On 6 August 2026 the rules on who has to do Biodiversity Net Gain changed materially. Small sites came out of scope, self-build came in, and the on-site-first hierarchy stopped applying to minor development. Here is what the exemption actually says and how to work out whether it covers your site.
What changed on 6 August 2026
Mandatory Biodiversity Net Gain applied to minor development from 2 April 2024. For a little over two years, a two-plot infill scheme on a scrap of garden land was subject to the same 10% biodiversity gain condition as a 400-home allocation, differing only in which metric you were allowed to use to prove it.
That stopped on 6 August 2026. Defra published the amending regulations on 13 July 2026 and confirmed the changes on its environment blog, introducing an area-based exemption that takes a very large share of development out of the regime entirely. Planning Portal data reported by The Planner suggested that 13,601 of the 31,546 applications subject to BNG up to that point — around 43% — would have fallen outside it.
If you have been applying BNG by reflex since 2024, the first question on every new small site is now whether the regime applies at all.
The 0.2 hectare exemption
The GOV.UK biodiversity net gain guidance states the test in two parts. Development is exempt where:
- the site has an area no larger than 0.2 hectares, and
- the development does not impact an onsite priority habitat.
Both limbs have to hold. Neither is quite as simple as it reads.
0.2 hectares is 2,000 square metres, and it is measured by the area inside the red line boundary, hardstanding included. This matters more than it sounds. It is a site area test, not a test of how much habitat you are losing. A 1,900 m² yard that is entirely concrete, with no habitat of any biodiversity value on it at all, is exempt because of its size. A 2,100 m² site that is also entirely concrete is in scope, and has to go through the metric to demonstrate a 10% gain on a baseline of approximately zero.
Draw the red line before you draw anything else. Because the threshold is absolute and the consequence is binary, the position of the red line is now a live design decision on any site near 0.2 hectares. A site at 0.21 hectares that could sensibly be reduced is worth examining — not as a device, but because an application boundary drawn loosely around a smaller development is the most common way to land in scope unnecessarily.
The priority habitat carve-out
The second limb is where small sites still get caught, and it is widely misread.
The exemption falls away where the development negatively impacts onsite priority habitat. Priority habitat means habitat of principal importance listed under section 41 of the Natural Environment and Rural Communities Act 2006.
Two practical consequences:
- Presence alone does not defeat the exemption. The question is impact, not existence. A priority habitat in a corner of the site that the development genuinely does not touch, disturb or shade does not pull a 0.15 hectare scheme back into scope. Demonstrating that convincingly is a different matter, and on a constrained small site it is often easier to accept that you are in scope than to argue no impact.
- Most hedgerows are priority habitat. This is the trap. Hedgerows are the single most common priority habitat on small development sites, and removing or breaching a length of hedge to form an access is one of the most common things a small development does. A 0.1 hectare plot with a new vehicle crossover through a hedge is very likely still in scope despite being well under the threshold.
The full list of current exemptions
The 0.2 hectare rule sits alongside several others. As the GOV.UK guidance has it, development is currently exempt where it is:
| Exemption | Test |
|---|---|
| Householder development | As defined in Article 2(1) of the Town and Country Planning (Development Management Procedure) (England) Order 2015 |
| Small sites | Site no larger than 0.2 ha, no impact on onsite priority habitat — applications made on or after 6 August 2026 |
| De minimis | Less than 25 m² of onsite habitat with biodiversity value above zero, and less than 5 m of onsite linear habitat such as hedgerow, and no impact on onsite priority habitat |
| Temporary development | Permission for 5 years or less, whole development temporary, no impact on onsite priority habitat — applications made on or after 6 August 2026 |
| Development orders | Permission granted by a development order under section 59, including permitted development rights |
| Urgent Crown development | Granted under section 293A of the Town and Country Planning Act 1990 |
| Biodiversity gain sites | Development undertaken solely or mainly to fulfil the gain condition for another development |
| High speed railway | Development forming part of, or ancillary to, the HS2 network under section 1(2) of the High Speed Rail (Preparation) Act 2013 |
For a non-householder site of 0.2 hectares or less, the guidance directs you to the 0.2 hectare exemption rather than the de minimis one. De minimis still earns its place on larger sites with almost no habitat on them.
