Frequently asked questions.
General FAQs
What is Biodiversity Net Gain and how will this affect UK developers?
Biodiversity Net Gain (BNG) is a mandatory requirement under the Environment Act. It requires English developers to demonstrate a measurable increase in biodiversity resulting from new development. This means undertaking biodiversity assessments, implementing habitat enhancements, and providing evidence of net gain to secure planning permission.
Where a developer cannot deliver BNG wholly on-site, they can meet the requirement by purchasing off-site Biodiversity Units, which provide a flexible and cost-effective route to compliance.
What is the DEFRA Metric? How is it used to calculate BNG Units?
The DEFRA Biodiversity Metric is a habitat-based tool used to calculate BNG in England. It provides a proxy biodiversity value based on habitat type, distinctiveness, condition, and location. The metric is used to assess biodiversity losses and proposed gains for a development site.
You can find official guidance here: DEFRA Biodiversity Metric Guidance
What is the Biodiversity Metric?
The Biodiversity Metric is central to demonstrating BNG. Developed by Natural England, it allows planners, ecologists, and developers to assess the biodiversity value of land before and after development. The latest version, known as the Mandatory Biodiversity Metric, must be used for all BNG calculations.
How many BNG Units will I need?
The number of units required depends on your site’s size, location, and existing ecological value. An ecologist will use the DEFRA Metric to calculate this. You may be able to deliver some or all of your BNG on-site, but any shortfall must be addressed through off-site units or statutory biodiversity credits.
What is on-site vs. off-site BNG?
• On-site includes land within the red-line boundary of a development application.
• Off-site is any land outside of this boundary, regardless of ownership.
Note: Land within the blue-line boundary is not considered on-site.
How long must off-site BNG be maintained?
All off-site biodiversity gains must be legally secured for a minimum of 30 years, and registered before they can be counted toward BNG. This must be done via a planning obligation or a conservation covenant.
What is the Spatial Multiplier in BNG?
The DEFRA Metric includes a Spatial Risk Multiplier, which reduces the value of habitat enhancements made farther from the development site. This encourages delivery of BNG as close to the development as possible.
If on-site delivery is not feasible, developers can secure off-site units that meet the criteria of the national Biodiversity Gain Site Register. If neither of these options are possible, statutory biodiversity credits from the government may be used as a last resort.
What is a Biodiversity Gain Plan?
A Biodiversity Gain Plan (BGP) is submitted after planning permission is granted. It outlines how BNG will be achieved — including baseline biodiversity, post-development enhancements, and off-site purchases (with DEFRA register reference numbers if applicable).
This plan must be approved by the Local Planning Authority before development can begin.
When does a BNG Unit Option or Purchase need to be included in a planning application?
BNG is typically secured via a Section 106 agreement. To obtain planning permission, developers must demonstrate a compliant BNG solution.
Once planning is granted, the developer must submit a Biodiversity Gain Plan. Off-site units are formally retired from the DEFRA Register at this stage, and this must be completed before development begins.
What is the process for buying BNG Units through Biodiversity Units UK?
The buying process is simple and structured:
1. Submit project info – Provide your DEFRA Metric, site address, and planning timeline.
2. Receive BNG options – We’ll search the market and present tailored solutions.
3. Select your preferred option – We’ll issue a Letter of Support and Solution Methodology for your planning application.
4. Reserve your units – Pay a 10% deposit to reserve units for up to 12 months.
5. Complete your purchase – Pay the balance, and your units will be registered on the DEFRA Register.
6. Notify your planning officer – Submit your documents to the Local Planning Authority as evidence of BNG compliance.
What documents will I receive during the BNG Unit purchase process?
From Biodiversity Units UK, you will receive:
✅ Letter of Support
✅ Solution Methodology
✅ Letter of Reservation
✅ Option Agreement (or Purchase Agreement)
✅ Updated DEFRA Metric
✅ Biodiversity Gain Site Registration Number
✅ Supplier’s Habitat Management Plan
✅ Support for Section 7 of your Biodiversity Gain Plan
From your ecological consultant or project team, you should prepare:
✅ Original DEFRA Metric
✅ Ecologist’s Report
✅ Your Biodiversity Gain Plan (including other project information)
✅ On-site Habitat Management and Monitoring Plan (if applicable)
What are the key components of mandatory BNG?
• Minimum 10% net gain in biodiversity
• Calculated using the DEFRA Biodiversity Metric
• Must be secured for 30 years via legal agreement
• Delivered on-site, off-site, or through statutory biodiversity credits
• Biodiversity Gain Plan must be submitted and approved
• Sites delivering BNG must be recorded on the Biodiversity Gain Site Register
• Applies to most planning applications, except certain exemptions
• Retains the mitigation hierarchy: avoid, mitigate, compensate
When did BNG become mandatory? What about small sites?
Mandatory BNG began on 12 February 2024 for most developments. For small sites, the requirement started in April 2024, giving smaller developers and planning authorities additional time to adapt.
Small sites are defined as:
• Residential: 1–9 dwellings on a site under 1 hectare
• Non-residential: Less than 1,000 m² of floor space or a site under 1 hectare
Is BNG mandatory outside of England?
No. BNG under the Environment Act currently applies only in England. The provisions are set out in Schedule 14 of the Act. Other nations, such as Scotland and Wales, are developing their own approaches to biodiversity enhancement.
What is the national biodiversity credits scheme?
This is a government-run scheme where developers can purchase statutory biodiversity credits when BNG cannot be delivered on-site or off-site. These credits are priced higher than market rates to encourage natural market delivery first. Revenue from credit sales is reinvested into habitat creation. Natural England manages the scheme and is developing a user-friendly digital platform for transactions.
