Last updated: August 5, 2026
Quick Answer: From 6 August 2026, four significant changes to mandatory Biodiversity Net Gain (BNG) take effect in England under SI 2026 No. 790. A new small-site exemption removes BNG obligations for developments of 0.2 hectares or less (provided no on-site priority habitats are affected), a temporary-development exemption covers permissions of five years or less, the self-build and custom-build exemption is abolished, and the statutory hierarchy for minor developments is relaxed so that off-site gains now sit on equal footing with on-site creation. The Biodiversity Net Gain changes 6 August 2026 developers new exemptions represent the most significant recalibration of the BNG regime since it became mandatory for major developments in February 2024.
Key Takeaways
- Developments of 0.2 hectares (2,000 m²) or less are exempt from mandatory BNG from today, unless they affect on-site priority habitats.
- Temporary planning permissions of five years or less are also exempt from BNG requirements.
- Self-build and custom-build projects lose their previous exemption and must now comply with mandatory BNG.
- For minor developments, off-site biodiversity gains are now treated equally to on-site habitat creation, the strict statutory hierarchy no longer applies.
- Nationally Significant Infrastructure Projects (NSIPs) will face mandatory BNG from November 2026, confirmed by government.
- The statutory instruments were laid before Parliament on 13 July 2026 and come into force today. [1]
- Priority habitat on a site, however small, can override the small-site exemption entirely.
- Developers should commission a baseline habitat survey before assuming any exemption applies.
What Is Biodiversity Net Gain and Why Does It Matter?
Biodiversity Net Gain is a legal requirement under Schedule 7A of the Town and Country Planning Act 1990 (as inserted by the Environment Act 2021) that compels developers to leave biodiversity in a measurably better state than before development. In practical terms, this means achieving at least a 10% net gain in biodiversity units compared to the pre-development baseline, measured using the Defra biodiversity metric.
BNG matters because England has lost significant proportions of its wildlife habitats over the past century. The policy attempts to reverse that trend by making habitat improvement a condition of planning consent rather than an optional add-on. For a fuller grounding in the framework, see Biodiversity Net Gain Explained.
The gain can be delivered on-site, off-site through a registered habitat bank, or, as a last resort, through statutory biodiversity credits purchased from government. For a breakdown of those delivery routes, the guide to off-site or on-site BNG delivery covers the trade-offs in detail.
Biodiversity Net Gain Changes August 2026: What's New for Developers?
Four confirmed changes take effect today under SI 2026 No. 790, which was laid before Parliament on 13 July 2026. [1][8] Each change affects a different category of development, and collectively they reshape who must comply, how gains can be delivered, and which projects remain fully in scope.
Change 1: New Small-Site Exemption (≤0.2 Hectares)
Developments on sites of 0.2 hectares or less, roughly 40m x 50m, or about one-third of a football pitch, are now exempt from mandatory BNG, provided the development does not reduce the biodiversity value of any on-site priority habitat. [3][4]
This is a significant relief for small housebuilders and infill developers. However, the priority habitat caveat is critical: if a hedgerow, traditional orchard, or any other Defra-listed priority habitat sits within the red-line boundary, the exemption does not apply regardless of site size. [3][7] Crossman Ecology notes that even very small schemes may still need a full BNG assessment if priority habitats are present on site. [3]
Change 2: New Temporary-Development Exemption
Planning permissions granted for five years or less are now exempt from mandatory BNG. [2][8] This primarily benefits temporary structures, short-term infrastructure, and pop-up developments. The rationale is that a 30-year habitat management obligation (required under BNG) is disproportionate for a development that will be reversed within five years.
Change 3: Removal of the Self-Build and Custom-Build Exemption
Previously, self-build and custom-build dwellings were exempt from BNG. That exemption is removed from today. [6][8] Any self-builder or custom-builder whose application is determined on or after 6 August 2026 must now deliver the mandatory 10% biodiversity net gain alongside any other planning conditions.
This is the most significant change for individual homebuilders. A self-builder on a site larger than 0.2 hectares, or one that affects priority habitat, faces the full BNG obligation. Self-builders on sites of 0.2 hectares or less that do not affect priority habitats may still qualify for the new small-site exemption, but this must be confirmed through a proper habitat assessment.
