — exempts many small and medium developments |
| BNG for NSIPs | Confirmed | May 2026 | High — extends BNG to major infrastructure |
| Brownfield exemption | Consultation | Under consultation, 2026 | Medium — could exempt residential brownfield up to 2.5ha |
| Streamlined off-site delivery | Confirmed | 2026 | Medium — simplifies processes for small/medium developments |
| LNRS integration | In progress | Throughout 2026 | Medium — affects strategic significance scoring in the metric |
| NPPF changes | Proposed | 2026–2027 | Medium — may limit LPA ability to require above 10% locally |
| Open mosaic habitat review | Consultation | 2026 | Medium — could simplify brownfield BNG compliance |
The reforms in detail
New 0.2 hectare area-based exemption
The current de minimis threshold of 25 square metres is being replaced with an area-based exemption for sites under 0.2 hectares (approximately 2,000 sqm). This is an 80-fold increase that will exempt a large number of small residential developments, urban infill projects, and minor commercial schemes from BNG requirements entirely.
The Housing Secretary confirmed this change in December 2025. It is expected to take effect in the latter half of 2026, though the exact implementation date and transitional arrangements have not yet been published.
BNG mandatory for NSIPs
Nationally Significant Infrastructure Projects — the largest developments in England, consented through Development Consent Orders under the Planning Act 2008 — will be required to deliver 10% biodiversity net gain from May 2026. This includes energy, transport, water, and waste infrastructure above prescribed thresholds.
The regime broadly mirrors the existing TCPA framework but with adaptations for the scale and complexity of major infrastructure, including flexibility on the delivery hierarchy and provisions for phased BNG plans. The government consultation ran until July 2025, with a response expected alongside the implementation date.
Targeted brownfield exemption
A rapid consultation on a targeted BNG exemption for residential developments on brownfield sites up to 2.5 hectares was announced for early 2026. This responds to widespread industry concern that BNG compliance costs are disproportionately impacting brownfield housing delivery — particularly on sites with open mosaic habitats.
Open mosaic habitats on previously developed land can score as Medium distinctiveness in the metric, requiring developers to offset losses with Medium or higher habitat even when the site appears to be derelict wasteland. This has been one of the most contentious aspects of BNG and a significant cost driver for brownfield-first housing policy.
Open mosaic habitat definition review
Alongside the brownfield consultation, the government has indicated that the definition of open mosaic habitat will be revisited to provide greater clarity, alongside a potential relaxing of the trading rules relating to these habitats.
This is significant because the current definition captures a broad range of brownfield sites that many developers and LPAs consider inappropriate for Medium distinctiveness treatment. A clearer definition could substantially reduce BNG costs on many brownfield developments.
Streamlined off-site delivery
The government has confirmed measures to streamline off-site BNG delivery for small and medium developments. Details are awaited but this is expected to simplify the process of purchasing and allocating off-site biodiversity units, potentially reducing the administrative burden on both developers and LPAs.
Local Nature Recovery Strategies
Over half of all Local Nature Recovery Strategies (LNRS) have now been adopted across England, with the remainder expected to be in place during 2026. LNRSs identify priorities and locations for nature recovery and directly influence the strategic significance multiplier in the biodiversity metric.
Proposed changes to the NPPF would give greater weight to LNRSs in plan-making and decision-making. Early adopters are already exploring how to use the private BNG market alongside public funding to deliver LNRS priorities at scale.
NPPF changes affecting BNG
Proposed changes to the National Planning Policy Framework may restrict the ability of local authorities to push mandatory BNG beyond 10% through local plans. Under current rules, some LPAs have set higher local BNG targets — the reforms would limit this to certain allocations where it is justified and deliverable.
The government has also stated that BNG is not in scope of broader planning reform deregulation, providing some stability for the core 10% requirement.
What this means for each stakeholder
| Stakeholder | Key impacts | Action needed |
|---|---|---|
| Developers (small sites) | Many will become exempt under the 0.2ha threshold. Brownfield exemption could remove costs for residential brownfield up to 2.5ha. | Check whether your sites fall under the new thresholds. Don't delay applications expecting retrospective exemptions — they are unlikely. |
| Developers (large sites / NSIPs) | NSIPs gain new BNG obligations from May 2026. Off-site demand will increase significantly at the higher-distinctiveness tiers. | Begin BNG planning immediately for any NSIP in design stage. Engage with the off-site market early for large-volume requirements. |
| Landowners / habitat banks | Reduced demand from small sites may be offset by major new NSIP demand. LNRS alignment could boost strategic significance scoring on some sites. | Check your LNRS alignment. Consider positioning habitat bank offerings for NSIP-scale demand. Review unit pricing in light of market changes. |
| LPAs | Administrative burden reduced on small sites. NPPF changes may limit above-10% local requirements. LNRS adoption creates new strategic planning priorities. | Prepare for NSIP-related consultation requests. Update local guidance to reflect new exemption thresholds once confirmed. |
| Lenders | Reduced BNG cost risk on small developments. New NSIP obligations create additional due diligence requirements for infrastructure finance. | Update risk frameworks to reflect new exemption thresholds. Build NSIP BNG awareness into infrastructure lending processes. |
Impact on the BNG market
The combined effect of these reforms on the off-site unit market is complex:
- Demand reduction from small sites as the 0.2ha exemption takes effect and potentially brownfield sites become exempt — this could reduce unit demand in areas dominated by small developments
- Demand increase from NSIPs, which may require hundreds or thousands of units per project, particularly for higher-tier habitats
- Geographic redistribution as NSIP demand may concentrate along infrastructure corridors rather than around urban development hotspots
- Quality shift toward higher-distinctiveness and bespoke habitat solutions driven by NSIP requirements, rather than the standard grassland and scrub that dominates the current market
- Pricing dynamics may shift as the market matures — Savills data already shows healthy national supply (~28,000 units) but geographic concentration issues. NSIP demand could tighten supply in specific corridors
Keeping up to date
We will update this page as new details are published on each reform. To stay informed:
- Subscribe to our weekly newsletter for BNG policy updates and market intelligence
- Follow the GOV.UK BNG collection for official guidance updates
- Check the LGA/PAS BNG hub for LPA-focused implementation guidance
- Visit ectare.dev for live market data reflecting the impact of reforms on unit availability and pricing