FAQs for Property Developers
Understanding BNG
BNG is an approach to development that leaves habitats for wildlife in a measurably better state than before. Developers achieve this by retaining, improving or creating habitats, with the change measured in biodiversity units.
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What is Biodiversity Net Gain (BNG)?
Most developments requiring planning permission in England must meet mandatory BNG requirements unless an exemption or transitional arrangement applies. Your application date, development type and site characteristics determine whether your scheme is covered.
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Does BNG apply to my development?
The statutory minimum is a 10% increase in biodiversity value compared with the site’s baseline. This is measured in BNG units, rather than simply the amount of green space. Check whether applicable local planning policy requires a higher percentage. Understanding BNG.
How much biodiversity gain does my development need to achieve?
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Which developments are exempt from BNG?
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Exemptions include householder applications, qualifying developments affecting very small amounts of habitat, certain temporary developments and development under permitted development rights. For applications made from Aug 6, 2026, sites of 0.2 hectares or less can also qualify. Some exemptions do not apply where priority habitat is affected, so eligibility needs checking carefully.
Does BNG apply to small sites and brownfield developments?
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It can. Small developments are not automatically exempt, although qualifying applications on sites of 0.2 hectares or less may be. Brownfield status alone does not provide an exemption, as previously developed land can support valuable habitats. Government exemption guidance.
Does the same mandatory BNG requirement apply across the UK?
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No. The mandatory framework described here applies to England. Developments in Scotland, Wales and Northern Ireland must follow their respective planning policies and environmental requirements. Scope of England’s BNG framework.
Assessments and Planning
Start during site selection and feasibility, before fixing your layout. Early assessment helps identify valuable habitats, compare design options and budget for any off-site units required. Planning guidance.
When should I start considering BNG?
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Do I need an ecologist to assess my site?
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For most schemes, a suitably competent ecologist should survey the habitats and complete the assessment. Eligible developments using the Small Sites Metric can use another competent person with the necessary knowledge of the site and its habitats.
Where can I find a BNG-experienced ecologist?
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Our Ecologists for BNG Directory is a free regional directory designed to help developers find vetted ecologists with BNG experience. Your ecologist should advise on the survey, metric and the units your project actually needs.
How is my site’s existing biodiversity value measured?
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A habitat survey records the habitats within the development’s red line boundary. Their type, area or length, condition and strategic significance are entered into the relevant metric to calculate the baseline biodiversity units.
What is the statutory biodiversity metric, and when can I use the Small Sites Metric?
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The statutory biodiversity metric is the official method for calculating habitat losses and gains. The Small Sites Metric is a simplified tool for eligible minor developments, subject to additional ecological restrictions. Being a small development does not automatically make it suitable. Metric guidance.
For a scheme subject to BNG, the minimum information includes the baseline biodiversity value, completed metric calculation and a habitat plan. You must also address relevant habitat degradation and identify irreplaceable habitats. Check the council’s validation requirements for additional information.
What BNG information must I submit with my planning application?
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It explains how the approved development will achieve its BNG requirement, including on-site gains, registered off-site gains and any statutory credits. It must be formally approved after planning permission is granted and before development starts or before occupation, depending on the wording of your condition.
What is a Biodiversity Gain Plan, and when does it need approval?
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For development subject to the biodiversity gain condition, you must obtain approval of the Biodiversity Gain Plan before commencing development. Phased schemes have additional requirements for overall and phase plans.
Can I start construction before my BNG requirements are approved?
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BNG operates alongside other ecological duties. Achieving the required gain does not remove obligations relating to protected species, designated sites or necessary licences. These must also be addressed in your assessment and design. Planning and approval guidance.
How does BNG relate to protected species and other ecological requirements?
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Delivering biodiversity gain
Can I meet my BNG requirements entirely within my development site?
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Yes, if retaining, enhancing and creating habitats within the red line boundary produces sufficient units and meets the metric’s rules. Your proposals must also be practical to deliver and maintain.
Can landscaping, green roofs and sustainable drainage features contribute to BNG?
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Yes, where they provide habitats recognised by the metric. Their contribution depends on their design, extent and achievable condition. Standard ornamental landscaping may contribute less than carefully designed wildlife habitats. On-site guidance.
What happens if I cannot achieve enough biodiversity gain on-site?
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You can use eligible off-site gains to address the shortfall. Most developments must follow the biodiversity gain hierarchy, prioritising avoidance and on-site options. Since Aug 6, 2026, non-exempt minor developments can consider on-site and off-site delivery together. Statutory credits remain a fallback option. Delivery options.
What is on-site BNG? What qualifies?
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On-site BNG is biodiversity retained, enhanced or created within the red line boundary of the development. Habitats only count if they are recognised and entered correctly in the statutory biodiversity metric. This can include retained habitats, new or enhanced grassland, hedgerows, trees, ponds, green roofs and other qualifying habitats. Significant on-site enhancements must normally be secured and maintained for at least 30 years. Land outside the red line is off-site, even if the developer owns it. Government on-site BNG guidance.
Think of it as the order in which BNG options should be considered. For major development, first avoid or reduce impacts to medium, high and very high distinctiveness habitats; then prioritise enhancing existing on-site habitat, creating new on-site habitat, using registered off-site gains, and finally statutory biodiversity credits. Under the current rules for qualifying minor development, on-site and off-site delivery can be considered at the same level of preference; statutory credits still come last. Government BNG guidance.
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What is the biodiversity gain hierarchy?
How will the biodiversity gain hierarchy affect my project?
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For a major scheme, it can influence layout, design, cost and the evidence you need to show the LPA. If valuable habitat can reasonably be retained, you should not assume you can simply remove it and buy units elsewhere. Test the hierarchy early with your ecologist, keep a clear record of the options considered, and identify any likely off-site shortfall before the design is fixed. Minor developments now have more flexibility to go off-site earlier. Government BNG guidance.