Change 4: Relaxed Statutory Hierarchy for Minor Developments
Under the original BNG regime, developers were required to follow a strict hierarchy: first attempt on-site gains, then off-site, and only use statutory credits as a last resort. From today, minor developments benefit from a relaxed version of this hierarchy in which off-site gains are treated as equally valid as on-site habitat creation. [2][9]
This gives smaller developers greater flexibility. Rather than being compelled to shoehorn habitat creation onto constrained urban plots, they can now use registered off-site habitat banks or buy biodiversity units from the market without having to justify why on-site delivery is impractical.
Which Developers Are Exempt from Biodiversity Net Gain Requirements?
After today's changes, the following categories are exempt from mandatory BNG:
| Category | Exemption Condition |
|---|---|
| Small sites (≤0.2 ha) | No on-site priority habitats affected [3][4] |
| Temporary permissions | Duration of 5 years or less [2][8] |
| Householder applications | Exempt (unchanged from original rules) |
| Permitted development | Exempt (unchanged from original rules) |
| De minimis developments | Less than 25 m² of habitat impact (unchanged) |
Self-build and custom-build projects are no longer exempt as of today. [6][8]
For a comprehensive list of project types and their exemption status, see the guide to exempt projects.
How Do the New Exemptions Affect Small Housing Developments?
Small housing developers, particularly those building one to five units on tight urban or suburban plots, stand to benefit most from the 0.2-hectare small-site exemption. A single dwelling on a 0.15-hectare plot with no priority habitats on site is now exempt from BNG entirely, removing the cost and administrative burden of a biodiversity metric calculation, a biodiversity gain plan, and a 30-year management agreement.
The practical test is straightforward:
- Is the net development area 0.2 ha or less?
- Does the site contain any Defra-listed priority habitats?
If the answer to question 1 is yes and question 2 is no, the exemption applies. If there is any doubt about priority habitats, and hedgerows, ponds, and semi-improved grassland are frequently overlooked, a Phase 1 habitat survey is the only reliable way to confirm eligibility. [3][7]
Common mistake: Assuming a small garden plot is free of priority habitats without checking. A single mature hedgerow along a boundary can bring a site back into scope.
Which Projects Are Still Required to Do Biodiversity Net Gain After August 2026?
The majority of developments in England remain subject to mandatory BNG. Projects still fully in scope include:
- Major residential and commercial developments (unchanged)
- Minor developments on sites larger than 0.2 ha
- Any development, regardless of size, that affects on-site priority habitats [3][7]
- Self-build and custom-build projects (now in scope from today) [6][8]
- Nationally Significant Infrastructure Projects from November 2026 [5]
Developers working on larger schemes should review the 8 BNG points on planning your project to ensure their pre-application process accounts for the updated rules.
What's Coming Next: BNG for Nationally Significant Infrastructure Projects
The government has confirmed that mandatory BNG will apply to Nationally Significant Infrastructure Projects (NSIPs) from November 2026. [5] NSIPs include major roads, rail, energy, and water infrastructure that are consented through the Development Consent Order process rather than the standard planning system.
This is a substantial expansion of the BNG regime. NSIP promoters, typically large utilities, transport authorities, and energy companies, should begin baseline habitat surveys and biodiversity metric assessments now if they have not already done so. The scale of habitat impact associated with NSIPs means that statutory biodiversity credits alone are unlikely to be sufficient, and off-site habitat banking arrangements will need to be secured well in advance.
How Do I Calculate Biodiversity Net Gain for My Project?
BNG is calculated using the Defra biodiversity metric (currently version 4.0), which assigns a unit value to habitats based on their type, condition, and distinctiveness. The calculation compares pre-development habitat units against post-development habitat units (including any new or enhanced habitats), and the result must show a net gain of at least 10%.
The key steps are:
- Commission a baseline habitat survey (Phase 1 and, where needed, Phase 2).
- Apply the Defra metric to quantify existing biodiversity units.
- Design the development to retain and enhance habitats where possible.
- Calculate post-development units, including any proposed new habitats.
- Identify any shortfall and determine whether it will be met on-site, off-site, or via statutory credits.
- Prepare a Biodiversity Gain Plan for submission with the planning application.
