Biodiversity Gain Plan: Content, Submission and Approval

Biodiversity gain plan: turning your BNG strategy into approval

A biodiversity gain plan explains how a development will achieve the statutory biodiversity gain objective in England. Sometimes called a BNG gain plan, it brings together the baseline, post-development habitat value, registered off-site gains and any statutory credits needed as a last resort. If you are looking for a biodiversity gain plan template, the important starting point is understanding the evidence behind each answer. A completed form cannot secure approval if the metric, habitat drawings and delivery arrangements do not support it.

Collington Winter Environmental helps applicants connect planning-stage BNG assessments with the detailed information needed before development starts. The plan should describe a deliverable outcome, not an ambition that depends on unresolved land ownership, unsuitable habitat proposals or an unverified off-site purchase. Preparing its supporting evidence early can make the transition from planning permission to implementation clearer for everyone involved.

When is a biodiversity gain plan required?

For development within the mandatory BNG regime, planning permission is subject to the statutory biodiversity gain condition under Schedule 7A of the Town and Country Planning Act 1990. This framework was introduced by the Environment Act 2021 and generally requires at least a 10% gain. It commenced for major development from 12 February 2024 and small sites from 2 April 2024, with exemptions and transitional arrangements affecting individual cases.

The gain plan is normally submitted after planning permission is granted. It must be approved by the relevant planning authority before development commences. That timing is important: the final statutory plan is not usually the same document as the BNG statement submitted with the application. Nevertheless, early application evidence should show a credible route to compliance, rather than leaving the entire delivery strategy for later.

Not every permission needs a gain plan. Householder applications, qualifying self-build and custom-build schemes and certain very limited habitat impacts may be exempt. Permitted development is outside this mandatory planning framework. Check applicability before commissioning a detailed submission, using our guides to whether BNG is mandatory and when BNG assessments are required.

What does a biodiversity gain plan contain?

Development details and the biodiversity gain hierarchy

The plan identifies the development and relevant planning permission, so the authority can connect the proposed gains to the correct scheme. It should explain the steps taken to minimise adverse habitat effects and how the biodiversity gain hierarchy has been applied. This means addressing avoidance, mitigation and habitat delivery in a reasoned sequence, rather than presenting off-site purchasing as the automatic first option.

The explanation should be specific to the development. If a layout has been altered to retain a hedgerow or reduce grassland loss, show how the drawings and metric reflect that change. Where opportunities for on-site delivery are constrained, explain the real constraints. Generic statements about site limitations are less useful than a clear account of access, drainage, existing habitats, operational needs and the available management area.

The pre-development biodiversity value

The baseline is the starting biodiversity value against which gain is measured. It needs to be supported by the appropriate habitat survey, mapped parcels and metric calculation. Habitat type, area or length, condition and strategic significance should be recorded consistently. The relevant baseline date must also be clear, including any justified earlier date or applicable habitat degradation provisions.

A gain plan should not silently replace the application baseline with a more convenient figure. If an error or change needs to be addressed, explain the reason and maintain an auditable record of the evidence. Earlier habitat clearance can have legal implications for the baseline, so applicants should disclose site management and clearance history rather than assuming that the latest survey always provides the correct starting point.

The post-development biodiversity value

The post-development calculation describes retained, enhanced and newly created habitats associated with the permitted development. It must match the actual scheme and supporting habitat plans. Proposed habitats need realistic target conditions, establishment periods and management prescriptions. A high-condition habitat should not be selected merely because it produces enough units to pass the calculation.

The metric takes account of the risks and delays associated with habitat creation and enhancement. These adjustments can mean that replacing the area of a lost habitat with the same area of a new habitat does not replace its biodiversity value. Our biodiversity metric calculations service helps applicants understand those effects and test suitable design responses before finalising the gain plan.

Registered off-site gains and statutory credits

Where off-site gains are used, the plan must identify the relevant registered allocation and show how it contributes to the development's biodiversity value. Natural England operates the biodiversity gain site register. An offer letter or an agreement in principle to buy units is not the same as a completed allocation of registered gains to the development.