What is the Spatial Risk Multiplier?
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The Spatial Risk Multiplier (SRM) reduces the value of off-site gains that are farther from the development. For area habitats and hedgerows, units within the same Local Planning Authority or National Character Area score 1.0; units in a neighbouring LPA or NCA score 0.75; units further away score 0.5. So a more distant unit may mean you need to buy more units to achieve the same result. Watercourses use catchment boundaries instead. Statutory biodiversity metric user guide.
Can I use other land I own to deliver BNG?
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Yes. Land outside your planning application’s red line boundary counts as off-site, even if you own it or it sits within a blue line boundary. Gains on that land must meet the off-site legal, registration and allocation requirements.
What are off-site biodiversity units, and how do I buy them?
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They represent habitat improvements outside your development boundary. You can buy them from landowners, habitat banks or through brokers. The gain site must be registered and the units allocated to your development before your Biodiversity Gain Plan can be approved. Biodiversity Units UK can source supplier options from your metric and introduce you to the selected provider.
Do off-site biodiversity units need to be located near my development?
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They can come from elsewhere in England, but location affects their value to your scheme. The metric’s spatial risk multiplier can mean that more distant gains require additional units. Off-site guidance.
What is the difference between biodiversity units and statutory biodiversity credits?
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Off-site units are purchased through the private market and linked to specific habitat improvements. Statutory credits are purchased from the government where the applicable requirements are met. They are generally a last resort, with prices designed to encourage delivery through other routes. Statutory credit guidance.
Buying and securing biodiversity units
How many biodiversity units will I need to buy?
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Your metric calculation identifies the shortfall remaining after accounting for habitat losses and on-site gains. The habitat types and location of the proposed off-site gains also affect your purchase requirement. There is no fixed number of units per hectare. Metric guidance.
How can I check that off-site units are suitable for my development?
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Ask your ecologist to check the habitat type, quantity, location and metric trading rules. Confirm that the gains are legally secured, registered and available for allocation to your scheme. A purchase receipt alone is insufficient. When sourcing through Biodiversity Units UK, share the proposed options with your ecologist so technical suitability is confirmed before purchase.
Do I need to buy biodiversity units before submitting my planning application?
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No. You can purchase units before or after applying for permission however the units cannot be allocated without a planning decision notice. Your application should nevertheless demonstrate a credible BNG approach. Off-site gains must be registered and allocated before your Biodiversity Gain Plan can be approved.
What documents should I receive when buying off-site biodiversity units?
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Obtain a purchase agreement identifying the units, price and allocation responsibilities, alongside the gain site registration number and evidence of allocation. Request supporting habitat and management information needed for your Biodiversity Gain Plan. Document names and packages vary between suppliers. If you choose BNG Certainty, Biodiversity Units UK can coordinate the documentation with your project team. Agree the scope and who will obtain each item before instructing the service. Purchase and allocation guidance.
Some suppliers offer reservations or option agreements. Check the reservation period, deposit, refund terms and what happens if permission is refused or your requirements change. There is no universal deposit percentage or reservation period. Biodiversity Units UK can help identify reservation options with suppliers; the terms should be confirmed for your chosen supply.
Can I reserve biodiversity units while waiting for planning permission?
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What information should I provide to obtain a quote for biodiversity units?
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Provide your completed biodiversity metric, development location and anticipated planning and construction timetable. Explain whether the design is final or your requirements may change. This helps suppliers identify suitable units and availability. You can share this information with Biodiversity Units UK as a single sourcing brief, with a named contact coordinating supplier options. Biodiversity Units UK service information.
How can Biodiversity Units UK help me find suitable units?
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Share your completed metric, site location and timetable. Biodiversity Units UK searches across suppliers and presents up to four supply options, depending on availability and fit. You have a named contact to coordinate the enquiry. Your ecologist should confirm that the chosen package meets the development’s requirements.
Is there a fee for Biodiversity Units UK to source units?
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There is no client fee for the BNG Core sourcing service. Suppliers pay us a commission under its matched-pricing model. Optional BNG Certainty support carries a separate fee. Confirm the unit price, included services and any additional charges in the proposal.
What is the difference between BNG Core and BNG Certainty?
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BNG Core covers sourcing supplier options and introducing you to the selected supplier. You and your advisers then manage the transaction and compliance process. BNG Certainty adds paid support with further negotiation, documentation, Biodiversity Gain Plan preparation, project team and council liaison, contract coordination and condition discharge. Agree the scope and fee before instruction.
Does Biodiversity Units UK own the habitats supplying the units?
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No. Biodiversity Units UK acts as a marketplace, connecting buyers with habitat banks and other suppliers. The supplier’s legal arrangements secure habitat delivery and management. Check the purchase documents to understand the contracting parties and their responsibilities.
Do on-site biodiversity gains need to be registered on the national register?
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No. The national Biodiversity Gain Sites Register is for off-site gains. On-site gains are addressed through your approved Biodiversity Gain Plan, with significant enhancements secured through appropriate conditions or legal agreements. On-site guidance.
How long does it take to buy and transact on off-site BNG units?
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The commercial purchase can be completed in a few days where your metric is clear, suitable units are available, the gain site is ready and the buyer and supplier can move quickly. The important caveat is that buying units is only part of the compliance process. Units cannot be formally allocated to a development until the relevant planning decision exists. Natural England allows up to six weeks to determine an allocation application, and the LPA normally has eight weeks to determine the Biodiversity Gain Plan. Rare habitats, legal issues, design changes or a gain site that still needs registration can add time. Natural England allocation guidance. Biodiversity Gain Plan guidance.
