If you submit planning applications regularly, you’ll know that Biodiversity Net Gain can be one of the more technical parts of the process.

From 6 August 2026, the rules are changing. Two new exemption options are being introduced, the existing self-build and custom-build exemption is being removed, and minor developments that remain subject to BNG will have more flexibility.

The changes were confirmed by the Department for Environment, Food & Rural Affairs following the publication of new regulations in July.

We’re updating Planda Portal so that applications submitted from 6 August reflect the new requirements.

A new exemption for developments of 0.2 hectares or below

The biggest change is a new exemption for developments where the site area within the red-line boundary is 0.2 hectares or below.

This means these developments will no longer be required to deliver mandatory Biodiversity Net Gain, provided no onsite priority habitat is negatively impacted.

Applicants selecting this exemption will need to confirm that the site meets the area requirement and that the development will not negatively impact any priority habitat.

The government expects the change to reduce the burden on the smallest developers and local authorities, while allowing more resources to be focused on developments with a greater impact and greater potential to deliver benefits for nature.

Some temporary developments are also exempt

A second exemption is being introduced for temporary developments.

From 6 August, BNG will not apply where the whole development is temporary and planning permission is granted for five years or less.

Any earlier planning permissions for the same temporary development must also be taken into account when considering the total period.

As with the new 0.2-hectare exemption, the development must not negatively impact any onsite priority habitat.

The self-build exemption is being removed

The existing exemption for self-build and custom-build development will no longer apply to new planning applications submitted from 6 August 2026.

That does not mean every self-build development will now be subject to mandatory BNG. Many may instead qualify under the new 0.2-hectare exemption, provided the relevant conditions are met.

Self-build and custom-build applications submitted before 6 August will continue to be assessed under the existing rules.

The government has confirmed that the changes generally apply only to new applications made from 6 August. Applications and permissions already in progress will continue to follow the previous BNG legislation.

Minor developments will have more flexibility

The biodiversity gain hierarchy is also changing for minor developments that remain subject to BNG.

Under the new rules, minor developments that are not exempt, including sites above 0.2 hectares, will be able to choose offsite biodiversity delivery from the outset.

This should make the process more flexible for smaller sites where delivering the full BNG requirement onsite may not be practical.

What we’re changing in Planda Portal

We’re updating the Environmental Details section to include the two new exemption options and the questions needed to confirm eligibility.

Applicants will be able to select:

• Developments of 0.2 hectares or below

• Temporary developments permitted for five years or less

For both exemptions, applicants will also be asked to confirm that no onsite priority habitat will be negatively impacted.

The existing self-build and custom-build exemption will be removed for new applications subject to the updated rules.

The de minimis exemption will remain available. Where a development qualifies for the new 0.2-hectare exemption, applicants may find that option simpler to demonstrate.

What applicants and agents need to do

Anyone with a draft application that they plan to submit on or after 6 August should review the Biodiversity Net Gain section before submitting.

You may need to select a new exemption, answer additional eligibility questions or update an application that currently relies on the self-build and custom-build exemption.

The updated questions will be available in Planda Portal from 6 August 2026.

Exemption does not mean biodiversity can be ignored

Mandatory BNG may be changing for the smallest developments, but exemption from the national requirement does not remove wider responsibilities towards biodiversity.

East Devon District Council explains:

“Even where planning application sites are exempt from the national mandatory 10% BNG requirement, EDDC still expects applicants to achieve a net gain and other biodiversity enhancements.”

Existing wildlife legislation, national planning policy and local planning policies will continue to apply. Applicants should still consider biodiversity early, avoid environmental harm wherever possible and incorporate nature-friendly features into their proposals.

As always, our aim is to make planning applications easier to complete and less likely to come back with avoidable questions.