Ten weeks is not long. But it is long enough for a flawed exemption to expose its cracks. The biodiversity net gain small sites exemption October 2026 regime has now been live since 6 August, and planning officers, ecologists and developers are discovering that "exempt" rarely means "exempt from thinking about biodiversity at all."
This matters because the exemption was sold as a simplification. In practice, it has created a narrow gateway that most small-site applicants cannot actually walk through, a Section 73 trap catching anyone trying to vary an older permission, and a regulatory watchdog that publicly rubbished the evidence behind the whole thing.
Key Takeaways
- The biodiversity net gain small sites exemption October 2026 regulations apply only to applications made on or after 6 August 2026, not to Section 73 variations of earlier permissions.
- Sites up to 0.2 hectares with no priority habitat affected may qualify, but developers must still submit a biodiversity exemption statement.
- The Regulatory Policy Committee gave the exemption's impact assessment its lowest possible rating, questioning whether it is justified at all.
- Self-build and custom-build exemptions have been removed; onsite enhancement now sits on equal footing with offsite registered gains in the minor development hierarchy.
- Further exemptions (Environmental Delivery Plans, parks and playing fields) and a brownfield exemption are still under consultation, not yet in force.
What the Small-Sites Exemption Actually Covers
The Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026 took effect on 6 August 2026. They introduced a de minimis exemption for sites up to 0.2 hectares, provided no priority habitat is affected [1][2]. A separate temporary development exemption applies where land is cleared and reinstated within five years, again with no priority habitat involved [2].
Crucially, the biodiversity net gain small sites exemption October 2026 framework is not retrospective. It applies only to planning applications submitted after 6 August 2026 [3][4]. Anything decided before that date, and anything varied afterwards through Section 73, sits outside the new relief.
The self-build and custom-build exemption, which previously gave individual plot-builders a pass, has been removed entirely [3]. That is a meaningful tightening, not a loosening, and it has surprised some smaller developers who assumed the new rules would be universally more lenient.
The Section 73 Trap: Where "Exempt" Stops Applying
This is the detail catching out conveyancers and planning consultants ten weeks in. A Section 73 application, used to vary conditions on an existing permission, does not benefit from the small-sites exemption, even if the underlying site is under 0.2 hectares [3].
Local Government Lawyer and CIEEM have both flagged this as a practical minefield. Developers who secured permission before August 2026 and now want a minor condition change face a stark choice:
- Accept that the Section 73 application may trigger full BNG obligations, including a 10% net gain calculation, even though a brand-new application for the same site might have been exempt.
- Delay the variation, or in some cases withdraw and resubmit as a fresh application, purely to access the exemption, though this carries its own planning risk and cost.
"Essentially the Government has failed to make a persuasive case for weakening the legislation.", Sally Hayns, CIEEM CEO [3]
This quote, made in response to the RPC's criticism, captures the mood among ecologists watching the rollout.
RPC Criticism: A Policy Without a Persuasive Case
The Regulatory Policy Committee reviewed DEFRA's impact assessment for the 0.2-hectare exemption and rated it as not fit for purpose, its lowest classification [4]. The RPC's objections were specific:
| Criticism | Detail |
|---|---|
| No justification for intervention | Assessment failed to demonstrate the exemption was actually needed |
| No review of original policy | Did not reassess whether the original 10% BNG mandate was working as intended |
| Weak SME analysis | Limited evidence on how small and medium developers would be affected |
| Weak monitoring plan | No clear mechanism to track outcomes after implementation |
CIEEM has separately raised concern about the de minimis self-assessment process, which relies on applicants declaring their own site size and habitat status with no independent verification [3]. In effect, developers mark their own homework on whether they qualify for the exemption at all.
What Non-Exempt Small-Site Developers Still Have to Deliver
For the majority of small sites that do not meet the narrow 0.2-hectare, no-priority-habitat test, nothing has changed. Developers must still:
- Commission a baseline habitat survey using UKHab methodology [1][5].
- Run the statutory biodiversity metric to calculate pre- and post-development biodiversity units [1][5].
- Demonstrate a minimum 10% net gain, through onsite habitat creation, offsite registered units, or statutory biodiversity credits [5].
- Submit a biodiversity gain plan for approval before works commence [1].
