BNG Reforms Two Weeks In: What the 6 August 2026 Changes Mean for UK Planning Applications Now

Last updated: August 20, 2026

Quick Answer: SI 2026 No. 790 (the Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026) came into force on 6 August 2026, introducing four significant changes: a 0.2 ha small-site exemption, a five-year temporary-development exemption, removal of the self/custom-build exemption, and a relaxed off-site hierarchy for minor developments. These changes apply only to planning applications submitted on or after 6 August 2026. Applications validated before that date continue under the previous rules.

Key Takeaways

• The 0.2 ha (2,000 m²) small-site exemption removes BNG obligations from many one- and two-dwelling schemes, provided no priority habitat is affected.
• Self-build and custom-build projects submitted from 6 August 2026 onwards must now comply with the 10% BNG requirement unless they qualify under a different exemption.
• Temporary developments permitted for five years or less, with full land restoration, are now exempt from mandatory BNG.
• For minor developments still subject to BNG, off-site gains now sit on equal footing with on-site creation in the biodiversity gain hierarchy.
• Statutory credits remain the last resort and carry steep costs: from approximately £42,000 for some habitat types up to around £650,000 per unit for saltmarsh.
• Private biodiversity units typically cost £20,000,£35,000 for medium-distinctiveness habitats and £40,000,£90,000-plus for high-distinctiveness habitats.
• All four reforms are prospective only: pre-6 August applications are unaffected.
• Developers should not manipulate red-line boundaries to fall below the 0.2 ha threshold purely to avoid BNG.
• Local planning authorities (LPAs) are already updating validation checklists to reflect the new thresholds.
• Mandatory BNG for Nationally Significant Infrastructure Projects (NSIPs) is expected from November 2026, which may increase statutory credit demand again.

What Is Biodiversity Net Gain and How Does It Work in UK Planning?

Biodiversity net gain (BNG) is a legal requirement under Schedule 7A of the Town and Country Planning Act 1990 (inserted by the Environment Act 2021) that obliges most developers to leave biodiversity in a measurably better state than before development. In practice, this means demonstrating a minimum 10% net gain in biodiversity units, calculated using Natural England's statutory Biodiversity Metric.

Developers use a before-and-after habitat assessment to calculate the biodiversity unit value of a site. If on-site measures cannot deliver the full 10% uplift, developers must purchase off-site biodiversity units from registered habitat banks or, as a last resort, buy statutory credits from the government. For a thorough grounding in the process, see this biodiversity net gain explained guide and Natural England's own understanding biodiversity net gain guidance [7].

BNG has been mandatory for major developments since February 2024 and for small sites since April 2024. The 6 August 2026 reforms refine, rather than replace, that framework [2].

What Changed on 6 August 2026: The Four BNG Reforms Explained

As of 20 August 2026, the four reforms introduced by SI 2026 No. 790 have been in force for exactly two weeks. A 21 July 2026 letter from DEFRA to chief planning officers signalled the policy aim as making BNG "more proportionate" for the smallest sites without weakening the overall 10% requirement [6].

The four changes are:

1. New 0.2 ha small-site exemption – sites no larger than 0.2 ha with no impact on priority habitat are exempt from BNG.
2. Five-year temporary-development exemption – wholly temporary schemes permitted for five years or less, with land restoration, are exempt.
3. Removal of the self/custom-build exemption – self-builders submitting from 6 August 2026 must now meet BNG requirements.
4. Relaxed minor-development hierarchy – off-site gains now sit alongside on-site creation rather than below it for minor developments [3][5][8].

All four changes are prospective only. Applications validated before 6 August 2026 continue under the previous BNG rules, and transitional protections apply to variations of previously exempt permissions [4][5].

Is My Small Development Exempt from the New BNG Rules?

A site qualifies for the new small-site exemption if the red-line planning application area is no larger than 0.2 ha (2,000 m²) and the development does not impact any on-site priority habitat. Both conditions must be met simultaneously [4].

