BNG for Nationally Significant Infrastructure Projects

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
• On 15 April 2026, Defra published the consultation response and confirmed the start date as 2 November 2026
• Secondary legislation — The Infrastructure Planning (Biodiversity Net Gain) Regulations 2026 — and updated biodiversity gain statements aligned with each National Policy Statement sector were laid before Parliament in May 2026: a preparatory legislative step, not the BNG go-live date

How NSIP BNG differs from standard BNG

While the core principles are the same (10% uplift, 30-year securing, statutory metric), the Regulations confirm several modifications to the standard planning BNG regime, recognising the unique characteristics of NSIPs:

What was confirmed on 15 April 2026

When Defra published its consultation response on 15 April 2026, it confirmed the following details of the NSIP BNG regime:

• Uniform 10% requirement across all NSIP sectors — no sector-specific exemptions or tiered targets.
• Targeted boundaries — BNG is assessed only against habitats negatively affected (temporarily or permanently) by the project, and habitats within the order limits used to contribute towards BNG. Unaffected habitats inside the red line are excluded from the baseline calculation.
• Flexible delivery — on-site and off-site routes have equal primary status; statutory credits remain a last resort. Off-site units can be sourced from any LPA, NCA or Marine Plan Area that the NSIP BNG boundary falls within, with no spatial risk multiplier penalty.
• Significant vs non-significant habitats — habitats counted towards the BNG score that are new or enhanced are "significant" and require 30-year management secured through a DCO requirement, planning obligation or conservation covenant. Habitats temporarily impacted and reinstated to their pre-development state are "non-significant" — they can be counted but do not need to be legally secured.
• Biodiversity gain plan required alongside the DCO application, identifying the role of suitably qualified ecologists and including the completed metric calculation.

The secondary legislation — The Infrastructure Planning (Biodiversity Net Gain) Regulations 2026 — and updated biodiversity gain statements aligned with National Policy Statements were laid before Parliament in May 2026, completing the preparatory legislative groundwork ahead of go-live. Further operational guidance is expected from Defra ahead of the 2 November 2026 go-live.

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 Regulations confirm 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 for large linear schemes.

The targeted boundaries approach (under which only habitats negatively affected by the project count towards the baseline) provides some relief, but promoters should work with ecologists early to understand the practical extent of their baseline calculation.

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 Regulations allow 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 legislative groundwork is now in place. Here is where things stand ahead of the 2 November 2026 go-live:

• 15 April 2026 ✓ Complete: Defra published its full consultation response, confirming the regime design and the 2 November 2026 go-live date
• May 2026 ✓ Complete: The Infrastructure Planning (Biodiversity Net Gain) Regulations 2026 laid before Parliament, together with updated biodiversity gain statements aligned with the relevant National Policy Statements
• Ahead of 2 November 2026: Further operational guidance to be published by Defra
• From 2 November 2026: All new DCO applications must include a biodiversity gain plan and achieve 10% BNG

For the broader picture of all 2026 changes, see our 2026 reforms guide.