Exemptions · England · Updated 2026-09-17
BNG exemptions
BNG exemptions in England cover householder applications, permitted development, sites of 0.2 hectares or below and temporary development of 5 years or less (both from 6 August 2026, where no priority habitat is impacted), de minimis impacts under 25 square metres of habitat or 5 metres of hedgerow, biodiversity gain sites, urgent Crown development and the high-speed rail network. Applications made before 12 February 2024 are outside the regime, and the self-build exemption closed to new applications on 6 August 2026.
Current exemptions (cited, not exhaustive legal advice)
| Exemption | Test | In force |
|---|---|---|
| Householder development | Application is a "householder application" under article 2(1) of the Development Management Procedure Order 2015: extensions, conservatories, loft conversions and similar works to a dwelling. | 12 February 2024 |
| Permitted development | Planning permission granted by a development order under section 59 TCPA 1990, including permitted development rights. | 12 February 2024 |
| Sites of 0.2 hectares or below | Site area inside the red line is 0.2 ha or below and the development does not impact on-site priority habitat. | Applications made on or after 6 August 2026 |
| De minimis | No impact on priority habitat, and impact on less than 25 m² of on-site habitat with a biodiversity value above zero and less than 5 m of linear habitat such as hedgerow. | 12 February 2024 (clarified 14 July 2026) |
| Temporary development | Whole development is temporary, permission is for 5 years or less (cumulatively with earlier temporary permissions), and no priority habitat is impacted. | Applications made on or after 6 August 2026 |
| Biodiversity gain sites | Development undertaken solely or mainly to fulfil the biodiversity gain condition of another development. | 12 February 2024 |
| Urgent Crown development | Permission under section 293A TCPA 1990. | 12 February 2024 |
| High-speed rail network | Development forming part of, or ancillary to, the network in section 1(2) of the High Speed Rail (Preparation) Act 2013. | 12 February 2024 |
Transitional arrangements and closed exemptions
- Applications before mandatory BNG. Applications made before 12 February 2024 (any size) and small-development applications made before 2 April 2024 are not subject to BNG.
- Section 73 variations. Where the original permission was outside BNG, a later variation generally remains outside it. Retrospective permissions under section 73A are not subject to BNG.
- Self-build and custom build (closed). Up to 9 self-build dwellings on 0.5 ha or less were exempt only where the application was made before 6 August 2026.
- Other routes to permission (local and neighbourhood development orders, simplified planning zones, deemed permission, enforcement-appeal permission) have not yet been brought into BNG.
- Priority habitat overrides. The 0.2 ha, de minimis and temporary exemptions all fall away if the development decreases the biodiversity value of on-site priority habitat.
What to check before claiming an exemption
- Date of application. The 0.2 ha and temporary exemptions apply only to applications made on or after 6 August 2026; the self-build exemption only before it.
- Priority habitat. Check the Natural England priority habitat inventory and your survey for section 41 habitats inside the red line. If any is impacted, most size-based exemptions do not apply.
- Measure the red line, not the footprint. The 0.2 ha threshold is the whole site area inside the application boundary.
- Evidence de minimis carefully. Provide plans showing habitat parcels and impacts; where cumulative small impacts could exceed 25 m², a completed pre- and post-development metric is strongly encouraged.
- Focus on the simplest applicable exemption. Planning Practice Guidance says applicants and authorities should concentrate on the exemption that is most appropriate and easiest to assess rather than evidencing all of them.
- State it on the form. You must declare the exemption and your reasons on the planning application; the authority checks at validation.
If the development is not exempt, a pre-development metric is needed with the application and a biodiversity gain plan must be approved before commencement: see the bng assessment process. Use the non-statutory estimator to see how much value your site holds before you instruct an ecologist; it flags the 0.2 ha threshold automatically.
Frequently asked questions
What sites are exempt from BNG?
In England, BNG does not apply to householder applications, permitted development, sites of 0.2 hectares or below (applications made on or after 6 August 2026, no priority habitat impacted), temporary development permitted for 5 years or less (same date and test), development impacting under 25 square metres of habitat and under 5 metres of hedgerow (de minimis), biodiversity gain sites, urgent Crown development and the high-speed rail network. Applications made before 12 February 2024, or before 2 April 2024 for small developments, are also outside the regime.
Is self-build exempt from biodiversity net gain?
Not for new applications. The self-build and custom-build exemption (up to 9 dwellings on 0.5 hectares or less) applies only where the planning application was made before 6 August 2026, or to a variation of a permission that was itself exempt. GOV.UK updated the exemptions page on 6 August 2026 to confirm the change.
Are small developments exempt from BNG?
Small ("minor") developments have been subject to BNG since 2 April 2024, so they are not exempt as a category. However, from 6 August 2026 any development on a site of 0.2 hectares or below is exempt if it does not impact priority habitat, and the de minimis rule exempts very small habitat impacts. Small developments that remain in scope can use the simplified small sites metric.
Do I need to prove my development is exempt?
Yes. You must state on the planning application form that you consider the development exempt and give reasons. For the de minimis exemption the Planning Practice Guidance strongly encourages plans showing the habitat inside the red line and how much is impacted, and where it is not clear, a completed metric for pre- and post-development value. The local planning authority checks the claim at validation.
Sources
Official guidance this page relies on, with the "last updated" date shown on each source when this page was written. Always check the live GOV.UK page before acting.
- Biodiversity net gain: exempt developments — GOV.UK (Defra) (updated 6 August 2026)
- Biodiversity net gain — Planning Practice Guidance (MHCLG) (updated 31 July 2026)
- Understanding biodiversity net gain — GOV.UK (Defra) (updated 14 July 2026)