Costs and timescales
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How much does BNG cost, and what affects the price?
Costs depend on the habitat baseline, proposed losses, on-site opportunities and any off-site shortfall. Private unit prices are negotiated with suppliers; government credit prices are published separately. Biodiversity Units UK’s BNG Price Calculator can support early budgeting, while its BNG Pricing Report provides market context. A project-specific quotation is still needed. Offsite purchases and statutory credit prices.
What should I include in my BNG budget?
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Allow for surveys, calculations, design advice, habitat works and unit purchases. Include relevant legal, registration and council fees, plus long-term management, monitoring and reporting. Budgeting only for planting or purchasing units can miss ongoing commitments. On-site delivery guidance.
How long do BNG assessments, unit purchases and approvals take?
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Timescales depend on survey needs, design complexity, unit availability and legal arrangements. The normal determination period for a Biodiversity Gain Plan is eight weeks, unless a different period is agreed. Allow time for queries and revisions.
How can I reduce BNG costs and avoid planning delays?
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Assess habitats early, retain valuable features and compare layouts before committing to a design. Use realistic habitat targets, establish any unit shortfall promptly and discuss your approach with the council. Where off-site units are needed, Biodiversity Units UK can help compare supply options early, alongside your ecologist and planning adviser. Planning guidance.
Where can I get a quick BNG unit budget for my design or development project?
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Use our free BNG Price Calculator. Upload your statutory biodiversity metric and it gives you a low, medium and high market estimate in seconds, so you can test budgets and design options before going out for live quotes. It is powered by the nationwide pricing dataset behind our quarterly BNG Pricing Report — the only UK-wide BNG price analysis of its kind — which we have published since 2024. Treat the result as an early budget rather than a supplier quote.
What price should I expect to pay for off-site BNG units?
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There is no single market price per BNG unit. Price varies by habitat type and distinctiveness, development and gain-site location, local scarcity, volume and commercial terms. A common grassland unit can therefore price very differently from a scarce watercourse or priority habitat unit. Use our BNG Pricing Report for market benchmarks and the BNG Price Calculator for a project-specific budget range, then get live supplier quotes before committing..
Long-term responsibilities
How long must BNG habitats be maintained?
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Significant on-site enhancements and off-site gains must be secured for at least 30 years. The start date depends on the delivery route and relevant condition or agreement.
Who is responsible for managing and monitoring the habitat banks?
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Responsibilities should be clearly identified in the conditions, legal agreement and habitat management plan. Appointing a contractor does not automatically transfer legal responsibility. For purchased off-site gains, the gain site landowner is responsible under the arrangements securing those gains. Legal agreement guidance.
What legal agreements are needed to secure biodiversity gain?
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Off-site gains require a section 106 planning obligation or conservation covenant. Significant on-site enhancements can be secured through planning conditions, a planning obligation or a conservation covenant, depending on the scheme. Planning guidance.
What happens if the habitats fail to achieve the agreed biodiversity gain?
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Management plans and legal arrangements should address corrective action if habitats miss their targets. Failure to meet secured obligations can lead to enforcement by the council or responsible body. Management and monitoring guidance.
What happens to BNG obligations if I sell the site or completed development?
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Selling does not automatically end the obligations. Conditions and legal agreements can continue to bind the land and subsequent owners. Sale documents should explain ongoing duties and any retained developer liability.
Will I need to update my BNG assessment if my development plans change?
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Potentially. Changes to layout, habitat losses or landscaping can alter your calculations and delivery arrangements. Review revisions with your ecologist and council to establish whether updated calculations, plans or approvals are required. Planning guidance.
FAQs for NSIP Developers
Mandatory BNG applies to qualifying Development Consent Order (DCO) applications submitted on or after Nov 2, 2026. The minimum requirement is 10% biodiversity net gain. Government NSIP guidance.
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When does mandatory BNG apply to NSIPs?
Which BNG rules should I consult for an infrastructure project?
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Start with the biodiversity gain statement relevant to your project’s sector, alongside the applicable National Policy Statement and government guidance. Gain statements set out how projects must calculate, deliver and evidence BNG. A separate statement covers development where no National Policy Statement has effect. Biodiversity gain statements.
The Spatial Risk Multiplier reduces the value of off-site gains that are farther from the project’s impact site. For area habitats and hedgerows, gains within the same Local Planning Authority or National Character Area score 1.0, neighbouring areas score 0.75, and gains further away score 0.5. Watercourses use catchment boundaries. This means location can materially change how many off-site units a large project needs to secure. Government NSIP BNG guidance.
What is the Spatial Risk Multiplier for an NSIP?
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How should an NSIP team budget for off-site BNG units?
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Start with current market benchmarks, but do not rely on one average price per unit. Habitat type, distinctiveness, geography, scarcity and volume can all change the price. Use the BNG Pricing Report for market context, then test the live supplier market against the project’s likely habitat requirements and phasing. For very large or scarce packages, early market testing is especially important.
How long can an NSIP off-site unit transaction take?
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Once a suitable package is agreed, the commercial transaction itself can move quickly. The wider programme is usually longer because large projects may involve procurement, due diligence, phasing, legal agreements and changes to the DCO design. Formal allocation also requires the relevant decision letter and Natural England can take up to six weeks to determine an allocation application. Build the unit strategy into the consent and procurement programme early.
Does mandatory BNG cover offshore and cross-border infrastructure?
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The framework covers the components in England, including the intertidal zone down to the mean low-water mark. It does not cover the marine environment beyond that boundary. Gains counted towards England’s mandatory requirement must be delivered in England. NSIP scope guidance.
How is an NSIP’s biodiversity unit requirement calculated?