What this means in practice:

• A single dwelling on a 0.15 ha infill plot with no priority habitat: likely exempt.
• A two-dwelling scheme on a 0.19 ha brownfield site with a small area of marshy grassland (a priority habitat): not exempt, because priority habitat is present.
• A 0.22 ha scheme: not exempt regardless of habitat, because it exceeds the threshold.

Common mistake: Some developers are reportedly considering drawing red-line boundaries tightly to bring sites under 0.2 ha. DEFRA guidance and LPA validation teams are alert to this. Artificially constrained red lines that exclude land clearly associated with the development are likely to be challenged [5][9].

For further detail on how exemptions work across different project types, the exempt projects guidance provides a useful reference. The GOV.UK biodiversity net gain exempt developments page confirms the precise qualifying criteria [4].

What the Removal of the Self-Build Exemption Means for Applications in Progress

Self-build and custom-build schemes submitted on or after 6 August 2026 must comply with the 10% BNG requirement. The previous exemption has been removed by SI 2026 No. 790 [4][8].

Who is protected by transitional provisions:

• Applications validated before 6 August 2026 under the old exemption retain that exemption.
• Variations (Section 73 applications) of permissions that were previously exempt as self-build may also retain transitional protection, but this should be confirmed with the LPA on a case-by-case basis [5][12].

Action steps for self-builders currently in planning:

1. Confirm with the LPA whether your application was validated before or after 6 August 2026.
2. If validated after 6 August, commission a baseline habitat survey immediately if one has not been done.
3. Check whether the site qualifies under the 0.2 ha exemption instead.
4. If BNG is required, engage an ecologist to run the Biodiversity Metric and identify whether on-site habitat creation (e.g., native planting, hedgerows, wildflower areas) can deliver the 10% uplift.
5. If on-site delivery falls short, budget for off-site unit purchases early. See the section on costs below.

The BNG for small development projects guide sets out practical options for smaller schemes navigating these requirements.

How Does the Five-Year Temporary-Development Exemption Work?

Temporary developments are now exempt from mandatory BNG where all four of the following apply: the entire development is temporary in nature; planning permission is granted for five years or less; the land is to be restored to its previous condition; and the scheme does not negatively affect priority habitat [4][6].

This exemption is relevant for construction compounds, temporary car parks, short-term event infrastructure, and similar uses. It does not apply to developments that are temporary in name but result in lasting habitat loss. LPAs will scrutinise whether the restoration condition is genuinely enforceable [8].

How the Relaxed Minor-Development Hierarchy Affects Off-Site BNG Options

For minor developments that remain subject to BNG, the biodiversity gain hierarchy has been modified so that off-site biodiversity gains are now on equal footing with on-site habitat creation. Previously, developers had to demonstrate they had exhausted on-site options before turning to off-site units [3][6].

This is a meaningful practical change. Minor residential schemes (typically one to nine dwellings) often sit on constrained plots where meaningful on-site habitat creation is difficult. The revised hierarchy gives these developers the freedom to go straight to off-site units without having to justify why on-site delivery is impractical.

Important caveat: Statutory credits remain at the bottom of the hierarchy for all development types, including minor developments. They should not be used as a first resort [3][11]. For a detailed comparison of off-site delivery routes, see BNG off-site land banking vs habitat banking and biodiversity net gain off-site or on-site delivery.

How Much Will BNG Compliance Cost for Residential Developments?

BNG compliance costs vary significantly depending on the delivery route chosen. As of August 2026, the cost gap between statutory credits and private biodiversity units remains wide.

