BIODIVERSITY NET GAIN · LEGAL SECURING
Conservation Covenant vs Section 106 for Biodiversity Net Gain
Understand the two legal agreements used to secure BNG habitats and the separate on-site condition option.
For off-site biodiversity gains, landowners must secure the relevant habitat commitments through an appropriate legal agreement. A Section 106 planning obligation involves the relevant local planning authority. A conservation covenant involves a designated responsible body.
For significant on-site gains on development requiring planning permission, developers can also use a planning condition where appropriate. ACP can review ecological and planning evidence, while appropriately qualified lawyers advise on drafting and enforceability.
Conservation Covenant vs Section 106: the quick answer
Both mechanisms provide a legal agreement for Biodiversity Net Gain. However, they have different counterparties and legal frameworks.
The important BNG distinction
The question is not always “S106 or conservation covenant?”.
For off-site BNG, landowners must secure the habitat through a legal agreement before it can support the statutory off-site gain route.
For significant on-site gains on developments that need planning permission, current government guidance allows developers to secure the habitat through a legal agreement or a planning condition.
Therefore, the correct starting point is to identify what land and habitat commitment needs securing.
Key point:
There is no universal “better” mechanism. The suitable route depends on the project, land interests, planning position and the LPA or responsible body involved.
When does Biodiversity Net Gain need a legal agreement?
The securing requirements depend on where the biodiversity gain is being delivered.
Off-site biodiversity gains
To buy or sell off-site BNG gains, the habitat commitments need a legal agreement.
The agreement must secure the habitat creation or enhancement and long-term management. For statutory off-site BNG, the legal agreement must last for at least 30 years from completion of the relevant habitat enhancement works.
If the off-site gain is already legally secured by the landowner, a developer buying units from that gain site does not normally need to secure the same land again.
If your project is considering off-site delivery, our off-site biodiversity units page explains the wider sourcing and planning route.
Significant on-site gains
For developments that need planning permission, developers must secure significant on-site gains for long-term delivery.
Current GOV.UK guidance says developers must use either:
- a legal agreement; or
- a planning condition.
If the project team chooses a legal agreement, the available BNG types are a Section 106 planning obligation or a conservation covenant.
The maintenance period for an on-site BNG legal agreement must last for at least 30 years from completion of the development.
Other on-site ecological commitments
Government guidance also says some other on-site gains may need a legal agreement. This applies where gains contribute to locally important species or ecological networks, even if they are not significant.
The local planning authority should confirm the securing route for the specific project.
Important:
A planning condition can be relevant to significant on-site BNG, but it does not replace the legal agreement required for off-site gain sites.
Section 106 planning obligations for Biodiversity Net Gain
A Section 106 planning obligation is a legally binding planning obligation made under section 106 of the Town and Country Planning Act 1990.
For a BNG agreement, the relevant landowner interests enter the obligation with the local planning authority. The authority is responsible for monitoring and enforcing the BNG obligations secured through it.
In addition, planning obligations run with the land. Therefore, obligations can continue to affect successors in title, subject to the wording of the agreement and the statutory framework.
How S106 connects with the planning permission
Section 106 is part of the planning system. Authorities use it to secure obligations that a development needs.
The statutory tests in regulation 122 of the Community Infrastructure Levy Regulations 2010 require a planning obligation used as a reason for granting planning permission to be:
- necessary to make the development acceptable in planning terms;
- directly related to the development; and
- fairly and reasonably related in scale and kind to the development.
For BNG, an S106 can secure habitat delivery, management, monitoring, access, funding arrangements and other agreed responsibilities where the agreement appropriately includes those matters.
Who enforces an S106 BNG obligation?
The local planning authority is the enforcing body for a Section 106 planning obligation.
Therefore, the agreement should make the obligations, triggers and responsibilities sufficiently clear for long-term monitoring and enforcement.
What does an S106 cost?
There is no single national S106 legal or monitoring fee for BNG.
Legal drafting, monitoring and other charges vary between authorities and projects. Do not assume that a fee used by one LPA will apply to another.
For the wider categories that can affect a BNG budget, see our BNG costs and pricing guide.
Key point:
Section 106 is an established planning-obligation route. It is not automatically required for every on-site BNG commitment, and its cost or timescale cannot be generalised nationally.
Conservation covenants for Biodiversity Net Gain
A conservation covenant is a private, voluntary agreement created under Part 7 of the Environment Act 2021.
A landowner and responsible body enter the agreement. They must intend it for the public good, give it a conservation purpose and execute it as a deed.
For BNG, a conservation covenant can provide the legal framework for long-term habitat creation, enhancement, management and monitoring.
What is a responsible body?
A responsible body is an organisation able to enter conservation covenants under the Environment Act 2021.
