Key facts
- Effective date
- May 2026 (delayed from November 2025)
- Minimum gain
- 10% biodiversity uplift, measured using the statutory metric
- Legal mechanism
- Amendments to the Planning Act 2008 via the Environment Act 2021
- Consent route
- Development Consent Orders (DCOs), not TCPA planning permissions
- Duration
- Gains must be secured for at least 30 years
- Scope
- Energy, transport, water, waste, and wastewater infrastructure above prescribed thresholds
- Exclusions
- Marine environment beyond the intertidal zone; applications submitted before May 2026
What are NSIPs?
Nationally Significant Infrastructure Projects are major infrastructure developments in England that are consented through Development Consent Orders (DCOs) under the Planning Act 2008, rather than through the normal TCPA planning permission route. They include:
- Energy: Power stations, wind farms, solar farms, and electricity transmission above prescribed capacity thresholds
- Transport: Major highways, railways, airports, and ports
- Water: Reservoirs, water treatment works, and transfers above prescribed volumes
- Waste: Large-scale waste and wastewater facilities
NSIPs are the largest and most complex developments in England. Their scale — which can span hundreds or thousands of hectares — creates unique challenges for BNG delivery that the government has sought to address through a tailored framework.
Timeline and delays
BNG for NSIPs has had a lengthy road to implementation:
- The Environment Act 2021 included provisions to extend BNG to NSIPs
- The government initially delayed implementation by two years (compared to TCPA developments) to give NSIP promoters time to prepare
- In June 2025, DEFRA postponed the start date from November 2025 to May 2026, citing the need for a clearer framework
- A government consultation on the detailed NSIP BNG regime ran until July 2025
- The Environmental Improvement Plan 2025 confirmed the May 2026 timeline
How NSIP BNG differs from standard BNG
While the core principles are the same (10% uplift, 30-year securing, statutory metric), the government has proposed several modifications to recognise the unique characteristics of NSIPs:
| Feature | TCPA developments | NSIPs (proposed) |
|---|---|---|
| Pre-development value | Habitats within the red-line boundary | All habitats within the entire order limits (which may be significantly larger than the actual construction area) |
| Delivery hierarchy | On-site first, then off-site, then credits | Greater flexibility to deliver on-site or off-site from the outset, given the scale and complexity of NSIP boundaries |
| Temporary land use | Not a significant issue | Major consideration — NSIPs often use land temporarily during construction that must be restored afterwards. The government is consulting on how to treat this |
| Gain plan | Submitted once for approval | Must be submitted and updated as the project progresses, with potential for phased approval reflecting the longer NSIP construction timescales |
| Policy framework | NPPF and local plans | Biodiversity gain statements incorporated into National Policy Statements for each NSIP sector |
| Decision maker | Local Planning Authority | Secretary of State (who may refuse a DCO if BNG objectives are not met) |
| Irreplaceable habitats | BNG does not apply; bespoke compensation required | Same — BNG objective does not apply to irreplaceable habitats; existing protections remain |
The order limits challenge
One of the most significant issues for NSIP BNG is the treatment of order limits — the formal boundary of the DCO application. For many NSIPs, the order limits encompass far more land than will actually be built on. A linear infrastructure project like a highway or railway may have order limits extending hundreds of metres either side of the actual construction corridor to accommodate temporary works, environmental mitigation, and utility diversions.
The government has proposed that all habitats within the entire order limits are included in the pre-development biodiversity value calculation. This means promoters may need to achieve 10% net gain across a much larger area than the actual footprint of permanent works — a potentially significant cost increase.
The government is seeking evidence on alternative approaches to this calculation, recognising the potential for disproportionate impact.
Off-site delivery and market impact
NSIPs are expected to generate substantial demand for off-site biodiversity units. The scale of these projects means that on-site delivery alone will rarely be sufficient to achieve the full 10% uplift, particularly where projects conflict with rare or high-distinctiveness habitats.
However, the nature of NSIP demand may differ from standard development:
- Scale: Individual NSIPs may require hundreds or thousands of units — far more than a typical housing development
- Habitat complexity: NSIPs frequently conflict with rare or irreplaceable habitats, requiring bespoke rather than off-the-shelf solutions
- Geographic spread: Linear infrastructure projects may cross multiple LPAs and NCAs, creating complex geographic matching requirements
- Timing: NSIP construction timescales are typically much longer than standard developments, meaning BNG delivery may need to be phased
As a result, Savills and other analysts anticipate that NSIP BNG will drive made-to-order and bespoke off-site solutions rather than reliance on existing habitat bank stock.
Voluntary early adoption
Although BNG is not yet mandatory for NSIPs, many promoters have already begun incorporating biodiversity commitments into their DCO applications on a voluntary basis. The Bramford to Twinstead Reinforcement Project provides an instructive example: National Grid voluntarily committed to delivering 10% BNG, and the Secretary of State's Decision Letter in September 2024 supported this commitment, even granting compulsory purchase powers for BNG delivery land.
This precedent suggests that voluntary BNG commitments in DCO applications are likely to be looked on favourably by the examining authority, even before the mandatory requirement takes effect.
Practical guidance for NSIP promoters
- Begin BNG planning at the earliest design stage. The scale and complexity of NSIPs means that retrofitting BNG into an advanced design is far more expensive and disruptive than embedding it from the outset.
- Map your habitats early. Understanding the baseline biodiversity value across the full order limits is essential for accurate cost forecasting and design optimisation.
- Engage with the off-site market early. Securing large volumes of off-site units takes time, particularly for higher-tier habitats. Early engagement with habitat bank operators and landowners is critical.
- Consider phased delivery. The proposed framework allows for phased BNG plans — use this to align biodiversity delivery with construction staging.
- Distinguish BNG from other mitigation. The Bramford to Twinstead example highlights the importance of clearly separating BNG proposals from other habitat mitigation, reinstatement, and compensation measures in the DCO application.
- Plan for 30-year securing. Off-site gains must be secured through conservation covenants or S106 agreements alongside long-term management and monitoring plans.
What happens next
The government is expected to publish its response to the NSIP BNG consultation alongside the final biodiversity gain statement text that will be incorporated into National Policy Statements. Key outstanding questions include:
- The final approach to calculating pre-development value across order limits
- Detailed rules for the treatment of temporarily used land
- The process for phased BNG plan submission and approval
- Whether any sector-specific modifications will apply
We will update this page as new guidance is published. For the broader picture of all 2026 changes, see our 2026 reforms guide.