BNG for energy and infrastructure NSIPs: what does the August 2026 operational guidance mean in practice?

The August 2026 guidance on BNG for NSIPs (here) is lengthy, and with the volume of recent biodiversity net gain (BNG) announcements, we wouldn't blame anyone for being tempted to paste the lot into [insert preferred AI tool here] and hope for the best. We've tried to save you the trouble (and the hallucinations) by distilling the guidance into a practical, FAQ-style summary of the key BNG issues that are likely to arise through the consenting phase of a NSIP, with a list at the end of what should project teams do now; consider this your cheat sheet to help you understand the BNG framework for NSIPs. 

Here are the headlines:

• From 2 November 2026, mandatory BNG will apply to DCO applications made on or after that date, requiring at least 10% net gain in biodiversity.
• The August guidance confirms that on-site habitat creation and off-site unit procurement can be developed in parallel from the outset; statutory credits remain a last resort.
• For coastal projects, mandatory BNG applies as far as mean low water, including intertidal habitat, but not beyond it into the marine environment.
• For cross-border NSIPs, only habitats in England count towards the mandatory baseline, boundary plan, metric calculation and delivery of mandatory gains.
• Temporary impacts, route uncertainty, existing gain sites and post-consent phasing now need to be managed as delivery risks, not left as technical metric points.
• Developers should build pre-operation milestones for securing biodiversity units, habitat management and monitoring plan (HMMP) obligations and discharging authority engagement into their programmes now.

For our June 2026 article "BNG for energy and infrastructure NSIPs: Navigating the new guidance ahead of 2 November 2026" see here.

Can developers pursue on-site and off-site BNG delivery in parallel?

One of the most useful clarifications is that developers do not need to exhaust all on-site opportunities before considering off-site provision. On-site habitat creation and off-site unit procurement can be developed in parallel from the outset. For large linear schemes, that reflects practical reality: the need for some off-site provision may be apparent long before the detailed design is fixed.

What does the guidance say about cross-border projects?

For cross-border NSIPs, the mandatory BNG calculation must be confined to England. The baseline, boundary plan and statutory metric should include only habitats in England, and any enhancements intended to satisfy the mandatory obligation must also be delivered in England. Project-wide biodiversity strategies can still cover habitats outside England, but those calculations need to be kept separate.

What does the guidance mean for coastal and marine-adjacent projects?

For coastal and marine-adjacent projects, mandatory NSIP BNG extends to the mean low-water mark and includes intertidal habitat. Habitat beyond mean low water remains outside the mandatory NSIP BNG requirement. Ports, offshore wind, coastal energy and other marine-adjacent projects should therefore check BNG boundary plans and metric calculations carefully so that intertidal habitat is captured and marine habitat beyond mean low water is not included unnecessarily.

How should developers approach design uncertainty and realistic worst-case assessments?

The guidance gives useful practical detail on how developers should deal with design flexibility and route uncertainty. The core principle is a realistic worst-case assessment, rather than an artificially conservative calculation based on every habitat that could theoretically be affected within the widest order limits.

For linear schemes, that means focusing on the realistic maximum construction width and ancillary works areas, not simply assuming loss across the full width of the limits of deviation.

The guidance illustrates this approach through worked route scenarios involving different habitat values. These examples reinforce the need to distinguish between a preferred or most likely design and alternatives that remain realistically available. The outline gain plan should record the assumptions adopted and explain how the BNG position would be addressed if a different route or design were ultimately selected.

What is the position on temporary habitat impacts?

Temporary impacts also need active programme management. Low and very low distinctiveness habitat can be treated as retained if restored to its original type and condition within five years of impact; medium distinctiveness habitat can be treated as retained if restored within two years. Treating qualifying habitat as retained can reduce the number of replacement biodiversity units required, subject to the habitat being reinstated within the applicable period. If reinstatement is not achieved in time, the metric and relevant updated or phase gain plans must be amended.

What do the baseline-date provisions mean in practice?

