Biodiversity Net Gain Changes 6 August 2026: New 0.2 Hectare Exemption Explained

Last updated: August 14, 2026

Quick Answer: The Biodiversity Net Gain changes of 6 August 2026 introduced a new 0.2 hectare de minimis exemption, removing the previous small-sites and self-build exemptions and replacing them with a single area-based threshold. Developers, landowners, and planning consultants working on minor schemes in England need to understand exactly what qualifies, what evidence is required, and where the new rules create both opportunities and risks.

Key Takeaways

• From 6 August 2026, any development affecting less than 0.2 hectares of habitat is exempt from mandatory BNG, provided no priority habitat is present on the site.
• The self-build and custom-build exemption has been removed. Self-builders may now only rely on the new 0.2 ha threshold.
• For minor development, developers no longer need to demonstrate that onsite BNG units have been considered before turning to registered offsite units.
• Nationally Significant Infrastructure Projects (NSIPs) will not be subject to mandatory BNG until 2 November 2026, delayed from the original timetable.
• Temporary development lasting five years or less is now exempt from mandatory BNG requirements.
• Priority habitat on a site overrides the 0.2 ha exemption entirely, a habitat survey remains essential before relying on it.
• Defra announced these changes on 14 July 2026; they came into force on 6 August 2026.
• Local Planning Authorities (LPAs) and ecologists must update their validation checklists and pre-application advice processes accordingly.

What Is Biodiversity Net Gain and Why Does It Matter?

Biodiversity Net Gain (BNG) is a planning requirement in England that obliges developers to leave biodiversity in a measurably better state than before development. Under the Environment Act 2021, most planning permissions must deliver at least a 10% net gain in biodiversity units, calculated using the Defra Biodiversity Metric.

BNG matters because England has lost significant proportions of its wildlife habitats over the past century. The mandatory framework, which became law for major development in February 2024 and for small sites in April 2024, creates a direct link between development consents and ecological outcomes. Developers either deliver units onsite, purchase registered offsite units, or buy statutory biodiversity credits from government as a last resort.

What Changed on 6 August 2026 Under the New BNG Rules?

On 14 July 2026, Defra announced a package of amendments to the BNG framework. Those amendments came into force on 6 August 2026. The Biodiversity Net Gain changes 6 August 2026 new 0.2 hectare exemption is the headline measure, but four other significant changes accompanied it.

Summary of changes effective 6 August 2026:

Wealden District Council's updated guidance, published shortly after the Defra announcement, was among the first LPA resources to reflect these changes and provides a useful practical reference for applicants in the South East.

The 0.2 Hectare Exemption: What It Covers and How to Use It

The new 0.2 ha exemption means that a development application is exempt from mandatory BNG if the total area of habitat affected is less than 0.2 hectares (2,000 square metres). This replaces the previous small-sites exemption, which used a dwelling-count threshold rather than a habitat-area measurement.

Conditions that must all be met:

• The total habitat area affected by the development footprint is less than 0.2 ha.
• No priority habitat (as defined in the Habitats Regulations and the Defra priority habitats inventory) is present within the development footprint.
• The development is not an NSIP.
• The development is not a householder application that would otherwise be exempt on separate grounds.

Critical point: The 0.2 ha threshold applies to the area of habitat affected, not the total site area. A one-hectare brownfield site with only 0.15 ha of measurable habitat could qualify. Conversely, a 0.18 ha garden with ancient hedgerows classified as priority habitat would not qualify.

Which Projects Are Exempt from BNG Now?

As of 6 August 2026, the following categories are exempt from mandatory BNG:

• Development affecting less than 0.2 ha of habitat (no priority habitat present).
• Temporary development with a planning permission duration of five years or less.
• Householder applications (this exemption predates August 2026 and remains in place).
• Permitted development (where no full planning permission is required).

Not exempt:

• Any site containing priority habitat, regardless of size.
• NSIPs (mandatory BNG applies from 2 November 2026).
• Any development where the LPA has imposed a BNG condition through local policy.

How to Calculate Whether Your Project Qualifies for the 0.2 Hectare Exemption

Qualifying for the exemption requires a two-step assessment. First, measure the habitat area affected. Second, confirm no priority habitat is present.

