The Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026 came into force on 6 August 2026. They apply to planning applications made on or after that date, and they are the first tranche of the reforms Defra confirmed in its consultation response of 15 April 2026.
The four changes that matter
1. A new small-site exemption at 0.2 hectares
Development where the site area within the red-line boundary is 0.2 hectares (2,000 m²) or less is exempt from mandatory biodiversity net gain. Two things are routinely misread here. First, the threshold applies to the whole application site within the red line — not the development footprint, not the area of habitat affected. Second, it is disapplied where the development negatively affects on-site priority habitat.
2. Temporary permissions of five years or less
Where the whole development is temporary and permission is granted for five years or less, BNG does not apply — again subject to the priority-habitat condition. This matters for construction compounds, meanwhile use, and some energy and minerals arrangements.
3. The self-build and custom-build exemption is gone
Withdrawn on the same date, on the reasoning that most self-build schemes will now fall within the new 0.2 hectare exemption anyway. Most will. Some will not — a self-build plot on a generous rural site can comfortably exceed 2,000 m², and those schemes have moved from exempt to in scope.
4. On-site first now binds only major development
Previously an applicant had to demonstrate that on-site enhancement opportunities had been maximised before relying on off-site units. From 6 August that requirement applies only to major development. For minor schemes, off-site units can be used without first evidencing that on-site delivery was not achievable. On constrained urban sites where on-site habitat creation fights density and design, that is a material easing.
The priority-habitat condition is the whole story
Both new exemptions, and the existing de minimis exemption, fall away where on-site priority habitat is negatively affected. Priority habitats are those listed as being of principal importance under section 41 of the Natural Environment and Rural Communities Act 2006.
So the question a developer now has to answer is not "is my site under 0.2 hectares?" — that part is easy. It is "can I demonstrate there is no priority habitat within my red line that my scheme would negatively affect?" That is an ecological judgement, and a planning officer is entitled to ask for it to be evidenced before validating an application on an exempt basis.
A small site is not automatically an ecologically uninteresting site. Some of the highest-distinctiveness habitat we see sits in half-acre parcels: unimproved neutral grassland behind a farm building, a strip of lowland heath on a road verge, a pond with a marginal fringe.
The practical answer is proportionate. Natural England's Priority Habitat Inventory gives a first indication, and your local environmental records centre holds local data. But the inventory is a mapping product, not a survey, and it is wrong at parcel scale often enough that we would not rest a validation argument on it alone. A desk study plus a short walkover by an ecologist, at the right time of year, settles it — and costs a fraction of a full metric assessment.
What has not changed
- The 10% minimum gain, the 30-year maintenance obligation and the biodiversity gain plan condition all remain for schemes in scope.
- Applications made before 6 August 2026 are unaffected; the new exemptions apply to applications made on or after that date.
- Permissions already granted subject to the biodiversity gain condition still need a biodiversity gain plan approved before commencement.
- Ecology has not gone away. Protected species law, the nesting bird season, designated site obligations and the NPPF all operate independently of BNG. A site exempt from net gain can still need a bat survey, a great crested newt licence, and a refusal if significant harm cannot be avoided.
Still moving
Defra has confirmed further secondary legislation later in 2026 to exempt development whose primary objective is to conserve or enhance biodiversity, and targeted development enhancing parks, playing fields and public gardens. A separate consultation on a possible exemption for brownfield residential development on sites up to 2.5 hectares closed on 10 June 2026 and the response is awaited. Updates to the statutory biodiversity metric and its user guides are expected later in the year, with transitional arrangements for projects already using the current version, and a longer-term move from the Excel tools to a digital service.
What to do about it
- Check your red line against 0.2 hectares early. If you are near the threshold, small boundary changes may decide whether BNG applies at all.
- Evidence the priority-habitat position before you rely on an exemption. A desk study and walkover is the proportionate step, and it is better done now than in response to a validation query.
- Do not read "BNG exempt" as "ecology clear". The protected species and designated site obligations are untouched, and they are the ones that carry criminal liability.
Written by the Virtus Green technical team. This is a summary of our reading of current guidance and regulation as at 12 August 2026; it is not legal advice, and positions change. Confirm current requirements with your local planning authority before you rely on anything here.