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The project’s ecologists use the statutory biodiversity metric to assess the baseline, habitat losses and proposed gains. The resulting shortfall identifies the off-site units required. Habitat type, trading rules, location and delivery timing all influence the final purchase requirement. Statutory metric guidance.
Does the BNG assessment cover everything within the DCO order limits?
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Not necessarily. The baseline includes habitats negatively affected and habitats used to deliver BNG. Unimpacted habitats can be excluded where justified. The BNG boundary therefore needs careful definition and may differ from the order limits. Check the relevant sector statement. Gain statement collection.
Can an NSIP use off-site units without first exhausting on-site delivery?
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Yes. NSIPs can consider on-site and off-site delivery together. This flexibility does not remove the need to avoid and minimise ecological harm. Statutory biodiversity credits remain a last resort. NSIP delivery guidance.
When should an NSIP team start researching unit availability?
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Begin once likely habitat shortfalls emerge. Large projects may need substantial quantities or uncommon habitat types. Early enquiries help suppliers assess future demand and allow the project team to compare availability, costs and procurement options. Biodiversity Units UK can support an early market enquiry based on the project team’s likely requirements.
What information should we provide when requesting unit quotes?
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Provide the latest metric, project location or route, habitat requirements, indicative quantities and consent programme. Explain design uncertainties, likely phasing and when units may be needed. Distinguish an initial market enquiry from a request to reserve or purchase units. For enquiries to Biodiversity Units UK, identify the procurement lead and the project ecologist so commercial and technical questions reach the appropriate person.
Can we source units from several habitat banks or landowners?
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Yes. A procurement strategy can combine suppliers and habitat types. The project ecologist should check the combined solution against the metric, while the procurement team coordinates contracts and allocation evidence. Off-site purchasing guidance.
No. However, the outline gain plan should provide credible evidence that the required units can be secured, such as availability evidence or provider arrangements. The procurement strategy should accommodate design changes. NSIP procurement guidance.
Do we need to buy all units before submitting the DCO application?
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An outline biodiversity gain plan and draft BNG requirements are needed. The outline plan explains the delivery strategy, calculations, uncertainties and proposed arrangements for securing gains. Follow the relevant sector statement for the full evidence requirements. Biodiversity gain statements.
What BNG documents are needed for the DCO application?
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Record assumptions and assess realistic worst-case habitat impacts. Explain how alternative designs could change habitat requirements and how additional gains would be secured. Revisit the metric and procurement package as the design becomes more certain. Example: energy biodiversity gain statement.
How should we account for route changes or design uncertainty?
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Can BNG be delivered through a phased approach?
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Yes. The outline plan must address the whole project, with detailed phase plans where appropriate. The overall gain must still be achieved for the development actually delivered, including where later phases are cancelled. Check the project’s sector statement and DCO requirements. Example: energy gain statement.
Must every unit be secured before construction starts?
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Secure as many as reasonably possible before commencement. An agreed schedule may permit some outstanding units to be secured later where justified. All remaining gains must be secured before the relevant project or phase starts operating. Follow the approved plans and DCO requirements. NSIP securing requirements.
What should we check before committing to an off-site purchase?
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Check habitat compatibility, quantities after relevant multipliers, delivery assumptions, legal security, registration status and allocation arrangements. Commercial checks should cover payment, cancellation, changes in demand and responsibility for completing allocation. Metric tools and allocation guidance.
How long must NSIP biodiversity gains be maintained?
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Created or enhanced on-site habitats contributing to BNG, and off-site gains, must be secured for at least 30 years. Agreements and DCO requirements should identify management, monitoring and reporting responsibilities. Legal agreement guidance.
Does achieving BNG replace other environmental assessments or compensation?
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No. BNG operates alongside environmental assessment, protected species duties and designated-site requirements. Habitat works required for other purposes may contribute only where the applicable rules allow; avoid assuming all environmental mitigation counts towards BNG. NSIP gain statements.
How can Biodiversity Units UK support an NSIP procurement team?
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Biodiversity Units UK can help research supplier options against the team’s habitat requirements, location and delivery programme. Agree the scope for reservations, transaction coordination and supporting evidence. The project’s ecologists, planning advisers and legal team remain responsible for their appointed roles; confirm any DCO-specific support before instruction.
FAQs for Ecologists
Start exploring availability once your assessment identifies a likely shortfall. Early enquiries help establish costs and identify scarce habitat types. Confirm the final requirement against the latest development design before committing your client to a purchase. Biodiversity Units UK can use a provisional brief to explore supply, provided any uncertainty is clearly identified.
When should I start sourcing off-site units for my client?
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What is the Ecologists for BNG Directory?
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The Ecologists for BNG Directory is a free regional resource created to help developers find vetted ecologists with practical BNG experience and local knowledge. If your practice works on BNG and would like to be considered for inclusion, contact Biodiversity Units UK.
Can I use the BNG Price Calculator to give my client an early budget?
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Yes. Upload the project’s statutory biodiversity metric to the free BNG Price Calculator to get a low, medium and high market estimate in seconds. It can help you give a client an early cost range without waiting for formal supplier quotes. Treat the result as a budget indication and update it when the final metric, design or unit requirement changes.
What information should I provide when requesting a unit quote?
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Provide the completed statutory metric, development location, required habitat types and unit quantities, and planning timetable. Identify outstanding design changes and clarify whether the enquiry is for an indicative price, reservation or purchase. Biodiversity Units UK uses this brief to source options, giving you a named contact for procurement queries.
How do I establish which units my client needs?
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Review the metric’s results and trading rules, rather than relying only on the overall percentage gain. Identify outstanding requirements separately for area habitats, hedgerows and watercourses, then test the proposed off-site solution in the development calculation. Metric guidance.