For a step-by-step walkthrough, see how to conduct a biodiversity impact assessment and the detailed guide on how to achieve 10% biodiversity net gain.
What's the Difference Between Biodiversity Net Gain and Habitat Banking?
Biodiversity Net Gain is the legal obligation, the requirement to achieve a 10% improvement in biodiversity units. Habitat banking is one of the mechanisms used to meet that obligation off-site.
A habitat bank is a registered site where a landowner creates, enhances, or restores habitats in advance of development, generating biodiversity units that can be sold to developers who cannot fully meet their BNG requirement on-site. The units are recorded on the national biodiversity gain sites register and are legally secured through a conservation covenant or planning obligation.
The distinction matters for cost planning: off-site units from a habitat bank are typically less expensive than statutory biodiversity credits purchased from government, but they require advance planning and availability in the relevant local area. Developers can buy biodiversity units through registered habitat banks, and landowners can sell biodiversity units to generate long-term income from their land.
Are There Penalties If Developers Don't Meet Biodiversity Net Gain Targets?
Yes. Failure to comply with mandatory BNG is a breach of planning conditions, which can result in enforcement action by the local planning authority, including stop notices, enforcement notices, and, in serious cases, prosecution. BNG compliance is a pre-commencement condition, meaning development cannot lawfully begin until the Biodiversity Gain Plan has been approved.
Additionally, the 30-year habitat management obligation attached to BNG sites is legally binding. Failure to maintain habitats in accordance with the approved management plan can also trigger enforcement action.
How Much Will Biodiversity Net Gain Cost Developers Now?
Costs vary considerably depending on site size, baseline habitat quality, and the delivery route chosen. The August 2026 changes reduce costs for eligible small-site developers by removing the BNG obligation entirely, but for projects that remain in scope, the cost components are:
- Ecological survey and metric calculation: typically £1,500,£5,000 for minor developments (estimate based on practitioner ranges; confirm with your ecologist).
- On-site habitat creation: variable, embedded in landscaping costs.
- Off-site biodiversity units: market-priced, varying by habitat type and location.
- Statutory biodiversity credits: government-set prices, generally the most expensive option and intended as a last resort.
For current statutory credit pricing, see the cost of biodiversity units and statutory credits guide.
The relaxed hierarchy for minor developments introduced today means that smaller developers can now access off-site unit markets more readily, which may reduce costs compared to the previous requirement to demonstrate on-site delivery first. [2][9]
What Developers Should Do Today
The Biodiversity Net Gain changes 6 August 2026 developers new exemptions take effect immediately. Here is what each group should do now:
Small-site developers (≤0.2 ha):
- Commission a Phase 1 habitat survey to confirm whether any priority habitats are present on site before assuming the exemption applies.
- If the site is clear of priority habitats, document this formally and retain the survey for the planning file.
- If priority habitats are present, proceed as if the full BNG obligation applies.
Self-builders and custom-builders:
- Accept that the previous exemption no longer exists for applications determined from today.
- Engage an ecologist early, ideally at pre-application stage, to assess the baseline and identify the most cost-effective route to 10% net gain.
- Consider whether the site qualifies for the new small-site exemption (≤0.2 ha, no priority habitats).
Minor development applicants:
- Take advantage of the relaxed statutory hierarchy by exploring off-site habitat bank options in parallel with on-site design, rather than treating off-site as a fallback.
NSIP promoters:
- Begin baseline ecological surveys immediately if not already underway.
- Engage with registered habitat banks to secure off-site unit agreements ahead of the November 2026 mandatory date. [5]
Ecologists and planners:
- Update client advice templates to reflect the removal of the self-build exemption.
- Familiarise yourselves with the transitional arrangements published by Defra on 14 July 2026. [1]
- Review the 8 things planners need to know about BNG for a practical planning-authority perspective.
Conclusion
The Biodiversity Net Gain changes 6 August 2026 developers new exemptions mark a meaningful recalibration of England's BNG regime. Small-site developers and those with temporary permissions gain genuine relief from a requirement that was, for the smallest schemes, disproportionately burdensome. At the same time, the removal of the self-build exemption closes a loophole and signals that government intends BNG to apply broadly across the planning system.
The key lesson from today's changes is that exemptions are conditional, not automatic. Priority habitats on even the smallest site can bring a development back into full BNG scope. The only way to confirm eligibility is through a proper habitat assessment by a qualified ecologist.