Defra maintains the current list of designated responsible bodies in England. It includes different types of organisations, including public bodies, local authorities, charities and private-sector organisations that meet the designation requirements.
A landowner should not assume that every responsible body will accept every proposed covenant. Therefore, confirm scope, fees, monitoring arrangements and acceptance criteria with the chosen body.
Does a conservation covenant bind future owners?
Conservation covenants are designed to support long-term obligations connected with land.
Government guidance explains that they can pass conservation commitments to future landowners. Therefore, ask the project’s legal adviser to check the exact effect, duration and land interests.
Is every conservation covenant a 30-year agreement?
No.
The Environment Act allows conservation-covenant obligations to have different durations. However, a conservation covenant securing statutory BNG must meet the minimum 30-year requirement for the relevant habitat commitment.
Key point:
The 30-year rule comes from the BNG securing requirement. It should not be presented as the universal duration of every conservation covenant.
Section 106 vs conservation covenant for BNG
The table below compares the practical features of the two legal-agreement routes.
| Feature | Section 106 planning obligation | Conservation covenant |
|---|---|---|
| Main legal framework | Section 106 of the Town and Country Planning Act 1990 | Part 7 of the Environment Act 2021 |
| BNG counterparty | Relevant landowner interests and the local planning authority | Landowner and a designated responsible body |
| Main enforcing body | Local planning authority | Responsible body |
| Connection with planning | A planning obligation used within the planning system | A conservation agreement that does not depend on the LPA being the counterparty |
| Off-site BNG | Can secure an off-site gain site | Can secure an off-site gain site |
| Significant on-site BNG | Can be used where a legal agreement is the chosen securing route | Can be used where a legal agreement is the chosen securing route |
| Planning-condition alternative | Significant on-site gains may instead be secured by a planning condition where appropriate | The same planning-condition alternative may mean no separate BNG legal agreement is needed for that on-site commitment |
| Duration when used for statutory BNG | Must meet the relevant BNG minimum securing period | Must meet the relevant BNG minimum securing period |
| Long-term monitoring | Agreed with the LPA | Agreed with the responsible body |
| Land and successor implications | Planning obligations run with the land and can bind successors in title | Conservation commitments can bind future landowners under the statutory covenant framework |
| Gain-site registration | A qualifying legal agreement can support registration of an off-site biodiversity gain site | A qualifying legal agreement can support registration of an off-site biodiversity gain site |
| Cost and timing | Authority- and project-specific | Responsible-body- and project-specific |
| Legal advice | Obtain project-specific legal advice | Obtain project-specific legal advice |
What the table does not tell you
The table does not identify a universally cheaper, quicker or more enforceable route.
In practice, the decision also depends on:
- who owns or leases the land;
- whether mortgages or other land interests need to be addressed;
- whether the LPA is prepared to use an S106 for the proposal;
- whether a designated responsible body will accept the covenant;
- the monitoring and funding model;
- whether the land will be registered as a biodiversity gain site;
- the timing of habitat enhancement works; and
- the legal and ecological documents already prepared.
Which BNG securing route should you investigate?
Start with the habitat commitment, not with a preferred legal document.
1. Are you securing off-site biodiversity gains?
Yes.
A legal agreement is required.
The landowner will need a BNG legal agreement that secures the habitat for the required long-term period. The two legal-agreement types are:
- a Section 106 planning obligation with an LPA; or
- a conservation covenant with a designated responsible body.
The project team should then confirm which route is available and appropriate for that land.
No.
Go to the on-site question.
2. Are you securing significant on-site gains for a development that needs planning permission?
Yes.
Current government guidance allows:
- a legal agreement; or
- a planning condition.
If the project team chooses a legal agreement, it can then consider the S106 or conservation-covenant routes.
No or not sure.
Confirm with the LPA whether any on-site habitat commitment still needs legal securing.
3. Are you buying units from a gain site that is already legally secured and registered?
If the landowner has already secured the gain site, the developer does not normally need another legal agreement for that same off-site land.
However, the project still needs the correct allocation evidence and Biodiversity Gain Plan information.
4. Before deciding the route
Confirm:
- the landowner and leasehold position;
- the habitat areas and BNG units being secured;
- the responsible party for creation, management and monitoring;
- the habitat-enhancement completion point;
- the monitoring and access arrangements;
- the funding arrangements;
- the gain-site registration strategy, where relevant; and
- the legal adviser responsible for drafting or reviewing the agreement.
Decision note:
ACP can help organise and check the ecological information behind these decisions. Your solicitor, LPA or responsible body must confirm the legal route and final deed wording.
BNG securing-route decision checkpoints
Use these checkpoints to structure a review. They are not a legal eligibility ruling, a metric calculation or an enquiry submission.
- Identify the gainOff-site, significant on-site, or another on-site commitment?
