BNG Changes 6 August 2026 Small Sites Exemption: What Developers and Planners Need to Know

Last updated: August 22, 2026

Quick Answer: From 6 August 2026, planning applications for non-major developments where the entire site area within the red-line boundary is 0.2 hectares or less are exempt from mandatory biodiversity net gain requirements, provided the site contains no on-site priority habitat. This is the core of the BNG changes 6 August 2026 small sites exemption. Applications submitted before that date remain subject to previous BNG rules, regardless of site size. The 10% net gain requirement is unchanged for all other developments.

Key Takeaways

• The small sites exemption applies to non-major planning applications where the red-line site area is 0.2 ha or less and no on-site priority habitat is affected.
• Both conditions must be met simultaneously: area threshold and no priority habitat impact.
• Applications must be submitted on or after 6 August 2026 to benefit from the new exemption.
• The self-build and custom-build BNG exemption is removed from the same date; those projects now rely on the 0.2 ha test.
• Temporary planning permissions of five years or less gain a new exemption category.
• For non-major schemes that do not qualify for exemption, on-site and registered off-site BNG gains are treated with equal preference.
• Priority habitat protection is fully retained; a site loses the exemption the moment priority habitat is present or would be adversely affected.
• The 10% biodiversity net gain requirement remains unchanged for all non-exempt developments.
• Even exempt sites remain subject to protected species legislation and NPPF ecological requirements.
• Local planning authorities may still request short ecological statements to evidence exemption eligibility.

What Is the Small Sites Exemption in Biodiversity Net Gain?

The small sites exemption is a permanent feature of the BNG framework under the Environment Act 2021, introduced to reduce administrative burden on minor developments. It means that certain small, non-major planning applications are not required to demonstrate a 10% biodiversity net gain as a condition of planning permission.

The exemption has two linked conditions, both of which must be satisfied:

1. The total site area within the red-line boundary is no larger than 0.2 hectares.
2. The development does not impact any on-site priority habitat as defined under Section 41 of the Natural Environment and Rural Communities Act 2006.

If either condition fails, mandatory BNG applies in full. [3][8]

How Do the BNG Changes 6 August 2026 Small Sites Exemption Rules Work in Practice?

The BNG changes 6 August 2026 small sites exemption applies only to planning applications submitted on or after that date. Applications lodged before 6 August 2026 remain subject to the BNG rules in force at the time of submission, even if the site is under 0.2 ha. [6][11]

What this means for your application timeline:

• If you submitted before 6 August 2026 and your site is under 0.2 ha, the old rules still apply.
• If you submit on or after 6 August 2026 and your site meets both conditions, you are exempt from mandatory BNG.
• There is no retrospective application of the exemption.

Defra's guidance is explicit on this point: the submission date, not the decision date, determines which rules apply. [6]

Which Sites Qualify for the Small Sites Exemption Under New BNG Rules?

A site qualifies for the small sites exemption if it meets both the area and habitat conditions. Typical qualifying examples include single-plot infill housing, small commercial units, and modest conversions on brownfield land with no semi-natural vegetation. [4][7]

Sites that do NOT qualify, regardless of size:

• Any site above 0.2 ha (measured within the red-line boundary)
• Any site, however small, where priority habitat is present or would be adversely affected
• Major developments (10 or more dwellings, or commercial floorspace of 1,000 sq m or more)
• Nationally Significant Infrastructure Projects

Edge case to watch: A site of exactly 0.18 ha with a patch of lowland meadow (a Section 41 habitat) loses the exemption entirely. Priority habitat presence overrides the area test. [3][5]

What Size Threshold Triggers BNG Requirements After August 2026?

Any non-major development with a red-line site area above 0.2 ha must comply with full BNG requirements, regardless of what is being built. There is no sliding scale: the threshold is a hard cut-off at 0.2 ha. [3][8]

For major developments (broadly, 10 or more dwellings or 1,000 sq m or more of commercial floorspace), BNG has applied since February 2024 and continues unchanged. The 6 August 2026 changes do not alter the rules for major schemes.

Do Residential Developments Under 1 Hectare Need BNG After 6 August 2026?

Yes, unless they fall within the 0.2 ha small sites exemption. A residential development of, say, 0.5 ha is above the 0.2 ha threshold and must comply with full BNG requirements, including the 10% net gain target. The exemption threshold is 0.2 ha, not 1 ha. [3][8]

This is a common misunderstanding. The 1 ha figure sometimes cited in earlier guidance referred to a transitional threshold that predates the current framework. Under the rules in force from 6 August 2026, the operative threshold for non-major sites is 0.2 ha.

What Happened to the Self-Build and Custom-Build BNG Exemption?

The self-build and custom-build exemption is removed from 6 August 2026. Previously, self-build and custom-build projects could claim an automatic exemption from BNG based solely on their build type. That route no longer exists. [5][12]

From 6 August 2026, a self-build project must meet the same two-condition test as any other non-major development: site area of 0.2 ha or less, and no on-site priority habitat. If the self-build plot is larger than 0.2 ha, or if priority habitat is present, full BNG compliance is required.