Can any biodiversity unit compensate for any habitat loss?
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No. Units must satisfy the statutory metric’s trading rules. These specify acceptable compensation according to habitat type and distinctiveness. A package can achieve the headline percentage while still failing the trading rules, so both must be checked.
Can area habitat, hedgerow and watercourse units be exchanged?
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No. These are separate unit types with separate requirements. An excess of area habitat units cannot resolve a hedgerow or watercourse shortfall. Specify each category clearly when requesting quotes. Statutory metric tools and user guide.
How does the spatial risk multiplier affect the purchase requirement?
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The location of the gain site relative to the development affects how much its units contribute. Apply the correct spatial risk multiplier in the metric before confirming the purchase quantity. Location rules differ between habitat categories. Off-site location guidance.
What should I check in the supplier’s metric and supporting information?
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Check habitat classifications, baseline evidence, proposed interventions, target conditions, strategic significance and relevant risk factors. Reconcile the units offered with the supplier’s calculation and the development’s requirements. Clarify assumptions or discrepancies before recommending the purchase. Metric assessment guidance.
Can my client buy units from more than one gain site?
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Yes. A solution can combine multiple gain sites and suppliers. Enter each contribution correctly in the development metric, check the combined results and trading rules, and ensure every allocation is recorded against the correct development. Biodiversity Units UK can bring options from different suppliers into one sourcing exercise, while you retain oversight of the technical assessment. Off-site purchasing guidance.
Can units be purchased before habitat creation is complete?
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Yes. Off-site gains can be allocated before habitat works start. Check the delivery timetable, target conditions and how time to delivery is reflected in the metric. Legal arrangements should clearly secure delivery and long-term management. Off-site delivery guidance.
What evidence should I obtain before finalising the Biodiversity Gain Plan?
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Obtain the gain site registration number, allocation details and supporting metric information. Check that the habitat types and quantities match your final calculation and that the recorded allocation relates to your client’s development. Under BNG Certainty, Biodiversity Units UK can help coordinate supplier information and Biodiversity Gain Plan preparation with your project team. Allocation guidance.
Is a reservation letter enough to demonstrate that units are secured?
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A reservation letter can support the proposed approach during planning, but it does not replace registration and recorded allocation. Off-site gains must be registered and allocated before the council can approve a Biodiversity Gain Plan relying on them. Off-site approval requirements.
Can I arrange registration or allocation on my client’s behalf?
14
An authorised agent can submit an allocation application, subject to the required permissions and evidence. Agree who will submit it, who will pay the fee and who will provide the confirmation. Purchasing units and recording their allocation are separate steps. Allocation application guidance.
What if my client’s design changes after units have been reserved?
15
Recalculate the shortfall and check whether the reserved package still meets the quantity and trading requirements. Reservation terms should address changes, substitutions, additional purchases and cancellation. Avoid assuming that a supplier will automatically adjust the agreement.
Who is responsible for managing purchased off-site habitats?
16
The gain site landowner is responsible under the legal arrangements securing the gains. Check the habitat management and monitoring plan, reporting arrangements and provisions for corrective action. Your consultancy’s responsibilities should be clearly defined in its appointment. Legal agreement guidance.
Does registration guarantee that a unit package is suitable for my client?
17
No. Registration establishes the gain site’s place on the national register; suitability still depends on the development’s metric requirements. Check habitat location, quantities and allocation, alongside the evidence required for planning approval. Metric guidance.
Can off-site units compensate for the loss of irreplaceable habitats?
18
Irreplaceable habitats require a separate approach. Standard unit purchases cannot substitute for the bespoke compensation arrangements required for their loss or deterioration. Address these requirements separately with the planning authority. Statutory metric guidance.
Can Biodiversity Units UK source units while I remain the client’s ecological adviser?
19
Yes. Biodiversity Units UK can coordinate the supplier search and commercial options while you retain your agreed ecological role. Under BNG Certainty, additional documentation and planning support can be coordinated with you. Define responsibilities for metric changes, technical sign-off and submission at the outset.
Can I involve my client directly in the unit sourcing process?
20
Yes. You can provide the technical brief and introduce the client to a named contact at Biodiversity Units UK. Agree who receives quotations and who can authorise reservations or purchases. This keeps technical advice and commercial decisions coordinated without assuming the consultant can commit the client.
FAQs for Planning Consultants
Start once the project ecologist identifies a likely shortfall. Early enquiries help establish availability and indicative costs, allowing you to incorporate procurement into the planning strategy and client programme. Confirm the final requirement before committing to a purchase. Biodiversity Units UK can help explore supplier availability while you coordinate the planning approach with the project ecologist.
When should I start exploring off-site biodiversity units for my client?
1
What is the Planners for BNG Directory?
2
Biodiversity Units UK maintains a regional directory of planning consultancies that we regularly recommend for projects and that have specialist BNG training. You can browse the Planners for BNG Directory by region. If you think your practice should be listed, contact info@biodiversityunits.com.
Where can I get a quick BNG cost indication for a client?
3
Use the free BNG Price Calculator for an early budget. Upload the project’s statutory biodiversity metric and it gives a low, medium and high market estimate in seconds. It is useful for feasibility and client conversations, but it is not a live supplier quote and should be refreshed when the metric or design changes.
How should I explain the off-site unit transaction timetable to a client?
4
The commercial purchase can be completed in a few days when the metric is clear, suitable units are available and the parties are ready to move. But purchase is only one part of the programme. Formal allocation needs the relevant planning decision, Natural England allows up to six weeks to determine an allocation application, and the LPA normally has eight weeks to determine the Biodiversity Gain Plan. Allow more time for rare habitats, legal issues, design changes or an unregistered gain site. Natural England allocation guidance. Biodiversity Gain Plan guidance.