Step-by-step process:

1. Commission a Phase 1 Habitat Survey (or Preliminary Ecological Appraisal) to map all habitats within the development footprint.
2. Calculate the total area of habitat using the Defra Biodiversity Metric habitat categories.
3. Check the Natural England Priority Habitat Inventory and the site survey results for any priority habitat.
4. If total habitat area is below 0.2 ha and no priority habitat is present, the exemption applies.
5. Record the evidence and submit it with the planning application or notify the LPA as required.

Common mistake: Developers sometimes measure the plot boundary rather than the habitat area. The exemption threshold relates specifically to habitat, so a site with extensive hardstanding may have a much smaller qualifying habitat area than its total footprint suggests.

Self-Build and Custom-Build: What the Removal of the Old Exemption Means

Before 6 August 2026, self-build and custom-build projects had a dedicated exemption from BNG requirements. That exemption has now been removed. Self-builders and custom-builders may only claim exemption if their project qualifies under the new 0.2 ha habitat-area threshold.

In practice, many self-build plots are small enough to fall below 0.2 ha of habitat, particularly on infill or brownfield land. However, self-builders on larger rural plots, or those developing land with hedgerows, woodland edges, or grassland, may find they no longer qualify for any exemption and must now comply with mandatory 10% BNG.

Advice for self-builders: Do not assume the old exemption still applies. Commission a Preliminary Ecological Appraisal before submitting any planning application to confirm whether the 0.2 ha threshold is met.

Minor Development: New Flexibility on Onsite vs Offsite Units

Previously, developers of minor schemes had to demonstrate that onsite BNG delivery had been fully considered before registered offsite units could be used. From 6 August 2026, this sequential requirement no longer applies to minor development.

Onsite habitat creation and registered offsite biodiversity units are now assessed at the same stage of the planning process. This change gives small developers and their ecologists more flexibility to design BNG strategies that are genuinely deliverable, rather than forcing onsite solutions that may be impractical on constrained urban sites.

What this means in practice: A minor residential scheme on a tight brownfield plot can now propose a combination of offsite units and limited onsite planting from the outset, without having to justify why full onsite delivery was not possible first.

NSIP Mandatory BNG: Delayed to 2 November 2026

Nationally Significant Infrastructure Projects were expected to become subject to mandatory BNG earlier in 2026. Defra's 14 July 2026 announcement confirmed a further delay, with mandatory BNG for NSIPs now commencing on 2 November 2026.

NSIP promoters and their ecological consultants should use the remaining period to ensure their Biodiversity Metric assessments and BNG strategies are ready for submission. The delay does not remove the requirement, it simply provides additional preparation time.

Temporary Development: The New Five-Year Exemption

Development that is genuinely temporary, where the planning permission is granted for a period of five years or less, is now exempt from mandatory BNG. This is a new and distinct exemption, separate from the 0.2 ha threshold.

The exemption is intended to reduce the regulatory burden on short-term uses such as construction compounds, temporary event infrastructure, and time-limited agricultural structures. It does not apply to development that is described as temporary but where the planning permission does not specify a clear end date or restoration condition.

What This Means for Developers

The Biodiversity Net Gain changes 6 August 2026 new 0.2 hectare exemption creates genuine relief for small and minor schemes, but introduces new risks for those who misapply it.

Opportunities:

• Smaller residential and commercial schemes below 0.2 ha of habitat can proceed without a BNG strategy, reducing costs and programme time.
• Minor development schemes gain flexibility to blend onsite and offsite BNG delivery from the start.
• Temporary projects of five years or less avoid BNG compliance entirely.

Risks:

• Relying on the exemption without a habitat survey exposes developers to enforcement risk if priority habitat is later identified.
• Self-builders who assumed the old exemption still applied may face unexpected BNG obligations.
• Sites just above 0.2 ha of habitat cannot use the exemption and must deliver full 10% BNG.

What This Means for LPAs and Ecologists

LPAs need to update their validation checklists to reflect the new exemption categories. Applications claiming the 0.2 ha exemption should be required to submit evidence, typically a signed Preliminary Ecological Appraisal or habitat survey confirming the area and absence of priority habitat.

Ecologists advising on small sites should:

• Confirm habitat area calculations are based on Defra Metric habitat categories, not plot boundaries.
• Check the Natural England Priority Habitat Inventory as a baseline, but always verify on the ground.
• Advise clients that the exemption is self-certified but challengeable, robust survey evidence protects both the developer and the LPA.
• Update standard report templates to include an explicit BNG exemption assessment section.

BNG Old Rules vs New Rules: A Direct Comparison

Do I Still Need a Biodiversity Survey for Projects Under 0.2 Hectares?

