A practical guide to Biodiversity Net Gain — what it means for your planning application, when you need off-site units, and how to make BNG compliance straightforward.
Biodiversity Net Gain (BNG) is a legal requirement under the Environment Act 2021 that most new developments in England must leave biodiversity in a measurably better state than before. In practice, this means demonstrating a minimum 10% increase in biodiversity value compared to the pre-development baseline of your site.
BNG became mandatory on 12 February 2024 for major developments (10 or more dwellings, or sites over 1 hectare) and on 2 April 2024 for minor and small sites. It applies to all qualifying planning permissions granted under the Town and Country Planning Act 1990.
Biodiversity value is measured using the statutory Biodiversity Metric (currently version 4.0), a spreadsheet-based calculator published by Natural England. The metric assigns numerical values to habitats based on their type, condition, area, and strategic significance. Your development must achieve a post-intervention score at least 10% higher than the pre-development baseline — across area-based units, hedgerow units, and watercourse units where relevant.
Crucially, BNG is a pre-commencement condition. You cannot lawfully begin work on site until you have submitted and had approved a Biodiversity Gain Plan that demonstrates how the 10% uplift will be achieved. The habitats created or enhanced must then be secured and managed for at least 30 years.
If you are submitting a planning application that results in the loss or disturbance of any habitat — including grassland, scrub, hedgerows, or even bare ground with ecological value — you almost certainly need to comply with BNG. Here is how it applies across different development types.
All residential developments that require planning permission must comply with BNG, from large housing estates to single-dwelling plots. The scale of the requirement depends on the pre-development baseline: a greenfield site with species-rich grassland will require significantly more biodiversity uplift than a brownfield conversion. Even small residential schemes of one or two houses can trigger substantial off-site unit requirements if the site has moderate or high-distinctiveness habitats.
Office developments, warehousing, retail parks, and industrial units all fall within scope. Commercial projects on previously developed land may have lower baseline scores, but the 10% uplift still applies. Large logistics and distribution centres — increasingly common across southern England — often require significant off-site BNG delivery due to their footprint and the difficulty of creating meaningful habitat on site.
Road schemes, energy infrastructure, and utility projects granted planning permission under the Town and Country Planning Act are already subject to BNG. From November 2026, BNG will also become mandatory for Nationally Significant Infrastructure Projects (NSIPs) consented under the Planning Act 2008 — including major road schemes, railway works, power stations, and large-scale solar farms. This expansion is expected to drive significant new demand for off-site BNG units.
A limited number of development types are exempt from BNG:
If you are unsure whether your project is exempt, check with your local planning authority or ecological consultant before assuming you are outside scope. Getting this wrong can cause serious delays.
Understanding the BNG process early — ideally at pre-application stage — saves time, money, and planning risk. Here is the typical sequence from start to sign-off.
An ecologist visits your site to map and assess every habitat present — grassland, hedgerows, trees, ponds, scrub, bare ground. This survey must be conducted before any site clearance or enabling works. Clearing habitat before survey is recorded as “habitat degradation” and the metric will use the pre-degradation condition, penalising you with additional units. The baseline survey data is entered into the statutory Biodiversity Metric.
Your ecologist inputs the baseline habitats and the proposed post-development habitats into the Biodiversity Metric 4.0 spreadsheet. The metric calculates the change in biodiversity value across three unit types: area-based habitat units, hedgerow units, and watercourse units. It identifies whether you achieve the 10% uplift on-site or whether you have a deficit that must be met off-site.
If the metric shows a deficit in any unit type, you need to source off-site units. The metric specifies the number and type of units required. Spatial risk multipliers may apply depending on the distance and ecological relationship between your development and the habitat bank — units from a bank in the same planning authority or LNRS area typically carry the lowest multiplier.
Contact a registered habitat bank to confirm availability, pricing, and spatial risk for your specific development. At The Ferals, we can review your metric and provide a quote within 48 hours. You will need to agree a purchase contract that specifies the unit types, quantities, and allocation details.
Your ecologist prepares a Biodiversity Gain Plan — the formal document submitted to the planning authority that sets out how you will achieve the 10% uplift. It covers on-site habitat creation and management, off-site unit allocations (with confirmation from the habitat bank), and the 30-year management and monitoring arrangements. This is a pre-commencement condition: it must be approved before you can lawfully start construction.
Submit the Biodiversity Gain Plan to the local planning authority for approval. The authority will check that the metric is correctly completed, the off-site units are from a registered biodiversity gain site, and the management plan covers the full 30-year period. Once approved, the BNG pre-commencement condition is discharged and construction can begin.
On-site habitats must be managed according to the approved Habitat Management and Monitoring Plan for at least 30 years. Off-site habitats are managed by the habitat bank under their own legal agreement — when you buy units from a registered bank like The Ferals, the 30-year management obligation sits with us, not with you. Monitoring reports are submitted to the planning authority at agreed intervals.
Developers have three options for delivering BNG: creating or enhancing habitats on the development site itself, purchasing off-site units from a registered habitat bank, or buying statutory credits from Natural England as a last resort. Most developments use a combination of on-site and off-site delivery.
Until recently, a mitigation hierarchy applied to all developments, requiring developers to maximise on-site delivery before looking off-site. In 2026, the government removed this hierarchy for minor and small developments, giving developers on smaller sites the freedom to choose the delivery route that works best for their project. For major developments, the hierarchy still formally applies, though in practice most planning authorities accept that constrained sites cannot deliver meaningful habitat on-site.