Confirm whether mandatory BNG applies, the applicable gain target and the proposed delivery approach. Ask the ecologist to verify the habitat types and quantities required, and identify any unresolved design decisions that could change the purchase requirement.
What should I establish before recommending that my client buys units?
5
What should I discuss with the council at pre-application stage?
6
Discuss the proposed BNG strategy, on-site opportunities, likely off-site requirements and supporting evidence. Clarify local policy expectations and any anticipated legal arrangements. Early discussion can identify issues that could otherwise delay determination or approval of the Biodiversity Gain Plan. Planning guidance.
Does my client need to purchase units before submitting the planning application?
7
No. Units can be purchased before or after applying for permission. However, the application should demonstrate a credible delivery approach. Any off-site gains relied upon must be registered and allocated before the Biodiversity Gain Plan can be approved.
Can a supplier’s letter of support help with the planning application?
8
It can provide evidence of a potential off-site solution, particularly where it identifies suitable habitats and availability. It does not replace the statutory application information, the ecologist’s assessment or the registration and allocation needed for gain plan approval. Where available, Biodiversity Units UK can coordinate supplier support information. Confirm what it demonstrates and avoid treating it as evidence of completed allocation. Planning guidance and off-site guidance.
What information should I provide when requesting unit quotations?
9
Provide the latest completed metric, development location, planning reference if available, and anticipated programme. Explain whether the design is settled and whether your client needs an indicative quote, reservation or purchase.
How should I compare quotations from different suppliers?
10
Ask the ecologist to confirm that each offer meets the same technical requirement. Compare total costs, included services, availability, allocation timescales and contractual terms. Check whether quoted quantities account for relevant spatial multipliers and whether additional fees apply. Biodiversity Units UK can present supply options for comparison, while the project ecologist confirms technical suitability.
Can my client reserve units while the application is being determined?
11
Some suppliers offer reservations or option agreements. Check the deposit, reservation period, extension arrangements and refund terms. The agreement should address refusal of permission, programme delays and changes to the client’s unit requirements. These terms vary between suppliers. Biodiversity Units UK service information.
Does buying units mean my client needs a new section 106 agreement?
12
Not necessarily. If the supplier’s off-site gains are already secured by a suitable legal agreement, the developer does not need to enter a further agreement solely to secure those same gains. Separate obligations may still be required for other aspects of the development. Legal agreement guidance.
Can we use units outside the local planning authority’s area?
13
Yes. Off-site gains can be delivered elsewhere in England. Their location affects the metric contribution, so the ecologist should calculate any spatial risk multiplier before the client agrees a purchase quantity. Off-site location guidance.
The project ecologist should check habitat matching, trading rules, quantities and location factors. The planning consultant can coordinate that assessment with the planning strategy, supplier documents and council requirements. Statutory metric guidance.
Who should confirm that the proposed units are technically suitable?
14
What evidence do I need for the Biodiversity Gain Plan?
15
For purchased off-site gains, obtain the gain site registration number, recorded allocation details and supporting metric information. Ensure these match the final development calculation and planning permission. A purchase agreement or reservation letter alone does not establish recorded allocation. Allocation guidance.
Who is responsible for recording the allocation to my client’s development?
16
The landowner or an appropriately authorised applicant or agent can arrange allocation. Agree responsibilities with the supplier at the outset, including who submits the application, supplies supporting documents and pays the fee. Confirm that allocation has been recorded before relying on it. If using Biodiversity Units UK’s BNG Certainty service, agree how allocation coordination fits within the instructed scope. Allocation application guidance.
How should unit procurement fit into the discharge programme?
17
Allow time for the final metric, purchase arrangements, registration and allocation before gain plan approval. The normal determination period for the Biodiversity Gain Plan is eight weeks unless another period is agreed. Approval is required before commencement. Planning guidance.
What happens if the scheme changes after units have been reserved?
18
Ask the ecologist to reassess the shortfall against the revised drawings. Check whether the reserved package remains suitable and whether the contract permits changes, substitutions or cancellation. Resolve discrepancies before completing the purchase.
What should I check when dealing with a section 73 application?
19
Review the original permission, applicable transitional rules and whether the changes affect the approved BNG arrangements. A variation does not automatically require a fresh unit purchase. Coordinate any necessary updates to calculations, gain plans and allocation evidence. Section 73 guidance.
Does purchasing off-site units transfer all BNG responsibilities to the supplier?
20
No. The gain site landowner is responsible for delivering and managing the purchased habitats under the securing agreement. Your client remains responsible for meeting the development’s applicable planning requirements, including obtaining gain plan approval and delivering any on-site commitments. Legal responsibilities.
How can I help my client avoid procurement delays?
21
Keep the supplier, ecologist and design team working from the same metric and drawing revisions. Set deadlines for confirming quantities, completing the purchase and recording allocation. Flag scarce habitat requirements early and track outstanding documents alongside other pre-commencement matters.
Can Biodiversity Units UK help with the Biodiversity Gain Plan and condition discharge?
22
Yes, through the optional paid BNG Certainty service. Support can include Biodiversity Gain Plan preparation, documentation coordination and liaison with the project team and council. Agree who prepares, reviews and submits each document. Council approval remains a separate decision and cannot be guaranteed.
How should I divide responsibilities between my practice and Biodiversity Units UK?
23
Agree a clear scope with the client. Your practice can lead planning strategy and submission coordination, the ecologist can lead technical assessment, and Biodiversity Units UK can source units. BNG Certainty can add transaction and compliance support where instructed. Identify document owners and approval steps to avoid gaps or duplicate work.
FAQs for Architects
When should architects consider BNG in a project?