With NSIPs entering the mandatory BNG regime in November 2026, the scope of the policy will expand significantly before the year is out. Developers, landowners, and infrastructure promoters who act now, commissioning surveys, securing habitat bank agreements, and building BNG into project budgets from the outset, will be far better placed than those who treat compliance as an afterthought.
Frequently Asked Questions
Q: Does the 0.2-hectare exemption apply to the whole development or just the built footprint?
A: The 0.2-hectare threshold applies to the area of the development site within the red-line boundary, not just the built footprint. If the total site area exceeds 0.2 ha, the exemption does not apply even if the built area is smaller. [3][4]
Q: My self-build application was submitted before 6 August 2026. Am I affected?
A: The transitional arrangements published by Defra on 14 July 2026 set out how applications in progress are treated. Applications determined before 6 August 2026 under the old rules are unaffected. Applications determined on or after today are subject to the new rules, including the removal of the self-build exemption. Check the Defra transitional guidance for your specific circumstances. [1]
Q: What counts as a priority habitat for the purposes of the small-site exemption?
A: Priority habitats are those listed under Section 41 of the Natural Environment and Rural Communities Act 2006. Common examples include hedgerows, traditional orchards, semi-improved grassland, ponds, and ancient woodland. A Phase 1 habitat survey will identify whether any are present on site. [3][7]
Q: Can a minor development use statutory biodiversity credits instead of habitat banking?
A: Yes, statutory credits remain available as a last resort for any development that cannot meet its BNG requirement on-site or through off-site habitat banks. However, statutory credits are priced to make them the most expensive option deliberately, to incentivise genuine habitat creation. [2]
Q: When does BNG become mandatory for NSIPs?
A: The government has confirmed mandatory BNG for Nationally Significant Infrastructure Projects from November 2026. [5]
Q: Do the August 2026 changes affect Wales, Scotland, or Northern Ireland?
A: No. Mandatory BNG under the Environment Act 2021 applies to England only. Wales, Scotland, and Northern Ireland have separate devolved planning and environmental frameworks.
References
[1] Biodiversity Net Gain Amendments And Transitional Arrangements Published – https://defraenvironment.blog.gov.uk/2026/07/14/biodiversity-net-gain-amendments-and-transitional-arrangements-published/
[2] New Biodiversity Net Gain Exemptions From August 2026 What Developers Need To Know – https://www.footanstey.com/our-insights/articles-news/new-biodiversity-net-gain-exemptions-from-august-2026-what-developers-need-to-know/
[3] Biodiversity Net Gain Changes From 6 August 2026 What Developers Need To Know – https://www.crossmanecology.co.uk/biodiversity-net-gain-changes-from-6-august-2026-what-developers-need-to-know/
[4] Biodiversity Net Gain Small Sites Exemption 2026 – https://www.hampsteadarchitecture.co.uk/journal/biodiversity-net-gain-small-sites-exemption-2026/
[5] Biodiversity Net Gain For Nationally Significant Infrastructure Projects – https://www.gov.uk/government/consultations/biodiversity-net-gain-for-nationally-significant-infrastructure-projects
[6] Key Changes Confirmed To Biodiversity Net Gain – https://www.cla.org.uk/news/key-changes-confirmed-to-biodiversity-net-gain/
[7] New BNG Rules And Exemptions Apply From 6 August 2026 – https://cieem.net/new-bng-rules-and-exemptions-apply-from-6-august-2026/
[8] New Legislation Relating To Biodiversity Gain Including Amendments To The DMPO 2015 06 08 2026 – https://planningjungle.com/2026/07/21/new-legislation-relating-to-biodiversity-gain-including-amendments-to-the-dmpo-2015-06-08-2026/
[9] Biodiversity Net Gain (BNG) Update – https://www.twobirds.com/en/insights/2026/uk/biodiversity-net-gain-(bng)-update
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BNG Exemption Checker, 6 August 2026
— Select —
0.2 ha or less (≤2,000 m²)
More than 0.2 ha
— Select —
No priority habitats confirmed
Yes / unsure
— Select —
Temporary (≤5 yr permission)
Self-build / custom-build
Minor development
Major development
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