- Check whether agreement is neededOff-site requires S106 or covenant. For significant on-site gains a condition may be an option.
- Identify the counterpartyS106: relevant LPA. Covenant: designated responsible body.
- Agree the evidenceMatch the legal description, metric, habitats, boundaries and HMMP.
- Check duration and enforcementConfirm 30-year BNG requirement and correct start point.
- Obtain legal adviceQualified advisers draft and advise on enforceability and property rights.
Next step: collect the project evidence and discuss unresolved gates with the appropriate ecologist, land agent or legal adviser.
What information should the BNG legal agreement align with?
In practice, a legal agreement should not sit separately from the ecological evidence.
The habitat commitments, management requirements and monitoring arrangements should align across the BNG documents used for the project.
For example, common information includes:
- the land and habitat areas covered by the agreement;
- the habitat creation or enhancement being committed to;
- the intended habitat condition and biodiversity value;
- the date or trigger for completing habitat enhancement works;
- who is responsible for creating or enhancing the habitats;
- who is responsible for long-term management;
- who is responsible for monitoring;
- the monitoring schedule and site-access arrangements;
- the actions required if habitat delivery does not progress as planned;
- permitted changes and dispute arrangements;
- funding and payment arrangements where applicable;
- the pre-enhancement biodiversity value from the statutory biodiversity metric; and
- the way off-site enhancements will be allocated to developments where relevant.
In addition, a Habitat Management and Monitoring Plan can provide the detailed management and monitoring schedule that supports these commitments.
Why consistency matters
Therefore, the legal agreement, Biodiversity Gain Plan, statutory biodiversity metric and habitat-management information should describe the same delivery strategy.
For example, habitat types, areas, target conditions and management responsibilities should not conflict between documents.
Therefore, finding inconsistencies before the legal team completes drafting can reduce avoidable clarification later.
How the legal agreement fits biodiversity gain-site registration
Landowners must legally secure off-site land before it can support the statutory gain-site route.
Current GOV.UK registration guidance requires evidence that includes:
- proof of ownership or qualifying leasehold interest;
- the gain-site boundary;
- a legal agreement securing the land for at least 30 years;
- the completed statutory biodiversity metric calculation;
- a Habitat Management and Monitoring Plan; and
- the required local land-charge information.
The legal agreement must be a Section 106 planning obligation or a conservation covenant.
However, registration is a separate process from choosing and drafting the legal agreement. The applicant must also register the site and correctly allocate the relevant enhancement where a development uses the units.
For the registration sequence and evidence requirements, see our guide to registering a biodiversity gain site.
Already buying registered off-site units?
Similarly, if a landowner has already secured and registered the gain site, the developer should check the registration and allocation evidence rather than assume a new legal agreement is needed for the same land.
For terminology around biodiversity units and statutory credits, see BNG units and credits explained.
What ACP can support — and what needs a lawyer
ACP supports the ecological and BNG information that sits behind the legal agreement.
We do not provide legal advice or draft legal deeds.
| ACP can support | Your legal adviser / agreement counterparty should handle |
|---|---|
| Review the BNG strategy and on-site/off-site delivery position | Legal advice on the appropriate deed or planning obligation |
| Prepare or review ecological baseline information | Drafting and negotiating the legal agreement |
| Prepare or review the statutory biodiversity metric | Land-title, mortgagee and leasehold legal issues |
| Prepare habitat-management and monitoring information within the agreed consultancy scope | Legal interpretation of obligations and liabilities |
| Map habitat areas and ecological commitments | Execution formalities and deed wording |
| Check ecological consistency between the metric, plans, BGP and HMMP | Advice on tax, property rights or contractual risk |
| Provide ecological information requested by an LPA or responsible body | Formal advice on enforceability, variation or discharge |
Working alongside the project team
A practical BNG legal agreement may involve the landowner, developer, ecological consultant, planning consultant, solicitor, LPA and, for a conservation covenant, the responsible body.
As a result, ACP can help keep the ecological information consistent while those parties agree the legal terms.
What to send us for an initial BNG legal-securing review
You do not need a completed legal agreement before asking ACP to review the ecological position.
For an initial review, send the following where available:
Site location and red-line boundary
This helps establish the development and gain-site context.
Current planning status
Include the planning reference, decision status or relevant LPA correspondence if available.
BNG assessment or statutory biodiversity metric
This identifies the units and habitat commitments being relied upon.
On-site and off-site delivery strategy
Tell us which gains are proposed on the development site and which are proposed elsewhere.
Habitat plans or landscape plans
These help confirm the land and habitat areas that need to align with the securing mechanism.
Biodiversity Gain Plan or draft BGP
If one exists, we can check the ecological commitments against the proposed legal route.
Habitat Management and Monitoring Plan or draft management information
In turn, this helps identify management, monitoring and responsibility requirements.