This is a significant change for small housing projects that previously assumed automatic exemption based on self-build status. [5][12]

What Is the Temporary Planning Permission Exemption?

A new exemption category introduced from 6 August 2026 covers temporary planning permissions with a duration of five years or less. Developments authorised under such permissions are exempt from mandatory BNG requirements, reflecting the short-term and reversible nature of the land use change.

This exemption is distinct from the small sites exemption and applies based on the duration of the permission, not the site area. Developers seeking temporary permissions should confirm the five-year condition is clearly stated in the application and any grant of permission.

Equal Preference for On-Site and Off-Site BNG Gains: What Changes for Non-Major Schemes?

For non-major developments that do not qualify for the small sites exemption and must comply with BNG, the rules from 6 August 2026 give equal preference to on-site and registered off-site gains. Previously, there was a hierarchy that prioritised on-site delivery before off-site options could be used.

Under the updated approach, developers of non-major schemes can choose between on-site habitat creation and purchasing biodiversity units from a registered off-site gain site without having to justify why on-site delivery is not feasible first. This gives smaller developers greater flexibility in how they meet the 10% net gain requirement.

Statutory biodiversity credits (purchased from Natural England as a last resort) remain the third option and are not affected by this change. [8]

How to Calculate BNG for Sites That Don't Qualify for Exemption

Sites that fail either condition of the small sites exemption must demonstrate at least 10% biodiversity net gain using the Biodiversity Metric (currently Biodiversity Metric 4.0, published by Natural England). The calculation process applies equally to non-major and major schemes.

The core steps are:

1. Establish the pre-development habitat baseline using a site survey and the metric tool.
2. Calculate the post-development biodiversity unit value, including any on-site habitat creation or enhancement.
3. If on-site gains alone do not achieve 10%, use registered off-site gain sites or statutory biodiversity credits to make up the shortfall.
4. Secure the BNG through a planning condition or biodiversity gain plan approved by the local planning authority.

For non-major schemes, the equal-preference rule (see above) means step 3 can draw on off-site gains without a prior justification requirement. [8][9]

What Documentation Is Needed to Evidence Small Sites Exemption Eligibility?

To evidence the small sites exemption, developers should prepare and retain the following before submission: [2][9][11]

• A site area confirmation showing the red-line boundary measurement is 0.2 ha or less (typically from a scaled site plan).
• A priority habitat check using Natural England's Priority Habitat Inventory mapping, confirming no Section 41 habitat is present on site.
• A short written statement summarising both conditions and confirming the application qualifies for the exemption.

Local planning authorities may request supporting habitat plans or brief ecological statements even for exempt schemes, particularly where the site has semi-natural vegetation, long-established trees, or is adjacent to known priority habitat. [2][9] Developers should not assume that meeting the two conditions eliminates all ecological scrutiny.

Are Commercial Developments Under 1 Hectare Exempt from BNG Requirements?

A commercial development under 1 ha is not automatically exempt. The exemption threshold is 0.2 ha, not 1 ha, and it applies to non-major developments only. A commercial site of 0.15 ha with no priority habitat qualifies for the small sites exemption. A commercial site of 0.3 ha does not, regardless of its use class. [3][8]

Major commercial developments (1,000 sq m or more of floorspace) remain fully subject to BNG regardless of site area.

What Happens to Existing Planning Permissions Under the Old Small Sites Exemption?

Applications submitted before 6 August 2026 are governed by the rules in force at the time of submission. If a non-major application was submitted before that date and the site is under 0.2 ha, the previous BNG framework applies, which for most non-major sites meant a transitional exemption based on different criteria. [6][11]

Developers with live applications submitted before 6 August 2026 should not assume the new 0.2 ha exemption applies retrospectively. If in doubt, confirm the applicable rules with the relevant local planning authority or a qualified ecologist.

Priority Habitat Protection: What Stays the Same

Priority habitat protection is fully retained under the new rules. A site loses the small sites exemption the moment any on-site priority habitat is present or would be adversely affected by the development. This applies regardless of how small the site is or how minor the impact. [3][5][11]

Priority habitats are those listed under Section 41 of the Natural Environment and Rural Communities Act 2006 and include habitats such as lowland meadow, ancient woodland, and traditional orchard. Natural England's Priority Habitat Inventory is the primary mapping tool, but desk-study results should always be verified by a site survey where there is any doubt.

