Legal agreements to secure your biodiversity net gain

How land managers, developers, local planning authorities and responsible bodies can legally secure land or habitat enhancements for biodiversity net gain.

Applies to England

This draft guidance explains what will apply when BNG becomes mandatory. We will continue to update this guidance.

You must legally secure off-site gains or significant on-site gains for at least 30 years.  

You do not need to secure non-significant on-site enhancements unless they contribute to locally important species or ecological networks. Check with your local planning authority (LPA) if you’re not sure. 

Secure on-site gains 

To secure significant on-site habitat enhancements, you must have a legal agreement or planning condition

A planning condition is different to the biodiversity gain condition to achieve 10% net gain. 

You must secure on-site gains for at least 30 years from the date you complete the development. 

Secure off-site gains 

If you’re securing land to buy or sell off-site gains, you must have a legal agreement. 

You must secure off-site gains for at least 30 years from the date you finish the habitat enhancement. 

How to legally secure gains 

There are 2 types of legal agreement for BNG: BNG

As part of the legal agreement, you (or a third party you have sub-contracted to) will need to commit to: 

  • creating or enhancing habitat 
  • managing the habitat for at least 30 years 

The legal agreement must be in writing and signed by all parties (‘executed as a deed’).

You should get legal advice before entering a legal agreement. You will have to pay for any legal costs. 

Planning obligation 

A planning obligation agreement is between landowners and their LPA. The LPA will be responsible for enforcing the agreement. 

Conservation covenant agreement 

A conservation covenant agreement is between landowners and a responsible body. This type of legal agreement gives you more flexibility over who the agreement is with. 

We will publish a list of responsible bodies soon. 

Who can enter into a legal agreement for BNG BNG 

Land managers 

You can enter a legal agreement if you: 

  • are the landowner 
  • have a lease on the land that is at least the same length as the legal agreement 

If your lease is shorter, you’ll need to include the freeholder in your legal agreement. 

Your legal agreement will not replace any previous property rights. 


If the off-site gain is secured with a legal agreement by the landowner, the developer does not need to enter a legal agreement.  

If the developer is making: 

  • off-site gains on their own land that’s outside the development site, they must secure these gains with a legal agreement 
  • significant on-site gains, they need to enter a legal agreement as the landowner (the LPA might also need to be involved in this legal agreement)

Find out more about securing on-site gains with a legal agreement

LPAs and responsible bodies 

LPAs and responsible bodies should: 

LPAs and responsible bodies should not enter into an agreement if they do not think the landowner will meet their obligations.

How long your legal agreement must last 

Your legal agreement must last at least 30 years from finishing the habitat improvement. If you’re securing: 

  • on-site gains, your legal agreement starts from the date you complete the development 
  • off-site gains, your legal agreement starts from the date you finish the habitat enhancement  

You need to include how long it will take to create or enhance the habitat (for example, one year). This will help you to set an accurate end date for the legal agreement. 

You must meet your habitat condition targets for at least the length of your agreement. 

What to include in your legal agreement 

You’ll need to provide detailed information on your planned biodiversity habitat enhancements for the site (for example, create 2 hectares of neutral grassland in moderate condition).  

You may also include what specific actions you’ll take to achieve the habitat enhancements (for example, sow a seed mix or carry out bi-annual cuts). 

You’ll also need to agree who is responsible for: 

  • creating or enhancing the habitats 
  • managing and monitoring the habitats 

You can sub-contract the habitat work to a third party, but the legal agreement sets out who is responsible. You cannot include a subcontractor in the legal agreement. Only the landowner, LPA or responsible body can be responsible.

You can provide a detailed schedule of management and monitoring in a Habitat Management Monitoring Plan (HMMP)

You can view example legal agreements from the Planning Advisory Service. 

How you’ll allocate habitat enhancements 

You’ll need to agree: 

  • how you’ll allocate the enhancements (for example, to one or more developments) 
  • who will register the enhancement and any allocation 

Find out how to record the allocation of off-site units (land managers). 

Find out how to record the allocation of off-site units to your development (developers). 

Habitat location 

You’ll need to: 

  • identify the land where you’ll be creating or enhancing the habitat 
  • give the planned start date and expected completion date of the habitat creation or enhancement

What you’ll need to agree with your LPA or responsible body 

You’ll need to agree: 

  • how you’ll monitor the biodiversity gain site, including a schedule and how to access the land 
  • an end date that is at least 30 years from when you complete creating or enhancing the habitat 
  • any consent or licences that you need 
  • what actions the LPA or responsible body can take if you do not meet your obligations 
  • what actions you will take if the habitat enhancement does not go as planned 
  • how you will make permitted changes or manage disputes 
  • any funding arrangements (for example, for ongoing monitoring) and a payment schedule 
  • the statutory biodiversity metric 

If the habitat or enhancement is within the wildlife consultation area of an aerodrome, you must agree that it does not harm aircraft operations.  

You’ll need to agree that the relevant aerodrome: 

  • was notified of the proposed agreement 
  • had the opportunity to assess for potential hazards to aircraft operations 
  • is satisfied with the risk to aviation safety

What happens if you do not meet the terms of the legal agreement 

If you do not maintain the biodiversity gains in your legal agreement, the appropriate body will take enforcement action. 

If you have secured your on-site or off-site gains with a:

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Published 29 November 2023
Last updated 1 December 2023 + show all updates
  1. Added information about aerodrome safety.

  2. First published.