On-site BNG delivery makes sense when your development has space for genuine habitat creation — large greenfield sites, master-planned communities with public open space, or projects where landscape design can incorporate native planting, ponds, and meadow areas. The habitats created on-site must be ecologically meaningful and managed for 30 years. A token strip of wildflower turf along a boundary fence will not satisfy the metric or the planning authority.
Off-site delivery through a registered habitat bank is often the more practical, cost-effective, and ecologically beneficial route. This is particularly true for:
A dedicated habitat bank like The Ferals delivers higher-quality biodiversity outcomes than scattered patches of habitat across development sites. Our 250 acres in the Tarrant Valley, adjacent to the National Trust’s Kingston Lacy rewilding project, contribute to landscape-scale nature recovery in a way that isolated on-site habitats never can. If your development is in Dorset or a neighbouring county, see our dedicated page on off-site BNG units in Dorset.
BNG costs vary significantly depending on the size and location of your development, the pre-development baseline, the habitat types involved, and whether you deliver on-site, off-site, or through statutory credits.
As a general guide, off-site units from a registered habitat bank are significantly cheaper than statutory credits. The government has deliberately priced statutory credits at a premium (currently £42,000 per area unit for medium distinctiveness habitats) to incentivise developers to use the private market. Habitat bank prices are typically a fraction of the statutory credit price.
On-site delivery has its own costs — ecological design, landscape implementation, and crucially the 30-year management and monitoring obligation that must be funded and secured. For smaller developments, the overhead of on-site management often makes off-site units the more economical choice.
For a detailed breakdown of BNG unit pricing, including statutory credit rates and habitat bank pricing factors, see our guide to BNG unit costs.
The Ferals is a 250-acre registered habitat bank at Tarrant Keyneston in Dorset, listed on the Natural England biodiversity gain site register (reference BGS-180925001). We supply off-site BNG units to developments across England, with the lowest spatial risk for projects in Dorset, BCP, and neighbouring planning authorities.
Here is what makes buying from The Ferals straightforward:
For a step-by-step guide to the purchasing process, see How to Buy BNG Units. For available unit types and pricing, visit our BNG units for sale page. Or simply get in touch with your metric and we will take it from there.
BNG is still relatively new, and we regularly see developers and their consultants make avoidable errors that cost time and money. Here are the most common.
One of the most significant upcoming changes to BNG is the extension of the mandatory requirement to Nationally Significant Infrastructure Projects (NSIPs) from November 2026. NSIPs are major infrastructure schemes — power stations, wind farms, large solar installations, major road and rail projects, airports, ports, and large-scale water infrastructure — that are consented through a Development Consent Order (DCO) under the Planning Act 2008 rather than through the Town and Country Planning Act.
Until November 2026, NSIPs are not formally subject to mandatory BNG, though many promoters are already voluntarily incorporating biodiversity net gain into their Environmental Impact Assessments. Once the mandate takes effect, NSIPs will need to demonstrate the same 10% minimum biodiversity uplift as other developments.
The scale of NSIP developments means the demand for off-site BNG units is expected to increase substantially. A single major road scheme or solar farm can require hundreds of biodiversity units — far more than can realistically be delivered on-site. Habitat banks with available capacity, established habitats, and robust legal frameworks will be well-positioned to supply these projects.
For a detailed analysis of what the NSIP expansion means for developers and infrastructure promoters, read our article: BNG for NSIPs: What the November 2026 Mandate Means for Developers.
Biodiversity Net Gain is a legal requirement under the Environment Act 2021 that most planning applications in England must deliver at least a 10% increase in biodiversity value compared to the pre-development baseline. It has been mandatory since February 2024 for major developments and April 2024 for small sites.
Most planning applications that involve the loss or disturbance of any habitat require BNG. This includes residential developments of all sizes, commercial and industrial projects, and infrastructure schemes. Exemptions exist for householder applications, developments below the de minimis threshold (typically less than 25 square metres or 5 metres of linear habitat), certain self-build schemes, and some retrospective applications.
Yes. Developers can deliver BNG through a combination of on-site habitat creation, off-site units from a registered habitat bank, or statutory credits from Natural England. A 2026 rule change removed the previous mitigation hierarchy for minor and small developments, giving developers more flexibility to choose off-site delivery where it makes practical and ecological sense.
Off-site BNG unit prices vary depending on habitat type, distinctiveness level, and provider. As a general guide, off-site units from a registered habitat bank are significantly cheaper than statutory credits purchased from the government. For detailed pricing information, visit our BNG unit cost guide or contact us directly for a quote based on your metric.
BNG units are purchased from registered habitat banks — private landowners who have committed to creating and managing habitats for at least 30 years, secured through a legal agreement. Statutory credits are purchased from the government as a last resort and are deliberately priced far higher to incentivise the use of habitat banks. Credits should only be used when no suitable habitat bank units are available.
At The Ferals, we can typically confirm availability and provide a quote within 48 hours of receiving your Biodiversity Metric. From agreement to completion, the process usually takes two to four weeks, including legal review and allocation. We recommend engaging early — ideally at pre-application stage — to avoid delays to planning consent.
Yes. From November 2026, Biodiversity Net Gain becomes mandatory for Nationally Significant Infrastructure Projects. NSIPs will need to demonstrate a minimum 10% biodiversity net gain, and given the scale of these projects, the demand for off-site units is expected to increase significantly. Read our full analysis of BNG for NSIPs.
BNG is a pre-commencement planning condition. If you begin work on site before discharging the condition — by submitting an approved Biodiversity Gain Plan — you risk enforcement action, stop notices, or even prosecution. The planning authority can also refuse to discharge other conditions until BNG compliance is demonstrated.
Send us your Biodiversity Metric and we will confirm availability, pricing, and spatial risk within 48 hours.
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