Even where the exemption applies, wider environmental protections remain in force, including protected species legislation and any ecological requirements imposed under the NPPF. [1][3]

BNG Changes 6 August 2026 Small Sites Exemption: Comparison Table

Scenario	Site Area	Priority Habitat?	BNG Required?
Small infill housing	0.15 ha	No	No (exempt)
Small infill housing	0.15 ha	Yes	Yes (10%)
Residential scheme	0.35 ha	No	Yes (10%)
Self-build plot	0.18 ha	No	No (exempt)
Self-build plot	0.25 ha	No	Yes (10%)
Temporary permission (≤5 yrs)	Any	Any	No (exempt)
Major development	Any	Any	Yes (10%)

Conclusion

The BNG changes 6 August 2026 small sites exemption represent a meaningful simplification for minor developments, removing mandatory biodiversity net gain requirements for non-major sites of 0.2 ha or less with no priority habitat. At the same time, the removal of the self-build exemption, the new temporary permission category, and the equal-preference rule for off-site gains reshape the compliance landscape for a broad range of projects.

Actionable next steps for developers, planners, and ecologists:

• Check your application submission date. If submitting on or after 6 August 2026, assess whether the 0.2 ha two-condition test applies.
• Use Natural England's Priority Habitat Inventory as a first check, then commission a site survey where semi-natural vegetation or trees are present.
• Do not rely on self-build status as an automatic exemption; apply the area and habitat test instead.
• For non-major sites above 0.2 ha, use the equal-preference rule to weigh on-site versus off-site BNG delivery options.
• Prepare a short exemption statement even for qualifying sites, as local planning authorities may request supporting evidence.
• Where habitat status is uncertain, adopt a conservative approach and seek specialist ecological advice before submission.

Frequently Asked Questions

Q: What is the exact site area threshold for the BNG small sites exemption?
A: The threshold is 0.2 hectares, measured within the red-line boundary of the planning application. Sites at or below 0.2 ha may qualify, provided no on-site priority habitat is present or affected. [3][8]

Q: Does the small sites exemption apply to applications submitted before 6 August 2026?
A: No. The exemption applies only to applications submitted on or after 6 August 2026. Earlier applications are governed by the rules in force at the time of submission. [6][11]

Q: Can a self-build project still be exempt from BNG?
A: Yes, but only through the 0.2 ha small sites test. The dedicated self-build and custom-build exemption was removed on 6 August 2026. A self-build project on a plot of 0.2 ha or less with no priority habitat qualifies for the small sites exemption. [5][12]

Q: What is priority habitat and why does it matter for the exemption?
A: Priority habitats are those listed under Section 41 of the Natural Environment and Rural Communities Act 2006, such as lowland meadow and ancient woodland. If any priority habitat is present on site or would be adversely affected, the small sites exemption does not apply, regardless of site size. [3][5]

Q: Is the 10% BNG target changing?
A: No. The 10% biodiversity net gain requirement remains unchanged for all non-exempt developments. The August 2026 changes affect who must comply, not the level of gain required. [3][8]

Q: What is the new equal-preference rule for non-major schemes?
A: For non-major developments that must comply with BNG, on-site and registered off-site gains are now treated with equal preference. Developers no longer need to demonstrate that on-site delivery is impractical before using off-site units. [8]

Q: Do exempt sites still need an ecological survey?
A: Not as a mandatory BNG requirement, but local planning authorities may request a short ecological statement to confirm exemption eligibility. Protected species legislation and NPPF ecological requirements apply regardless of BNG exemption status. [1][2][9]

References

[1] Simpler BNG For Small Sites What The August Changes Mean – gfwllp.co.uk

[2] BNG Small Site Exemption August 2026 What Developers Must Do Now – Bng small site exemption august 2026 what developers must do now

[3] Biodiversity Net Gain Exempt Developments – gov.uk

[4] Biodiversity Net Gain Changes 6 August 2026 Small Sites Exemption And New Rules For Developers – Biodiversity net gain changes 6 august 2026 small sites exemption and new rules for developers

[5] BNG Changes 6 August 2026 Small Site Exemption What Every Developer And Planner Must Know Now – Bng changes 6 august 2026 small site exemption what every developer and planner must know now

[6] Biodiversity Net Gain Whats Changing And What It Means For You – defraenvironment.blog.gov.uk

[7] Biodiversity Net Gain Changes 6 August 2026 Developers New Exemptions Explained – Biodiversity net gain changes 6 august 2026 developers new exemptions explained

[8] Understanding Biodiversity Net Gain – gov.uk

[9] Biodiversity Net Gain Small Site 0.2 Hectare Exemption August 2026 Developer Guide – Biodiversity net gain small site 0 2 hectare exemption august 2026 developer guide

[10] Biodiversity Net Gain Changes 6 August 2026 Developers Guide To The New Rules – Biodiversity net gain changes 6 august 2026 developers guide to the new rules

Interactive BNG Exemption Checker:

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‘;
return;
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‘;
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‘;
} else if (area > 0.2 && habitat === ‘no’) {
el.className = ‘cg-result cg-required’;
el.innerHTML = ‘BNG Required, Site area exceeds 0.2 ha. Full 10% biodiversity net gain compliance is required.

‘;
} else {
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el.innerHTML = ‘BNG Required, Priority habitat is present or affected. The small sites exemption does not apply regardless of site area. Full 10% net gain compliance is required.

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