Even genuinely exempt sites are not paperwork-free. Applicants must submit a biodiversity exemption statement confirming eligibility, which local planning authorities can and do scrutinise [2][6]. Several councils, including Bristol, Richmond and Westminster, have published local guidance clarifying how they expect exemption statements to be evidenced [7][8][9].
How Local Authorities Are Operationalising the Rules
Ten weeks on, implementation is uneven. Some authorities, such as Cornwall, have integrated the exemption criteria directly into validation checklists, rejecting incomplete exemption statements at the point of submission [10]. Others are still relying on case officers to flag exemption claims manually, creating inconsistency in how rigorously the 0.2-hectare and priority-habitat tests are checked.
The minor development hierarchy change is also bedding in slowly. Onsite enhancement now has equal standing with registered offsite gains for minor developments [3], which planning officers say is prompting more applicants to propose modest onsite habitat features, hedgerows, wildflower strips, bat boxes, rather than purchasing offsite units, partly to simplify the application.
What Is Still Coming, Not Yet in Force
It is worth being clear about what has not happened yet, because confusion here is common:
- Exemptions for biodiversity-conservation development within Environmental Delivery Plans are still in development, not yet live.
- Proposed exemptions for parks, playing fields and public gardens remain under consideration.
- Changes to the statutory biodiversity metric itself have not been finalised.
- A brownfield exemption, consulted on in June 2026, remains under review. The Green Gap report warned this exemption would disproportionately affect disadvantaged communities, and DEFRA has not confirmed a direction.
None of these should be assumed to apply to a current application. Treating a proposed exemption as live is one of the most common errors developers' agents are currently making.
Looking Ahead: Budget Week and Beyond
With planning policy frequently resurfacing in fiscal statements, industry watchers are asking whether the 28 October Budget week will bring further BNG announcements. At the time of writing, no confirmed changes have been tabled, and any commentary on this should be treated as expectation rather than settled policy. Given the RPC's criticism and continuing consultations on brownfield and EDP exemptions, further amendment is plausible within the next twelve months, but developers should plan against current regulations, not anticipated ones.
FAQ
Does the small sites exemption apply to Section 73 applications?
No. The biodiversity net gain small sites exemption October 2026 rules apply only to new planning applications made after 6 August 2026, not to Section 73 variations of existing permissions [3].
What size site qualifies for the exemption?
Sites up to 0.2 hectares, provided no priority habitat is affected [2].
Is the self-build exemption still available?
No, it was removed as part of the August 2026 regulations [3].
Do exempt sites need any paperwork?
Yes. Applicants must still submit a biodiversity exemption statement confirming eligibility [2][6].
What did the RPC say about the exemption?
It rated DEFRA's impact assessment as failing to justify the intervention, citing weak SME analysis and a weak monitoring plan [4].
Are brownfield sites exempt yet?
No. A brownfield exemption was consulted on in June 2026 but remains under consideration [3].
Conclusion
Ten weeks of real-world operation have shown that the biodiversity net gain small sites exemption October 2026 framework is narrower, and more procedurally demanding, than its headline suggests. Developers should check application dates against the 6 August 2026 cut-off, assume Section 73 variations fall outside the exemption, and prepare full baseline surveys and metric calculations unless the 0.2-hectare and no-priority-habitat tests are clearly met and documented. Given the RPC's criticism and pending consultations, treat this as an evolving area and seek up-to-date ecological and planning advice before relying on any exemption claim.
References
- Understanding Biodiversity Net Gain. gov.uk.
- Biodiversity Net Gain Exempt Developments. gov.uk.
- New Bng Exemptions Come Into Force Amid Mounting Criticism of Evidence Base. cieem.net.
- Rpc Opinion Impact of Biodiversity Gain Regulations in England 2. gov.uk.
- Biodiversity Net Gain. gov.uk.
- Biodiversity Net Gain Small Developments Guide March 2024 1. gloucester.gov.uk.
- Biodiversity Net Gain for Major Development and Small Site Planning Applications. bristol.gov.uk.
- Biodiversity Net Gain. richmond.gov.uk.
- Biodiversity Net Gain Requirements. westminster.gov.uk.
- Biodiversity Net Gain Bng. cornwall.gov.uk.