The BNG Process

Submission and Assessment of an Application

Planning applications for new development (unless exempt) are now expected to deliver new improved standards for biodiversity.

Consequently, updated national validation requirements mean that applications should include additional supporting documentation such as a completed Statutory Biodiversity Metric or Small Sites Metric; and a Habitat Plan that shows the location and extent of existing on-site habitats.

Although BNG is essentially a pre-commencement condition, it must be considered throughout the planning process and cannot be left until post-determination. Applicants should demonstrate how the biodiversity gain hierarchy, and the Interim Strategic Significance Guidance have been considered when preparing and designing their proposal.

When assessing an application, the Council must be confident that the proposed development is capable of achieving at least 10% BNG. Therefore, in addition to national requirements, it has also updated its local validation checklist to include the submission of some post-development biodiversity information as part of the minimum requirements to validate a planning application that is subject to the General Biodiversity Gain Condition.

Securing Significant and Off-site Gains

Where biodiversity gains on development sites are deemed ‘significant’ and/or where delivery of BNG is proposed off-site, applicants are required to legally secure these ‘gains’ for a minimum of 30 years by either a S106 agreement with the Council or alternatively a conservation covenant with an approved Responsible Body.

Should a S106 agreement (or conservation covenant) be necessary, then either of these must be completed and signed prior to an application to discharge the general biodiversity gain condition. Although a S106 (where BNG is the only obligation) doesn’t need to be signed prior to a planning permission being granted, drafting of the agreement can commence earlier where the case officer has sufficient confidence in the BNG Strategy being proposed, so as to avoid delays post permission. 

Significant on-site gains

Significant on-site gains refer to areas of habitat creation and/or enhancements which contribute significantly towards the proposed development’s BNG, relative to the biodiversity value before development.

DEFRA have published guidance which includes examples of what could be considered as “significant on-site biodiversity gains”. As this national guidance provides a very broad definition, this guidance has been developed by KCC to provide Kent Local Planning Authorities (LPAs) and planning applicants with a consistent approach for defining “significant on-site habitat” in Kent and Medway.

Off-site gains

Off-site gains refer to habitat creation and/or enhancements that are proposed to be delivered on land outside of the application's red line boundary, regardless of proximity or ownership. This does include where biodiversity units are being purchased from a registered Habitat Bank.

The General Biodiversity Gain Condition

The Town and Country Planning Act has been amended to make every grant of planning permission deemed to have been granted subject to the following General Biodiversity Gain Condition:

The development may not be begun unless: 
(a) a biodiversity gain plan has been submitted to the planning authority; and 
(b) the planning authority has approved the plan.

The purpose of the general biodiversity gain condition is to secure the ‘biodiversity objective’, which requires the post-development biodiversity value to exceed the pre-development biodiversity value of the on-site habitat by at least 10%.

Biodiversity net gain can be achieved through habitat creation or enhancement on-site and off-site; the purchase of biodiversity units from a habitat bank; or as a last resort through the purchase of statutory credits; or a mixture of these.

The Decision Notice

The General Biodiversity Gain Condition has a separate legal basis in contrast to other planning conditions and will apply to all planning permissions, unless exempt.  The general biodiversity condition will not appear on the decision notice along with the list of planning conditions imposed on the application, rather it will be referenced in an informative note.

The general biodiversity gain condition cannot be varied or removed by an application under section 73 of the Town and Country Planning Act. It also cannot be discharged as part of the grant of planning permission.

Discharging the General Biodiversity Condition

Following grant of planning permission, a development subject to the general biodiversity condition cannot be commenced until it has been successfully discharged. This requires a biodiversity gain plan to be submitted to and approved by the council.  

Biodiversity Gain Plans

To discharge the general biodiversity condition, a completed biodiversity gain plan which sets out how the biodiversity gain objective of at least a 10% gain will be achieved, must be submitted along with the following supporting information:

• A completed statutory biodiversity metric;
• Pre-development and post-development plans showing the location of on-site habitat; 
• A compensation Plan if the development affects irreplaceable habitats;
• Biodiversity net gain register reference numbers if they’re using off-site units (purchased from a Habitat Bank);
• Proof of purchase if buying statutory biodiversity credits.
• A Habitat Management and Monitoring Plan (HMMP) setting out significant on-site gains will be managed and monitored. 

The plan must be submitted in writing, no earlier than the day after planning permission has been granted. There is no separate application form to be completed, but there will be an additional statutory £145 fee. Biodiversity gain plans should be submitted citing the planning application reference to which it relates.

A developer may submit a draft biodiversity gain plan alongside the planning application for information and discussion with the planning officer prior to determination of the application, although this is not a validation requirement. 

Templates for the Biodiversity Gain Plan and for Habitat Management and Monitoring Plan have been created by DEFRA and Natural England. Links to these can be found on the Validation, Guidance and Tools page.

Phased Biodiversity Gain Plans

Where development is to be delivered in phases, the requirement for biodiversity gain plans differs. Instead of the standard approach as detailed above:

• An Overall Biodiversity Gain Plan must be submitted to and approved by the council before any development can be begun; 
• A Biodiversity Gain Plan for each phase must be submitted to and approved by the council before the development of that phase can be begun.

This recognises that phased development can often be implemented over a long period of time. The purpose of the Overall Biodiversity Gain Plan is to set a clear upfront framework for how the biodiversity gain objective of at least a 10% gain is expected to be met across the entire development.

The Biodiversity Gain Plan for each phase will then subsequently set out a phase’s contribution to biodiversity net gain and track progress towards the achieving the biodiversity gain objective.

Habitat Monitoring

Developers must maintain significant on-site and all off-site habitats that they create or enhance for a minimum of 30 years. These habitats will be subject to a monitoring schedule that ensures they achieve the target condition and distinctiveness that was stated in the Biodiversity Metric. 

The 30-year monitoring period will commence once the habitat(s) have been implemented, and a ‘Certificate of Completion’ issued by the Council. The frequency of monitoring will be agreed as part of an approved Habitat Management and Monitoring Plan (HMMP) and reflected in the S106 or conservation covenant. Where habitats are identified through monitoring as not meeting the expected target condition or distinctiveness, remedial management strategies may need to be prepared, approved and actioned to address any deficiencies.

A monitoring fee will be payable with the submission of each monitoring report to the Council for approval. The fee covers the costs of Ashford Borough Council’s and Kent Ecological Advice Service’s time and resources to process and review the monitoring report. 

The table below sets out the baseline monitoring fees for inclusion in S106 agreements signed in 2025/26; and will be subject to indexation using the Retail Prices Index (RPI).

 *An alternative monitoring schedule may be necessary and should be determined as part of the agreed HMMP.

** The number of site visits to be determined as part of the agreed HMMP.