On 15 April 2026, Defra confirmed a package of new exemptions:
- 0.2 hectare area-based exemption. All development on a site of 0.2 hectares or less is fully exempt from BNG. Defra estimates this removes BNG from around half of residential planning permissions previously in scope. The exemption does not apply where priority habitats are affected.
- Removal of the self-build / custom-build exemption. Most of these projects will fall under the new 0.2ha exemption instead.
- Biodiversity-led developments. Schemes whose primary objective is to conserve or enhance biodiversity are exempt.
- Temporary planning permissions granted for up to 5 years are exempt, unless on-site priority habitats are affected.
- Parks, playing fields and public gardens. Developments enhancing these spaces are exempt.
- Equal-status off-site delivery for minor developments. For residential schemes with 9 or fewer dwellings on a site of 1 hectare or less, off-site delivery has equal status with on-site delivery — loosening the existing biodiversity gain hierarchy.
Secondary legislation introducing these measures is expected before 31 July 2026.
A separate consultation on a targeted brownfield residential exemption is open until 10 June 2026 — see the 2026 reforms page for detail.
Current exemptions (as of early 2026)
Most developments in England that require planning permission under the Town and Country Planning Act 1990 must deliver 10% biodiversity net gain. However, the following are currently exempt:
| Exemption | Detail | Status |
|---|---|---|
| De minimis threshold | Developments impacting less than 25 square metres of habitat (or less than 5 metres of linear habitat) | Current law — changing before 31 July 2026 |
| Householder applications | Extensions, loft conversions, outbuildings, and other works to existing homes under householder permitted development | Current law |
| Biodiversity gain sites | Development that is itself creating habitat for BNG purposes (i.e., building a habitat bank) | Current law |
| Self-build & custom housebuilding | Certain self-build and custom housebuilding developments (subject to conditions) | Current law — exemption being removed (most projects will fall under the new 0.2ha threshold) |
| Permitted development | Works carried out under permitted development rights that do not require planning permission | Current law |
| Pre-BNG permissions | Planning permissions granted before 12 Feb 2024 (major) or 2 April 2024 (small sites), and variations to those permissions | Transitional |
| High Speed 2 | Development authorised by the High Speed Rail Act | Current law |
What's changing in 2026
The government has announced several reforms to the BNG exemption framework, designed to reduce administrative burden on smaller developments while maintaining environmental protection for larger ones.
The 0.2 hectare exemption explained
The new 0.2 hectare (2,000 sqm) area-based exemption is the most significant change to BNG since its introduction. Here's what we know:
What it means
Developments on sites of less than 0.2 hectares will no longer need to demonstrate 10% biodiversity net gain. For context, 0.2 hectares is roughly equivalent to half an acre, or about 8 average-sized detached house plots.
Why it matters
The current 25 sqm threshold is so low that almost every development — including single homes, small extensions with any garden impact, and minor commercial projects — triggers BNG requirements. This has created a disproportionate administrative burden on small developers, many of whom have found BNG compliance costs and complexity difficult to manage.
The 0.2 hectare threshold will exempt a large number of small and medium residential developments, urban infill projects, and small commercial schemes from BNG entirely.
What we don't yet know
- Transitional arrangements: How will the new threshold apply to sites already in the planning system? If you've submitted a planning application with BNG information, will you need to maintain it?
- Measurement methodology: Is it the total site area or the area of habitat impacted? This distinction matters significantly.
- Impact on the off-site market: Fewer developments needing off-site units could affect demand in some areas, though NSIP and larger development demand may compensate.
The brownfield consultation
Alongside the 0.2 hectare exemption, the government has indicated a rapid consultation on a targeted BNG exemption for residential brownfield development. Early suggestions include:
- Exemption for residential developments on brownfield sites up to 2.5 hectares
- Potential revisiting of the open mosaic habitat definition — a brownfield habitat type that has caused significant confusion and cost for developers
- Possible relaxing of trading rules relating to open mosaic habitats
Open mosaic habitats on previously developed land can score as Medium distinctiveness in the metric, meaning developers must offset losses with Medium or higher habitat — even when the site appears to be derelict wasteland. This has been one of the most contentious aspects of BNG implementation and a major cost driver for brownfield development.
Spatial risk multiplier — moving from LPAs to LNRS areas
The spatial risk multiplier — the metric penalty applied when off-site biodiversity units come from outside the development's local area — will be reassessed against Local Nature Recovery Strategy (LNRS) areas instead of LPA and NCA boundaries.
With only 48 LNRS areas across England — compared with 337 LPAs — this materially expands the geographic pool of off-site units that can be used without attracting a multiplier penalty. For developers sourcing units, the practical effect is that units from a wider area can now count at face value rather than at a higher cost. For habitat bank operators and landowners, units registered in their LNRS area can serve a much larger catchment of potential buyers.
Simplified routes for small developments
Even where BNG applies, the government is also introducing simplified compliance routes for developments that sit above the exemption threshold but below major development thresholds:
- Streamlined offsite BNG delivery mechanisms
- The existing Small Sites Metric — a simplified version of the full statutory metric designed for small development sites
- The sub-0.25 unit shortcut: if your development needs less than 0.25 biodiversity units to achieve 10% BNG, and the entire site is covered by buildings or private gardens, you can go directly to statutory credits without needing to evidence that you approached off-site suppliers
Not sure if you're exempt?
Our free Exemption Checker walks you through the criteria in under a minute. Answer a few questions about your development and get a clear answer.
What to do if you're not exempt
If your development is not exempt from BNG, don't panic. The process is manageable when approached early and systematically:
- Engage an ecologist to conduct a baseline habitat survey as early as possible in the design process
- Run the metric to understand your baseline value and the 10% uplift target
- Optimise your site design to maximise on-site habitat creation and retention
- Check off-site availability in your area using our Postcode Lookup tool
- Budget for BNG costs early — include potential off-site unit purchases or credit costs in your financial appraisal
- Prepare your Biodiversity Gain Plan for LPA submission — this is a pre-commencement condition
For a full step-by-step guide, read our Developer Compliance Guide.