Three other things changed at the same time
Self-build lost its exemption. Self-build and custom build housing — up to 9 dwellings on a site no larger than 0.5 hectares — was exempt for applications made before 6 August 2026. That exemption was withdrawn as part of the same package, on the reasoning that the new area-based exemption covers most of the same ground. A self-build scheme can still rely on the 0.2 hectare exemption if it qualifies on area, but a 0.4 hectare self-build plot that was exempt in July 2026 is in scope in October 2026.
On-site-first now applies only to major development. Previously every scheme had to work down the hierarchy: on-site gains first, off-site second, statutory credits last. From 6 August, that sequencing requirement binds only major development. Minor development that is still in scope can go straight to off-site provision without first demonstrating that on-site options were exhausted. For a tight urban site where on-site gain was always going to be a token green roof, this is a genuine simplification.
Temporary development came out of scope. Where the whole development is temporary and the land is to be reinstated within 5 years or less, it is exempt, subject to the same priority habitat carve-out. Combined periods across earlier permissions for the same development cannot exceed 5 years, so this is not a mechanism for rolling consents.
Transitional rules: the date that matters is submission
The new exemptions apply only where the application for planning permission was made on or after 6 August 2026. Applications already in the system continue under the rules they entered under.
This produces an awkward but predictable result through late 2026: two near-identical small sites, one submitted in July and one in September, on different sides of the line. If you have an application submitted before 6 August that is now stuck part-way through discharging a biodiversity gain condition, the exemption does not retrospectively rescue it. The regulations also deal with variations of existing permissions, and that is worth specific advice rather than assumption if you are varying a pre-August consent.
What is still coming
The August package was explicitly an instalment, not a conclusion:
- Brownfield. A consultation on a targeted exemption for certain residential brownfield development closed on 10 June 2026. The government has said it will respond in due course. Figures of up to 2.5 hectares have circulated in commentary; nothing is confirmed.
- NSIPs. Mandatory BNG is expected to extend to Nationally Significant Infrastructure Projects from 2 November 2026, a date that also appears in GOV.UK's statutory credit price guidance. Confirm it against the live guidance before relying on it.
- Announced but undated. Exemptions for development whose primary objective is to conserve or enhance biodiversity, and a targeted exemption for enhancing parks, playing fields and public gardens. Changes to the statutory biodiversity metric itself were also flagged, with no date.
Treat scope as a date-stamped question. Four separate things about BNG scope changed or were announced in 2026 alone. The useful habit is to record, for each application, the date it was submitted and the exemption position as at that date — because by the time a condition is discharged, the guidance will have moved again.
How to work out whether you are in scope
In order, for a site under consideration today:
- Is it householder development, or permitted development? If yes, out of scope, and the rest of this does not apply.
- Measure the red line area, including hardstanding. Over 0.2 hectares, keep going. At or under, move to step 3.
- Identify onsite priority habitat. Hedgerows first, then anything on the section 41 list. If there is none, you are exempt.
- If there is priority habitat, ask whether the development impacts it. Access through a hedge, root protection areas, lighting, drainage outfalls, construction compound footprint. Impact brings you back in scope.
- If you are in scope, decide which metric applies — the statutory biodiversity metric or the simpler Small Sites Metric, which has its own separate eligibility conditions.
- Record the submission date against that assessment, because it determines which version of the rules governs the application.
Common mistakes
- Assuming the exemption is about habitat. It is a site area test. Concrete counts towards 0.2 hectares.
- Forgetting the hedge. The most common priority habitat on small sites, and the most commonly removed feature. Many sites comfortably under 0.2 hectares remain in scope for this reason alone.
- Applying the exemption to a pre-August application. The submission date governs, not today's date.
- Assuming self-build is still exempt. It is not, for anything submitted on or after 6 August 2026.
- Still working on-site-first on a minor scheme. Permitted, but no longer required — and on constrained sites it can cost design quality for no compliance benefit.
- Treating a 2024-vintage BNG note as current. Anything written before July 2026 describes a regime that no longer applies to new small-site applications.
How this connects to your wider environmental reporting
The 0.2 hectare exemption removes a reporting burden; it does not remove the underlying planning requirement to understand what is on a site. Ecology surveys, protected species licences and the habitats considerations that sit behind Biodiversity Net Gain are unaffected by it, and the priority habitat question still has to be answered properly in order to claim the exemption at all.
Where BNG does still apply, the evidence problem is the same one that runs through carbon reduction plans and environmental management plans: a position calculated once at design stage and never revisited is the position most likely to be challenged. VerdCore's BNG reporting software keeps the biodiversity assessment next to the site data it has to stay consistent with.