Gain-site information
If off-site land is involved, include any registration reference, landowner information or current responsible-body/LPA correspondence that you are authorised to share.
Legal-adviser contact or heads of terms, where appropriate
If legal drafting has started, ACP can focus on the ecological schedules and consistency questions rather than legal wording.
Do not have every document yet?
Send the information already available. We can identify the ecological gaps before further BNG work is scoped.
Need the BNG evidence aligned before the legal agreement is finalised?
ACP can review the metric, habitat commitments, management information and gain-site context to identify what ecological evidence should be consistent across the project documents.
We can then work alongside your planning and legal team while the appropriate parties confirm the Section 106, conservation covenant or planning-condition route.
For legal drafting, interpretation or advice on land interests, use an appropriately qualified legal professional.
Frequently asked questions about conservation covenants and Section 106 for BNG
What is the main difference between a conservation covenant and a Section 106 agreement?
A Section 106 planning obligation sits within the planning framework. The local planning authority enforces it.
A conservation covenant is an agreement between a landowner and a designated responsible body under Part 7 of the Environment Act 2021.
Both provide BNG legal agreements. However, they have different counterparties and statutory frameworks.
Which is better for Biodiversity Net Gain: S106 or a conservation covenant?
There is no universal better route.
The practical choice depends on the habitat commitment, the land interests, the planning context, the LPA’s approach and whether a suitable responsible body will enter a conservation covenant.
Therefore, confirm the cost and timescale for the specific project.
Does off-site BNG always need a legal agreement?
Yes. Landowners must legally secure off-site BNG gains that enter the statutory system.
The legal agreement can be a Section 106 planning obligation or a conservation covenant and must meet the relevant long-term BNG requirements.
Where a developer buys units from an already secured gain site, the developer does not normally need to secure that same land again.
Can significant on-site BNG be secured by a planning condition?
Yes.
For developments that need planning permission, current government guidance allows developers to secure significant on-site gains through a legal agreement or a planning condition.
The LPA should confirm the appropriate route for the specific development.
How long must a BNG legal agreement last?
For relevant statutory BNG commitments, the responsible parties must secure and manage the habitat for at least 30 years.
The start point differs.
For on-site BNG under an ordinary planning permission, the maintenance period starts on completion of the development. For off-site BNG, it starts on completion of the relevant habitat enhancement works.
Who can be a responsible body for a conservation covenant?
A conservation covenant must be with a responsible body under the Environment Act 2021.
Defra publishes and updates the list of designated responsible bodies in England. Landowners can approach an appropriate designated body, but acceptance, scope and charges are organisation-specific.
Can a project use both an S106 and a conservation covenant?
Potentially, yes.
Different land or obligations within a wider project can have different securing arrangements. However, a project should not add both mechanisms to the same commitment without a clear reason.
The legal and planning team should confirm how the arrangements interact.
Does ACP draft Section 106 agreements or conservation covenants?
No.
ACP provides ecological and Biodiversity Net Gain consultancy. We can prepare or review the ecological evidence, metric, habitat information and management requirements that support the legal process.
The legal agreement itself should be drafted and reviewed by appropriately qualified legal professionals.
Do both mechanisms bind future landowners?
Both mechanisms can create obligations that continue with the land.
Section 106 planning obligations run with the land and can bind successors in title. Conservation covenants are specifically designed to support long-term conservation commitments that can continue after ownership changes.
Therefore, ask the project’s legal adviser to confirm the exact legal effect.
Is a conservation covenant always cheaper than a Section 106 agreement?
No universal answer applies.
Legal fees, monitoring costs, responsible-body charges, LPA charges, land complexity and negotiation requirements vary between projects.
Obtain current project-specific fee information before budgeting.
Discuss Your BNG Legal-Securing Evidence
Tell us what habitat gain needs securing, the planning stage and which metric, boundary or management documents are available.
You do not need every document before contacting us. Please summarise what you have; we can discuss how to share supporting information securely if a review is appropriate.
Your project, site location and contact details can be provided through the enquiry form.
Prefer to talk? 0330 236 7329 · hello@acp-consultants.com.
Sources and scope
The following official guidance was checked on 14 October 2026. Guidance, government fees, legal requirements and statutory-metric tools may change.
Enter a legal agreement for BNG · Conservation covenant agreements · Planning obligations · Register a biodiversity gain site.
Scope of this guide. This is a comparison of BNG securing routes, not legal advice or contract drafting. Whether a condition, Section 106 planning obligation or conservation covenant is suitable depends on the location and nature of the gains, land interests, planning permission and relevant authority or responsible body. A lawyer should advise on enforceability and drafting.
This information supports initial ecological and planning discussions in England. It does not determine a planning outcome or replace project-specific ecological, planning, legal or commercial advice.
Disclaimer date: October 2026.