The type and location of the units matter. Trading rules must be met and the spatial risk multiplier applied correctly. If statutory biodiversity credits are needed, their use must reflect their last-resort position in the delivery hierarchy and the necessary purchase evidence. Credits should not be confused with commercial off-site biodiversity units, which are delivered through habitat sites and registered allocations.

Using a biodiversity gain plan template properly

The government publishes a standard biodiversity gain plan template that provides a useful structure for the required information. Check that you are using the current version and any relevant submission instructions from the planning authority. The template prompts the applicant to identify the development, explain the hierarchy and present the biodiversity values and delivery route.

However, a template is a framework, not an ecological assessment. It does not establish that the baseline is correct, that habitat trading is acceptable or that land can be managed as proposed. Every statement should be supported by the metric, plans, legal arrangements or other relevant evidence. Repeating a percentage from an earlier report without checking the final design can leave a material gap in the submission.

Documents to coordinate before submission

A coherent package commonly includes the completed gain plan, final statutory metric or eligible Small Sites Metric, baseline and proposed habitat plans, and the supporting management information. Where relevant, it also includes evidence of registered off-site allocation, statutory credit purchase and legal security for long-term habitat delivery. The exact supporting material depends on the proposal and the authority's assessment requirements.

Use consistent habitat parcel references, plan revisions and area measurements across the package. Check that the landscape drawing does not show a different habitat mix from the metric and that engineering revisions have not removed land intended for gain. These checks are particularly important where several consultants have worked on the scheme or the design has changed since permission was granted.

How the HMMP supports the BNG gain plan

A habitat management and monitoring plan, often shortened to HMMP, explains how the promised habitat outcomes will be achieved and maintained. It is distinct from the biodiversity gain plan but closely linked to it. The gain plan establishes the biodiversity outcome being relied on; the HMMP sets out the management tasks, timing, responsibilities and monitoring needed to deliver that outcome.

For significant on-site habitat enhancements and registered off-site gains, the applicable arrangements must secure delivery and maintenance for at least 30 years. The management period and its starting point should be clear in the relevant documents and legal mechanism. Long-term obligations need to be understood by the party that will own or manage the land, not merely the team preparing the planning application.

A useful HMMP identifies target habitat conditions, establishment works, ongoing management, monitoring methods and reporting requirements. It should also address remedial action if habitats are not progressing as expected. Simply requiring an annual cut or occasional inspection may be insufficient where the metric assumes a demanding target condition. Management should reflect the ecology of the habitat and the site's practical constraints.

Approval, amendments and phased development

The planning authority assesses whether the gain plan meets the statutory requirements. The determination period is generally eight weeks from the day after receipt unless another period is agreed in writing. A well-coordinated submission helps the authority follow the evidence, but no consultant can guarantee approval. An unresolved shortfall, unsuitable trade or unregistered allocation can prevent a plan from being acceptable.

Do not assume the authority will correct a defective metric or reconcile contradictory drawings on the applicant's behalf. Resolve discrepancies before submission and respond clearly to any queries. If the development or its habitat delivery changes later, take advice on whether an updated gain plan, a planning amendment or changes to legal arrangements are required. An approval should remain aligned with what will actually be built and managed.

Phased developments have additional provisions for overall and phase-specific gain plans. An overall strategy must be capable of supporting the individual phases rather than deferring all habitat delivery to an uncertain final stage. Early coordination is particularly important where land transfers, infrastructure delivery or off-site allocations are shared across different phases or development partners.

Why choose Collington Winter

Collington Winter Environmental is based in Bolton and works throughout England. Our Managing Director, Olivia Collington, is a Chartered Environmentalist with the IES and has experience with the DEFRA Statutory Biodiversity Metric and habitat bank offsetting. We focus on making the relationship between habitat evidence, metric outputs and practical delivery understandable, so that a gain plan is supported by a coherent implementation strategy.

For wider background, read what biodiversity net gain is and how habitat banking can support appropriate off-site provision. If you need help preparing or reviewing a biodiversity gain plan, call 01204 939 608 or use our contact page.