BNG for NSIPs: Key Guidance and Next Steps Ahead of November 2026

June 2026 Update

In June 2026, DEFRA published the final biodiversity gain statements and supporting guidance for Nationally Significant Infrastructure Projects (NSIPs).

Together with the secondary legislation laid earlier this year, these documents formally confirm that mandatory Biodiversity Net Gain will apply to NSIP applications submitted from 2 November 2026.

The guidance provides additional detail on how biodiversity baselines should be established, how gains can be delivered and reported, and how NSIPs will interact with the wider BNG framework.

For developers and landowners trying to understand what this actually changes, this article breaks down ten decisions that materially affect how BNG will work for major infrastructure, what changed between consultation and final policy, and why those changes matter commercially.

The Headline: November 2026, not May

BNG will apply to NSIP applications made on or after 2 November 2026. Since the government response was published, biodiversity gain statements have now been laid before Parliament and accompanying guidance has been released, providing additional clarity on how the regime will operate in practice.

Six months of extra preparation time changes the calculus for any developer with an NSIP application in the pipeline for late 2026 or 2027, and it alters the demand curve that off-site providers have been planning against.

The new date does not reduce the scope of what BNG will require, nor will it introduce a transitional regime for half-prepared applications. And it does not mean the preparation window has loosened - DCO applications take years to examine, which means design decisions being made now are already effectively within the BNG framework.

What Changed Between Consultation and Outcome

Several material shifts occurred between May 2025 and April 2026, and the commercial implications are significant. These are the ten decisions that matter most.

• 1. A single framework for all NSIPs

  Defra has decided to apply a consistent BNG requirement across all NSIP types without exemptions or voluntary approaches including nuclear, renewables, transport and water.

  Why it matters: Every NSIP developer now operates under the same rules as the wider BNG regime. That creates demand uniformity across the off-site unit market. A single framework reduces complexity, creates a level playing field between sectors, and aligns NSIPs with the existing Town and Country Planning regime.

  For developers, this means the rules are the rules regardless of what is being built. For landowners and off-site providers, it means demand will not be fragmented across sector-specific metrics or requirements - every NSIP will be drawing from the same unit market.

• 2. BNG stays at 10% for NSIPs

  Despite heavy RSPB campaign pressure for a higher threshold, Defra has decided to retain the biodiversity gain objective at 10%. Defra’s state reasons: maintaining alignment with the TCPA regime ensures consistency and provides certainty for developers and stakeholders. In practical terms, it means NSIPs will be enter the same unit market as any other development requiring BNG, rather than a separate higher-ambition tier.

  Why it matters: This is a commercially significant decision. NSIPs will enter the same unit market as TCPA developments - not a separate higher-ambition one. A different objective could fragment the market and create pricing pressure on specific unit types.

• 3. The 'BNG boundary' replaces the full Order limits

  This is arguably the most consequential technical change from the consultation to the final rules. Defra originally proposed that all habitats within the DCO order limits would need to be included in the pre-development baseline. The final rules walk this back.

  Under the new approach, unimpacted habitats do not need to be included in the BNG baseline - only habitats that are negatively impacted by the development, or used to contribute towards BNG, need to be included. The 10% BNG requirement will therefore apply to a smaller area, referred to as the BNG boundary. Unimpacted habitats within the Order limits do not need to be included, though developers can choose to include them voluntarily.

  What it means: For linear, NSIPs, this is a meaningful win on proportionality. A project with 500 hectares of Order limits but only 50 hectares of actual habitat impact now calculates BNG against the 50-hectare figure, not the full 500. This reduces the number of units required, and therefore the scale of off-site procurement.

  But: Applicants must now submit a BNG boundary plan as part of their outline biodiversity gain plan, clearly distinguishing impacted, contributory, retained and excluded habitats. This demands careful early-stage mapping - a point developers and their ecologists should plan for from the outset.

  Since publication of the final guidance, additional clarity has been provided on how BNG baselines should be established for NSIPs. Unlike many traditional planning applications, not all land within the Order Limits will necessarily need to be assessed for BNG purposes. This reflects the unique nature of major infrastructure projects and provides greater certainty around how biodiversity impacts should be measured and reported.

• 4. Off-site can now be a 'first-instance' strategy

  The consultation originally proposed that NSIP developers could deliver BNG on-site or off-site in the first instance, and the final rules confirm this approach. This represents a real departure from how BNG operates for TCPA developments.