Current ecological conditions will not always be the right baseline. Where habitat value has been reduced before submission, including through unauthorised degradation or activity under an existing permission or DCO, an earlier baseline date may need to be used. Degradation occurring before 30 January 2020 does not need to be accounted for. Developers should review site history, pre-application works and existing consents early, and raise any baseline-date issue with the Planning Inspectorate during pre-application engagement. The guidance states that not only does the Secretary of State need to agree on an earlier baseline, but that the examining authority (the inspectors reviewing an application) also needs to agree on the earlier baseline during the consent phase. No further guidance is given about what happens if for example the Secretary of State and the examining authority disagree with each other, but we assume the examining authority will be the “face” of those discussions during the examination period and will ultimately defer to the Secretary of State.

What happens if an NSIP affects an existing biodiversity gain site?

Developers can no longer assume that apparently undeveloped land is free of biodiversity obligations. Existing gain sites may already be delivering units allocated to another project and may already be subject to legal agreements or conservation covenants.

The guidance explains that such circumstances may affect baseline calculations and may require amendment of existing arrangements or other consequential measures.

Checking for existing gain sites should now form part of standard project due diligence, particularly for infrastructure projects involving extensive corridors as carrying out searches on large extents of land will take some time. 

A local land charges search should reveal any such legal agreements or conservation covenants. The Biodiversity Gain Site Register can be searched to check if a site is already registered, but you would need a number of identifiers such as a grid reference or planning reference number to find sites. As at the date of publication of this blog the Site Register doesn’t have the functionality to carry out a geospatial search to identify affected land, however, it appears there are free-to-access third-party websites which show BNG maps; this is a good starting point to locate any existing sites near a proposed development.

What does a DCO application need to include?

A DCO application needs to include:

• an outline biodiversity gain plan;
• draft DCO requirements relevant to BNG; and
• a HMMP (if on-site gains are secured through DCO requirements). 

What must the outline biodiversity gain plan address?

The outline gain plan should explain the delivery strategy, identify the habitats included in and excluded from the baseline, justify realistic worst-case assumptions, set out how outstanding gains will be secured, and demonstrate appropriate ecological input. It also needs to include the metric calculation and the BNG boundary plan. 

What should the DCO requirements secure?

The DCO requirements should secure: 

BNG objective

1. submission of updated or phase gain plans after consent; 
2. delivery of BNG in accordance with approved gain plans; and
3. calculation and securing of any remaining biodiversity unit shortfall before the project, or relevant phase, begins operating. 

On-site gains (if included in the DCO application)

1. submit a HMMP for approval alongside the updated biodiversity gain plan before commencement;
2. manage and maintain any significant on-site gains for at least 30 years from completion of the habitat enhancement works;
3. seek reapproval of an updated HMMP if the significant on-site gains allocated to the development change; and
4. submit monitoring reports to the discharging authority. 

What is the difference between the outline biodiversity gain plan and the HMMP?

The outline gain plan is the strategic document demonstrating how the project will meet its BNG objective. The HMMP is the operational document setting out how the habitats relied on in that strategy will be created, enhanced, managed, monitored and maintained over the required period.

Who should discharge the BNG requirements?

Developers must also identify the proposed discharging authority in the DCO application. The appropriate authority may be the host LPA, a lead LPA, or the Secretary of State, depending on the scale and complexity of the project. This should be discussed early with the Planning Inspectorate and relevant local authorities, and developers should consider whether an appeals mechanism is needed if approval is refused or delayed.

What should developers consider when procuring off-site biodiversity units?

Off-site procurement is now a programme-critical workstream. Some NSIPs may need large numbers of units or habitat types that are not readily available, so early engagement with landowners, habitat banks and unit providers will be important. The DCO application should give enough assurance that required off-site units are likely to be available, whether through reserved units, landowner arrangements or agreements to create units.

How do the spatial-risk multipliers affect off-site provision?

The spatial risk multiplier adjusts the value of off-site compensation depending on its location relative to the project site. This encourages developers to prioritise habitat enhancements on-site or nearby off-site, because the cost of off-site compensation increases the further it is from the project site. Area and hedgerow units are assessed by LPA and Natural Character Area boundaries. intertidal units by Marine Plan Area boundaries, and watercourse units by waterbody or catchment boundaries. Sourcing units outside the relevant area can increase the number of units needed.

Developments that cover large areas and span multiple LPA boundaries (such as projects with extensive corridors) will be well placed to avoid these penalties and keep the full value of off-site gains because the multiplier is based on the entire BNG boundary. This means that off-site gains can be sourced from any LPA area through which the BNG boundary passes without attracting the spatial risk penalty.

