What changed — and why an old note may need reviewing
BNG changes in August 2026 mean a previous exemption assessment may no longer answer the right question. Before submitting an application in England, check the current rules against the actual proposal and application date.
Defra’s updated guidance introduces an exemption for developments with a red-line site area of 0.2 hectares or below. It also covers wholly temporary developments with permission for five years or less. Both started on 6 August 2026.
However, the small-area, temporary and de minimis exemptions do not apply where the development impacts on-site priority habitat. The separate self-build and custom-build exemption ended for new applications made on or after that date. Earlier applications and variations need their own transitional check.
Use one short evidence register
The useful next step is to connect each assumption to a document. Ask the project team to complete this register before relying on an exemption.
| Check | Evidence to retain |
|---|---|
| Application route and date | The submission record, permission history and any proposed variation. |
| Site area | A measured, dated red-line plan matching the application. |
| Habitat and impact | Appropriate ecological evidence showing what is present and what the works affect. |
| Temporary proposal | The whole proposal, requested duration and reinstatement assumptions. |
| Other requirements | A separate list of ecology, species, tree and planning obligations. |
A small boundary change can change the question
For example, imagine a design gains an access strip shortly before submission. The building footprint stays the same, but the application boundary changes. This is an illustrative situation, not an ACP case study.
First, remeasure the submitted red-line area. Then ask the ecologist whether the access works alter the habitat impact assessment. Finally, update the exemption note and drawing references together. An earlier email saying “small site” should not become the permanent justification.
Keep exemption and environmental responsibility separate
A BNG exemption does not establish that a site has no ecological constraints. Protected species, designated sites, planning policies and tree matters may still affect the proposal. Therefore, ask what evidence the authority needs for those issues as well.
Also, keep the scope proportionate. The purpose is to identify the right work before commissioning a full package. Explain any uncertainty clearly, including who will resolve it and when.
Our BNG service guide explains the wider process. For a site-specific discussion, send ACP the location, application stage and current plan.
Source and scope
England; checked 10 October 2026. Read Defra’s current BNG exemption guidance, including the full transitional provisions. This article is a practical coordination checklist, not a determination that a particular development is exempt.