Biodiversity Net Gain Reforms Confirmed: New 0.2ha Exemption and Self-Build Change From 6 August 2026

The UK Government has now confirmed the implementation date and detail of long-awaited reforms to the mandatory Biodiversity Net Gain (BNG) regime. The changes will apply to planning applications submitted on or after 6 August 2026, and represent a meaningful shift for small-site developers, self-builders and anyone bringing forward temporary schemes.

If you have a project in the pipeline, it is worth understanding how these reforms could affect your submission strategy - and, in some cases, whether it may be sensible to delay or resubmit an application to take advantage of the new exemptions.

What Is Changing?

The headline changes to the BNG regime are:

• A new exemption for developments where the total red line application boundary is 0.2 hectares or less.
• A new exemption for temporary developments granted planning permission for five years or less.
• Minor developments over 0.2 hectares will be able to deliver BNG off-site from the outset, rather than having to demonstrate on-site provision first.
• The existing self-build and custom-build exemption will be withdrawn for new applications submitted from 6 August 2026 onwards.

Taken together, these reforms are designed to reduce the administrative and cost burden of BNG on the smallest sites, while keeping the wider regime intact for larger schemes.

The Priority Habitat Caveat

The new 0.2 hectare exemption does not apply where a proposal would result in the loss or deterioration of priority habitat. That covers a fairly wide range of features often found on rural and edge-of-settlement sites, including traditional orchards, deciduous woodland, lowland meadows, species-rich grassland, heathland, reedbeds, priority ponds, certain wetlands, and qualifying species-rich hedgerows.

Many small sites will not contain any of these features, but it should never be assumed. An ecological assessment is the safest way to confirm whether the exemption is genuinely available before relying on it in a planning submission.

Transitional Arrangements

The new rules apply based on when an application is submitted, not when it is decided. Applications submitted before 6 August 2026 will continue to be assessed under the current BNG legislation, while those submitted on or after that date will benefit from the new exemptions where relevant.

For some small schemes, the mandatory BNG requirement can add significant cost or design constraints. If a project sits close to the 0.2 hectare threshold, or is otherwise likely to qualify for one of the new exemptions, there may be a case for withdrawing and resubmitting after the changes come into force - though that decision should always be weighed carefully against wider programme, validation and policy considerations.

Local Planning Policy Still Applies

An important point that is easy to miss: being exempt from statutory BNG does not mean biodiversity can be ignored. Local Plan policies and the National Planning Policy Framework still expect biodiversity impacts to be avoided where possible, minimised where they cannot be, and mitigated through appropriate enhancements as part of the development.

In practice, some Local Planning Authorities will continue to expect a biodiversity metric to demonstrate no net loss, or measurable gain, even where mandatory 10% BNG does not apply. Preliminary Ecological Appraisals, ecological mitigation strategies and biodiversity information are all likely to remain part of the standard package for many rural and edge-of-settlement sites.

Self-Build Developments

The existing self-build and custom-build exemption is one of the more significant losses in this reform. Anyone planning to rely on it should aim to submit their application before 6 August 2026, as it will no longer be available for new applications submitted on or after that date.

What This Means in Practice

For small-site developers and self-builders, the reforms open up a genuinely useful set of exemptions - but they also introduce a new layer of judgement around site boundaries, priority habitats and submission timing. Getting the strategy right at pre-application stage is likely to be more important than ever.

How LB Planning Can Help

If you are unsure how the BNG changes affect a live or upcoming application, whether your site is likely to qualify for the new 0.2 hectare exemption, or whether it makes sense to adjust submission timing, please get in touch. LB Planning can review your proposals and advise on the best route through the transition, working alongside ecological consultants where a Preliminary Ecological Appraisal or biodiversity metric is required.