Yes. The exemption is not automatic and cannot be claimed without evidence. A Preliminary Ecological Appraisal (PEA) or Phase 1 Habitat Survey is needed to confirm two things: that the habitat area affected is below 0.2 ha, and that no priority habitat is present.

Submitting a planning application and simply asserting the exemption applies, without supporting survey evidence, is likely to result in an invalid application or a planning condition requiring further ecological assessment. The cost of a PEA is modest relative to the risk of delay.

Is the 0.2 Hectare Exemption Available in Scotland and Wales?

No. The mandatory BNG framework under the Environment Act 2021 applies in England only. Scotland and Wales have separate legislative frameworks for biodiversity and ecological net gain. The Biodiversity Net Gain changes 6 August 2026 new 0.2 hectare exemption, and all the associated rule changes, apply exclusively to planning applications in England.

Common Mistakes with the New BNG Exemption

• Measuring the wrong area: Using total site area rather than habitat area to assess the threshold.
• Ignoring priority habitat: Assuming a small site has no priority habitat without a survey.
• Self-builders assuming continuity: Relying on the old self-build exemption that no longer exists.
• Temporary development without a fixed end date: Claiming the five-year exemption for development where the permission does not specify a clear restoration or cessation date.
• Not notifying the LPA: Some LPAs require formal notification or a signed declaration when claiming an exemption, check local validation requirements.

Next Steps: Commission a Preliminary Ecological Appraisal Early

The single most effective action any developer, landowner, or planning consultant can take right now is to commission a Preliminary Ecological Appraisal before submitting a planning application. A PEA will:

• Confirm whether the 0.2 ha habitat-area threshold is met.
• Identify any priority habitats that would override the exemption.
• Provide the evidence base needed to support an exemption claim or to scope a BNG strategy if one is required.
• Flag any protected species issues that need addressing alongside BNG.

Early ecological input avoids costly delays at validation and reduces the risk of conditions being imposed mid-determination. For projects that do not qualify for the exemption, early survey work also means the Biodiversity Metric assessment can be completed in time to inform the design, rather than being retrofitted to a fixed scheme.

Frequently Asked Questions

Q: Does the 0.2 ha exemption apply automatically, or do I need to apply for it?
The exemption is self-certified, not applied for. However, developers must be able to evidence the qualifying conditions, specifically habitat area below 0.2 ha and absence of priority habitat, when submitting a planning application. Most LPAs will require a habitat survey or PEA to support the claim.

Q: My site is 0.22 ha of habitat. Can I reduce the scheme to qualify for the exemption?
Technically, if the development footprint can be genuinely reduced so that the habitat area affected falls below 0.2 ha, the exemption may apply. However, this must reflect a real change to the scheme, not a paper exercise. An ecologist should confirm the revised habitat area calculation.

Q: I'm a self-builder. Do I still have any BNG exemption?
Yes, but only if your project affects less than 0.2 ha of habitat and no priority habitat is present on site. The dedicated self-build exemption was removed on 6 August 2026.

Q: What counts as priority habitat for the purposes of the exemption?
Priority habitats are those listed in the UK Biodiversity Action Plan and the Natural England Priority Habitat Inventory. Common examples include ancient woodland, lowland meadow, hedgerows, blanket bog, and coastal habitats. An ecologist conducting a PEA will identify these during the survey.

Q: Does the five-year temporary development exemption apply to construction compounds?
Yes, provided the planning permission explicitly limits the use to five years or less and includes a restoration condition. If the permission does not specify a clear end date, the exemption is unlikely to apply.

Q: When does mandatory BNG apply to NSIPs?
Mandatory BNG for Nationally Significant Infrastructure Projects comes into force on 2 November 2026, following the delay announced by Defra on 14 July 2026.

Conclusion

The Biodiversity Net Gain changes of 6 August 2026 represent a meaningful recalibration of the mandatory BNG framework in England. The new 0.2 hectare de minimis exemption provides genuine relief for small schemes, the removal of the self-build exemption closes a loophole, and the new flexibility for minor development removes an unhelpful sequential test. The five-year temporary development exemption adds further proportionality to the system.

However, none of these changes reduce the need for early ecological input. Priority habitat overrides the exemption entirely, and the consequences of misapplying it, invalid applications, enforcement action, or late-stage redesign, are far more costly than a timely Preliminary Ecological Appraisal. Developers, landowners, and planning consultants who act early will be best placed to use the new rules to their advantage.

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