  For a standard residential or commercial scheme, the mitigation hierarchy strongly favours on-site delivery. Off-site provision is permitted, but the system is designed to push developers to look there second. For NSIPs, Defra has explicitly recognised that the scale of major infrastructure may produce better ecological outcomes through strategic off-site delivery and has therefore legitimised of-site as a first-instance option.

  Statutory biodiversity credits still remain a last-resort mechanism, available only when on-site and off-site routes have been exhausted.

  Why it matters: This is a green light for strategic procurement rather than a nudge toward on-site-first decision-making. The practical implication is that NSIP developers have explicit regulatory permission to build their BNG strategy around strategic off-site units from day one, where this produces the best commercial and ecological outcome.

• 5. No spatial risk multiplier penalty across LPAs for area-based habitats

  The spatial risk multiplier reduces the biodiversity value of off-site units the further they are located from the development site. For a linear NSIP crossing six LPAs, this has historically created a procurement nightmare - each LAP separate spatial consideration, each NCA a different multiplier calculation, each off-site arrangement a standalone commercial transaction.

  NSIPs can allocate off-site biodiversity gains, from any LPA, NCA (soon to be switching to any LNRS in line with other BNG reforms outlines) or Marine Plan Areas the NSIP BNG boundary is located within, to their development without triggering additional spatial risk multiplier penalties within that boundary.

  Why it matters: A cable route crossing six LPAs no longer needs six separate compliance strategies. Developers can source units from a single habitat bank anywhere along the route without taking a spatial risk penalty. This is a major procurement simplification.

  Exception: Watercourse units still must be compensated within the same catchment. Defra will not be changing how the spatial risk multiplier applies to watercourse units where a project spans multiple catchment areas as previously proposed.

• 6. Temporary land gets a pragmatic solution

  A recurring concern throughout the consultation was how to handle land that NSIPs occupy temporarily - construction compounds, cable laydowns, access routes that get restored once the project is operational. The challenge is that BNG requires 3-year security, but the land itself returns to the previous owner long before that. Defra’s response:

  • All on-site habitat creation and enhancement counted towards the post-development biodiversity value is to be considered significant and must be legally secured.

  • 10% BNG is still required on temporarily used land, as it has been impacted by the development. But as per existing BNG requirements, these can be delivered anywhere on-site or off-site or through statutory biodiversity credits as a last resort.

  • The temporary-loss rule has been extended: There is an existing rule that allows habitats which are temporarily impacted and the nrestored to their previous habitat and condition within 2 years to be counted as retained - for NSIPs, this will be extended to 5 years for habitats of low and very low distinctiveness.

  Why it matters: Temporary impacts still count towards the 10%, but developers can discharge that requirement through off-site units rather than trying to secure 30-year gains on land that will revert to farmers.

• 7. Outline plan at application, updated plan before commencement

  One of the more common objections during consultation was the impracticality of submitting a fully worked-up biodiversity gain plan at DCO application stage, when many design details are still uncertain.

  The final rules adopt a staged approach. Applications submit an outline biodiversity gain plan with the DCO application. Before commencement of development - or each phase, for phased projects - an updated or phase biodiversity gain plan is submitted for approval. Any final shortfall in units is calculated and secured before operation at the latest.

  Why it matters: This is a staged approach. Developers don’t need to lock in at DCO submission - but they do need a credible strategy, and the clock keeps running. This is more flexible than the consultation proposed, but the flexibility is around when final unit allocations are locked in - not whether they are required.

• 8. Discharging authority flexibility

  This role may now be fulfilled by any relevant planning authority, such as the host LPA or a lead LPA (for projects spanning multiple authorities). Alternatively, the role could be fulfilled by the Secretary of State, in consultation with relevant planning authorities.

  Why it matters: This avoids the gridlock of multiple LPAs having to agree on post-consent decisions. It also gives promoters flexibility to propose a workable discharging arrangement at the pre-application stage.

• 9. Qualified ecologists formally required

  A new requirement: applicants must confirm within the biodiversity gain plan how qualified ecologists have contributed to the development of the plan, the metric calculation, and the habitat management and monitoring proposals.

  The change reflects consultation feedback about inconsistent quality of BNG submissions under the TCPA regime, and Defra’s intent to hold NSIPs to a higher evidential standard given the scale of impact involved.

  Why it matters: This ends any ambiguity about whether ecological input is optional - it isn’t.

• 10. Excess gains can be registered and traded

  If a development delivers more than the 10% minimum on-site, the excess can either be attributed to the development as additional gain, or legally secured, registered and sold as off-site gain for another development. Applicants need to confirm which approach applies in their outline biodiversity gain plan.