Statutory credit costs (government-set, last updated by Natural England):

Habitat Type	Approximate Cost per Unit
Lower-distinctiveness grassland	~£42,000
Medium-distinctiveness grassland	~£100,000,£200,000
Woodland	~£250,000,£350,000
Saltmarsh	~£650,000

Private biodiversity unit costs (market estimate, August 2026):

• Medium-distinctiveness habitats: approximately £20,000,£35,000 per unit
• High-distinctiveness habitats: approximately £40,000,£90,000-plus per unit

The cost difference between statutory credits and private units can be substantial, particularly for high-distinctiveness habitats. A developer needing saltmarsh credits who relies on statutory credits rather than sourcing private units from a habitat bank could face costs several times higher [9][10].

For a full breakdown of how these figures are structured, the cost of biodiversity units and statutory credits guide is a practical starting point. Developers who want to purchase private units should also review the buy biodiversity units options available through registered habitat banks.

How Do the New BNG Rules Affect My Planning Application Timeline?

The reforms affect timeline in two main ways. First, LPAs are updating validation checklists to reflect the new exemption thresholds, which means some applications that previously required a Biodiversity Metric calculation may now be validated without one. Second, self-build schemes that were previously exempt now need ecological surveys and BNG plans before validation, which adds time to pre-application preparation [9][10].

For applications being determined right now (as of 20 August 2026):

• Applications submitted before 6 August 2026: no change to BNG requirements; proceed under the original rules.
• Applications submitted on or after 6 August 2026: the new exemptions and hierarchy apply immediately.
• If an application straddles the boundary (e.g., pre-application discussions began before 6 August but the formal application was submitted after), the date of validation is the determining factor [5].

Can I Use Off-Site Biodiversity Credits Instead of On-Site Measures?

Yes, and the 6 August 2026 reforms make this easier for minor developments. Under the revised hierarchy for minor development, developers can choose off-site biodiversity units without first having to demonstrate that on-site delivery is impractical [3][6].

For major developments, the original hierarchy still applies: on-site measures first, then off-site units, then statutory credits as a last resort. The relaxation is specific to minor development [11].

When sourcing off-site units, developers should ensure the habitat bank is registered on the Natural England biodiversity gain sites register and that the unit type matches the habitat type lost on-site. Mismatched unit types are a common reason BNG plans are rejected by LPAs [9].

What Are the Common Mistakes Developers Are Making with the New BNG Process?

Two weeks in, several recurring issues are emerging across the industry [9][10]:

• Assuming the 0.2 ha exemption is automatic. The priority habitat test is a separate hurdle. Sites with any priority habitat present do not qualify, regardless of size.
• Misreading the transitional provisions for self-build. Some self-builders with applications in progress are incorrectly assuming they retain the old exemption when their application was in fact validated after 6 August.
• Treating statutory credits as a budgeting shortcut. Statutory credits are priced deliberately high to discourage their use. Developers who budget for statutory credits without first exploring private unit markets are likely to overspend significantly.
• Ignoring the minor-development hierarchy change. Some planning consultants are still applying the old hierarchy to minor schemes, advising clients to justify why on-site delivery is impractical before considering off-site options. This is no longer required.
• Boundary manipulation. Drawing red lines to exclude land in order to fall below 0.2 ha is being flagged by LPAs and may result in invalid applications or enforcement action.

For a broader look at how to structure a compliant BNG plan, the guide to biodiversity net gain for developers covers the full process from baseline survey to submission.

What Happens If I Don't Meet BNG Requirements on My Project?

Failure to satisfy BNG requirements is a material planning consideration and will result in refusal of planning permission for non-exempt applications. BNG is not a condition that can be discharged post-consent as an afterthought; it must be addressed in the application itself through a completed Biodiversity Metric calculation and, where off-site units are required, a registered biodiversity gain plan [7][2].

If a BNG calculation is submitted and the LPA disagrees with the methodology or unit totals, the developer can appeal through the standard planning appeal process. However, the Biodiversity Metric is a statutory tool, so disputes typically centre on baseline habitat classification rather than the metric itself [2][9].