DEFRA indicated in a blog dated 27 August 2026 that it will be making some changes to the way spatial risk is assessed for area habitats by using Local Nature Recovery Strategy areas only. Further details are anticipated "in due course" but for now this seems to indicate a change in a positive direction as it would potentially simplify and reduce the penalty burden.

When can statutory biodiversity credits be used?

Statutory biodiversity credits remain a last resort. If they may be needed, the application should explain why on-site and off-site options cannot meet the requirement and should justify reliance on credits. Any outstanding shortfall must still be secured before the project or phase begins operating.

What can developers do with excess on-site gains?

Developers may also generate excess on-site gains. Those gains can be retained for the project, allocated to another development or sold into the off-site market, provided this is consistent with the wider mitigation strategy. Land not required to deliver BNG may still be needed for other mitigation, so developers should consider competing land requirements before allocating or selling excess gains. The relevant gain plans and legal agreements need to make clear how they are being used and secured.

How does the timing of habitat delivery affect the metric outcome?

The timing of habitat creation can affect the metric outcome. Early creation can increase the biodiversity units generated and affect the quantity of units that need to be procured. Habitat delivery should therefore be programmed alongside engineering and construction activity rather than treated solely as a post-consent environmental workstream.

How does BNG operate after consent and across project phases?

After consent, developers must submit updated or phased gain plans to the discharging authority and deliver BNG in accordance with the approved plans. Recalculation may be required where design changes increase habitat impacts, reduce on-site provision or alter the value of affected habitat. Updated metric calculations and HMMP material should be clearly version-controlled.

When must any outstanding biodiversity units be secured?

The 10% BNG requirement applies to the development as a whole, not necessarily each phase. Any unit shortfall must be secured before the relevant phase operates, and the final phase cannot begin operation until the project-wide requirement is secured.

If impacts are uncertain before commencement, the outline gain plan should specify what will be secured at each stage, how the final requirement will be recalculated, and how any residual shortfall will be addressed.

What management and monitoring obligations apply?

Management and monitoring obligations also need to be planned early. HMMPs must be capable of supporting the commitments made in the gain plans, and management obligations will generally run for at least 30 years from completion of the relevant habitat creation or enhancement works. For projects operating for longer than 30 years, habitats should continue to be maintained for at least the full operating period.

What sector-specific and technical issues should developers consider?

The guidance also flags a number of sector-specific points. Irreplaceable habitats remain subject to bespoke treatment rather than ordinary metric-based replacement. Watercourse units use waterbody and catchment geography for spatial-risk purposes. For projects near aerodromes, BNG habitat design may need to address bird strike risk and early engagement with safeguarding bodies.

How can habitat measures delivered under other environmental regimes count towards BNG?

The guidance also provides helpful clarification on the interaction between BNG and habitat measures required under other environmental regimes. In some cases, habitat mitigation, compensation or enhancement delivered within protected sites or under related regimes, including nutrient neutrality, Habitats Regulations measures, River Basin Management Plan enhancements and SuDS, may be included in the BNG calculation. Some measures may count in full, while others may only count up to no net loss, thereby reducing the overall number of units needed to achieve the gain. 

What should project teams do now?

The August guidance does not fundamentally change the mandatory NSIP BNG framework, but it does make clear how Government expects that framework to operate in practice. Developers with live or upcoming DCO applications should now:

1. progress on-site and off-site delivery strategies in parallel, including considering the location and proximity of any proposed off-site gains given the potential application of the spatial risk multiplier penalty);
2. check coastal, intertidal and cross-border assumptions in survey scopes, baselines and metric calculations;
3. calibrate baseline surveys and outline gain plan assumptions to the realistic worst-case construction scenario;
4. screen order limits and corridors for existing registered gain sites or legally secured biodiversity obligations;
5. review temporary impact assumptions against construction programmes and reinstatement deadlines;
6. engage early with the Planning Inspectorate on discharging authority, phasing, baseline dates and DCO requirements;
7. build pre-operation milestones for securing biodiversity units into procurement and delivery programmes; and
8. prepare a HMMP, monitoring and long-term land management arrangements early.

We would be happy to discuss any aspect of this in more detail, and how this could affect your projects. Please contact us using the contact details below.