  Why it matters: This creates an interesting supply-side dynamic. NSIP promoters with land-rich sites - particularly solar, reservoir, or rural infrastructure developments - can effectively become off-site providers themselves, recouping some of their BNG cost by selling excess capacity. For the off-site market, this is a new supply channel to track.

What this means for Developers

Plan for November. Treat the six-month gap as planning time, not a buffer. Baseline ecological surveys have seasonal windows. Unit procurement at scales takes months to arrange. Ecologist engagement, metric calculation, BNG boundary mapping and habitat management planning all need to feed into the application rather than being retrofitted once the deadline arrives. Applications submitted in November 2026 are already being designed now.

Off-site is a legitimate first-instance strategy, not a fallback. The regulatory guidance no longer pushes NSIP developers to exhaust on-site before looking off-site. Strategic off-site delivery is a valid Day One route and a procurement decision best made early, not left until late-stage DCO submission.

Cross-LPA procurement just got simpler. For linear NSIPs, the removal of the spatial risk multiplier penalty across LPAs is a significant practical shift. A single habitat bank can serve a project across multiple administrative boundaries without penalty (with the exception of water course units which must remain catchment-specific).

Temporary land is manageable. The five-year reinstatement window for low-distinctiveness habitats, combined with the clarification that habitats reinstated within the allowed timeframe can be treated as retained rather than secured as long-term BNG delivery, resolves the main operational concern about temporary NSIP impacts. 10% still applies, but it can be delivered through the off-site market rather than through physically impractical on-site commitments.

What this means for Landowners and Habitat Bank Operators

The demand signal is real. The NSIP-driven demand curve will build through 2027 and into the latter part of the decade, rather than arriving as a sudden surge at go-live. Landowners planning around NSIP demand should think in terms of multi-year portfolio positioning, not short-term windfall. With the gain statements now laid before Parliament, developers and infrastructure promoters have greater certainty around how the regime will be applied, allowing BNG requirements to be factored into project planning with more confidence.

Strategic geography becomes more valuable. Because NSIPs can now procure across any LPA or NCA within their BNG boundary without a spatial risk multiplier penalty, habitat banks positioned along major infrastructure corridors become particularly attractive to large-volume buyers.

Habitat diversity matters more. NSIP baselines capture a broad range of habitat types, and the 10% objective must be met separately for each unit type - area, hedgerow, and watercourse. Habitat banks offering a varied habitat mix are better positioned to serve the full spectrum of NSIP requirements than single-habitat sites. Watercourse units in catchments hosting major infrastructure projects are a specific opportunity, given the retained catchment constraint.

Government has explicitly validated private off-site supply. The government response makes clear that private off-site provision is expected to play a central role in meeting NSIP demand. This is the clearest signal to date the private habitat banks - rather than statutory credits or bespoke developer-led solutions - are expected to be the primary route through which NSIP BNG is delivered. That is a commercial endorsement of the business model, not simply a regulatory acknowledgement.

For landowners earlier in the journey, the consultancy route - assessing whether a site is suitable for a habitat bank, modelling likely unit output, and planning registration - remains the most efficient way to understand the commercial opportunity before committing. ILM’s BNG Sites Directory provides a practical reference point for what registered habitat banks look like in terms of habitat mix, scale and positioning.

The Bigger Picture

The final rules should be read alongside the parallel reforms Defra announced for small, medium and brownfield BNG, and the wider direction of travel on Local Nature Recovery Strategies, the Nature Restoration Fund, and statutory biodiversity metric updates.

Taken together, these changes point to a maturing BNG market in which the off-site supply of biodiversity units is an increasingly central piece of infrastructure in its own right. NSIPs are the largest per-project demand category being layered onto this system, and the way Defra has structured the rules suggests a deliberate intent to channel that demand into the existing off-site market rather than building a parallel regime.

For developers, the practical consequence is that early engagement with off-site providers is no longer a late-stage procurement task. Developers who approach BNG on the same way they approach land strategy, early, coordinated and commercially structured, will be better placed to avoid delays later in the DCO process.

For landowners, it confirms that the habitat bank model is the primary route through which major infrastructure will discharge its biodiversity obligations, and that strategic positioning now will serve demand for years to come.

The rules are published. The date is set. Time to secure a strategy that will stand up to it.

How do these changes affect your projects?

Whether you're navigating BNG compliance on a development pipeline or exploring the potential of your land as a habitat bank, our team can help you understand what these changes mean in practice.

Sources

• Defra consultation outcome: BNG for NSIPs (published 15 April 2026)

• Summary of responses and government response (updated 15 April 2026)