Frequently Asked Questions

Does the 0.2 ha exemption apply to applications already in the planning system before 6 August 2026?
No. The exemption applies only to applications submitted on or after 6 August 2026. Applications validated before that date continue under the previous BNG rules, regardless of site size [4][5].

I submitted a self-build application before 6 August 2026 under the old exemption. Am I still protected?
Yes. Applications validated before 6 August 2026 retain transitional protection and the old self-build exemption still applies to them. Only new applications submitted from 6 August 2026 onwards are affected by the removal [4][8].

Can a minor development scheme go straight to statutory credits under the new hierarchy?
No. Statutory credits remain at the bottom of the biodiversity gain hierarchy for all development types. The relaxation for minor developments allows off-site units to be used without first exhausting on-site options, but statutory credits are still a last resort [3][6].

How is the 0.2 ha threshold measured?
The threshold applies to the red-line planning application boundary, not just the footprint of the proposed building. The entire application site area must be no larger than 0.2 ha (2,000 m²) [4].

Are there any BNG changes coming after August 2026 that developers should plan for?
Mandatory BNG for Nationally Significant Infrastructure Projects is expected to come into force in November 2026. This is likely to increase demand for biodiversity units, particularly for higher-distinctiveness habitats, which may affect private unit pricing [9][11].

What if my site is just over 0.2 ha but has no priority habitat? Am I still required to comply with BNG?
Yes. Both conditions (site area no larger than 0.2 ha and no impact on priority habitat) must be satisfied for the exemption to apply. A site of 0.21 ha with no priority habitat is not exempt because it exceeds the size threshold [4][5].

Conclusion

As of 20 August 2026, the BNG reforms introduced by SI 2026 No. 790 have reshaped the compliance landscape for a significant portion of UK planning applications. The 0.2 ha small-site exemption will reduce the BNG burden on many small residential schemes, but it is not a blanket escape route: the priority habitat test catches sites that might otherwise assume they qualify. The removal of the self-build exemption is the most significant compliance shift for individual applicants, and those with applications currently in the system need to act quickly to commission baseline surveys and BNG plans.

Immediate action steps for developers:

1. Confirm your application's validation date relative to 6 August 2026.
2. If validated after 6 August, check both the 0.2 ha threshold and the priority habitat test before assuming exemption.
3. Self-builders: engage an ecologist now if you have not already done so.
4. For minor developments subject to BNG, explore off-site unit markets before defaulting to statutory credits.
5. Get comparative quotes from private habitat banks alongside the statutory credit schedule to understand the true cost gap.
6. Confirm with your LPA that their validation checklist reflects the updated exemptions.

The 10% BNG requirement itself has not changed. What has changed is who it applies to, how it can be delivered, and at what cost. Getting these details right at the application stage is far less expensive than addressing them after a refusal.

Interactive BNG Cost Estimator

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Estimates only. Statutory credit prices are set by Natural England. Private unit prices reflect August 2026 market range. Always obtain formal quotes.

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References

[1] BNG August 2026 Regulations Confirmed – the-ferals.co.uk

[2] Planning Geek: BNG – planninggeek.co.uk

[3] BNG Changes From 6 August 2026 What You Need To Know – planninggateway.co.uk

[4] Biodiversity Net Gain Exempt Developments (GOV.UK) – gov.uk

[5] Biodiversity Net Gain BNG Changes From 6 August 2026 What You Need To Know – union4.co.uk

[6] DEFRA Letter to CPOs: NSD and BNG (21 July 2026) – assets.publishing.service.gov.uk

[7] Understanding Biodiversity Net Gain (GOV.UK) – gov.uk

[8] CIEEM: New BNG Rules and Exemptions Apply From 6 August 2026 – cieem.net

[9] BNG Changes 6 August 2026: What UK Developers Must Do Now – Bng changes 6 august 2026 what uk developers must do now

[10] Biodiversity Net Gain 6 August 2026 Reforms One Week On – Biodiversity net gain 6 august 2026 reforms one week on early impact for uk developers and ecologists