1
Consider BNG during site appraisal and concept design, before the layout is fixed. Understanding the site’s habitats early helps you coordinate buildings, access, drainage and landscaping while identifying any likely need for off-site units. Planning guidance.
What counts as on-site BNG when I am designing the scheme?
2
On-site BNG is biodiversity retained, enhanced or created within the development’s red line boundary and recognised by the statutory biodiversity metric. Depending on the scheme, that can include retained habitats, new or improved grassland, hedgerows, trees, ponds, green roofs and other qualifying habitats. Land outside the red line is off-site, even if the client owns it. Government on-site BNG guidance.
How does the biodiversity gain hierarchy affect design decisions?
3
For major development, the hierarchy means avoiding and reducing impacts to more distinctive habitats comes before relying on compensation. In practice, this can influence building positions, access, drainage, landscape areas and how much off-site BNG the client eventually needs to buy. Test options with the ecologist before the layout is fixed. Qualifying minor developments have more flexibility to consider on-site and off-site delivery together. Government BNG guidance.
Existing habitats can influence building positions, access routes and landscape areas. Work with the project ecologist to compare layouts and identify opportunities to retain valuable features, reduce habitat losses and provide achievable gains.
4
How can BNG influence the site layout?
Can green roofs, landscaping and drainage features reduce the need to buy units?
5
Yes, where they deliver habitats recognised by the statutory metric. Their contribution depends on the design, extent and achievable condition. Coordinate proposals with the ecologist and landscape designer before assuming they will resolve the shortfall. On-site guidance.
What is the architect’s role in securing biodiversity units?
6
Architects can coordinate the design information, flag likely requirements and help align procurement with the planning programme. The ecologist should confirm the technical unit requirement, while the client and their advisers agree the commercial and legal arrangements. Biodiversity Units UK can support the supplier search without requiring the architect to manage separate enquiries to each habitat bank.
What information should I obtain from the ecologist before approaching a unit supplier?
7
Request the latest completed metric, the required unit quantities and habitat types, and any relevant location constraints. Confirm which drawing revision the assessment uses and whether outstanding design decisions could change the requirement.
Can I request unit prices before the design is finalised?
8
Yes. Indicative quotes can help with feasibility and budgeting. Make clear that the requirement is provisional, and ask the ecologist to confirm the final package before your client commits to a purchase. Biodiversity Units UK’s BNG Price Calculator can provide an initial budgeting indication; supplier quotations and the ecologist’s assessment should inform the purchase.
What information will a biodiversity unit supplier need?
9
Typically, the supplier will need the development location, completed metric, required units and anticipated planning timetable. Identify whether your client needs an indicative quote, a reservation or a completed purchase. Biodiversity Units UK service information.
Can my client meet all their BNG requirements off-site?
10
Potentially, subject to the applicable biodiversity gain hierarchy and metric rules. Most developments must prioritise avoidance and on-site options. Since Aug 6, 2026, non-exempt minor developments can consider on-site and off-site delivery together. Delivery options.
Can land elsewhere in my client’s ownership count as on-site BNG?
11
Only land within the planning application’s red line boundary counts as on-site. Other land your client owns counts as off-site and must meet the relevant legal, registration and allocation requirements. Off-site guidance.
Do biodiversity units need to be purchased before submitting the planning application?
12
No. Units can be purchased before or after applying for permission. However, the application should demonstrate a credible BNG approach, and any off-site gains relied upon must be registered and allocated before the Biodiversity Gain Plan is approved. Planning and purchase guidance.
Can my client reserve units while awaiting planning permission?
13
Some suppliers offer reservations or option agreements. Check the deposit, reservation period, refund terms and what happens if permission is refused or the design changes. These arrangements vary between suppliers. Biodiversity Units UK service information.
How can I help my client compare unit quotations?
14
Ask the ecologist to confirm that each package meets the same technical requirement. Then compare the total price, included services, availability, allocation timetable and contractual terms. A lower price per unit does not necessarily mean a lower overall cost. Biodiversity Units UK presents supplier options in a consistent format to help the client and project team compare them.
Changes to buildings, access, drainage or landscaping may alter habitat losses and gains. Send revised drawings to the ecologist for review and check whether the unit package remains suitable before completing the purchase. Metric guidance.
What happens if the design changes after units have been quoted or reserved?
15
What documents should the project team obtain after purchasing units?
16
Obtain the purchase agreement, gain site registration number, evidence of allocation to the development and supporting metric information. Agree who will assemble these documents for the Biodiversity Gain Plan and check that they match the final scheme. Allocation guidance.
Does buying units mean the client can start construction?
17
No. For a development subject to the biodiversity gain condition, the council must approve the Biodiversity Gain Plan before development starts. Buying units is one step towards that approval. Approval requirements.
How should BNG be included in the project programme?
18
Allow time for ecological assessment, design coordination, sourcing units, commercial agreements, registration and allocation. Include Biodiversity Gain Plan approval before commencement; its normal determination period is eight weeks unless another period is agreed. Planning guidance.
What long-term management issues should influence the design?
19
Significant on-site enhancements must be maintained for at least 30 years. Consider maintenance access, realistic management budgets and who will control the habitat areas after completion. Coordinate these requirements with the landscape and estate management proposals. On-site management guidance.
Does purchasing off-site units remove other ecological design requirements?
20
No. Off-site units address the agreed BNG shortfall. The scheme must still meet applicable requirements concerning protected species, designated sites, retained habitats and other planning conditions. Planning guidance.
How can Biodiversity Units UK support early design budgeting?
21
The BNG Price Calculator can help indicate potential off-site unit costs once likely requirements are known. Biodiversity Units UK can then seek supplier options from the project brief. Treat early figures as provisional and update them when the ecologist confirms the metric and the design is settled.
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