Comply with Biodiversity Net Gain

Biodiversity Net Gain is a condition applying to most planning permissions in England. It requires developers to use the statutory biodiversity metric to calculate the pre-development biodiversity value of the onsite habitat and demonstrate that the development will achieve at least a 10% increase in biodiversity value. Biodiversity Net Gain is based on a set of principles and rules which our service complies with at all stages.

Biodiversity Net Gain applies to most planning permissions in England, but certain types of development are exempt. The principal exemptions are summarised below.

The following rules apply to planning applications made on or after 6 August 2026:

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• Development on a site of 0.2 hectares or below. BNG does not apply where the total site area within the planning application red-line boundary is 0.2 hectares—2,000 square metres—or below. This exemption cannot be used where the development negatively impacts priority habitat located onsite.
• The red-line boundary should accurately identify all land forming part of the proposed development. The exemption is based on the total area within that boundary, rather than only the building footprint or the area of habitat affected.
• De minimis development. BNG does not apply where the development does not negatively impact any priority habitat onsite and impacts less than 25 square metres of onsite habitat with a biodiversity value greater than zero and less than five metres of onsite linear habitat, such as a hedgerow.
• Applicants must state in their planning application why they consider this exemption applies and should provide sufficient evidence to support their justification. Where the position cannot be clearly demonstrated through the application plans and description, government guidance strongly encourages applicants to provide completed pre-development and post-development metric calculations and clear plans identifying the nature and extent of the habitat affected.

• Temporary development. BNG does not apply where the whole development is temporary and planning permission is granted for five years or less. This exemption cannot be used where the development negatively impacts priority habitat located onsite.
• Householder development. Development that is the subject of a householder application, as defined in article 2(1) of the Town and Country Planning (Development Management Procedure) (England) Order 2015.
• Development granted planning permission by a development order under section 59 of the Town and Country Planning Act 1990, including development permitted through permitted development rights.
• Urgent Crown development granted permission under section 293A of the Town and Country Planning Act 1990.
• Development of a biodiversity gain site. Development which is undertaken solely or mainly for the purpose of fulfilling, in whole or in part, the biodiversity gain condition which applies in relation to another development.

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Specified development forming part of, or ancillary to, the high-speed railway transport network.

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The previous exemption for qualifying self-build and custom-build development does not apply to planning applications made on or after 6 August 2026. It may continue to apply where the original planning application was made before that date, including to a subsequent variation where the original planning permission was exempt.

Transitional exemptions may also continue to apply to planning applications made before mandatory BNG commenced and to certain subsequent variations of those permissions.

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Use the Joe’s Blooms BNG Exemption Checker to identify the assessment route that may apply to your development.

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It’s very important that baseline assessments are done by the right person. You should not use automated solutions but base information on site surveys. For large sites or offsites, that should be a qualified ecologist. If it’s a small site, then it should be done by a ‘competent person’.

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The Joe’s Blooms Biodiversity Net Gain Tool helps you identify the right person to undertake the baseline assessment and can connect you with people trained in habitat assessment where additional support is needed. For many small sites, the competent person may be the project manager or architect.

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‍Page Guide: Competent Person | Joe's Blooms Help Center

The Small Site Metric (SSM) is a special version of the Biodiversity Net Gain Metric that can be used if:

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• The site is under 10,000 sqm/1 hectare/2.471 acres
• Does not meet the legal definition of a "major development"
• Does not have any priority habitat within the red line boundary.

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The Small Site User Guide contains detailed information.

While satellite imagery and AI can help with Biodiversity Net Gain assessments, they are not substitutes for appropriate onsite surveys. Baseline habitat assessments must be completed by a ‘competent person’ or, where required, a qualified ecologist. Condition assessments must also be provided where applicable to support judgements about the condition of the baseline habitat.

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