Biodiversity Net Gain changed materially in August 2026, but the year's reforms are not finished.
Four changes took effect on 6 August 2026, altering exemptions and simplifying the biodiversity gain hierarchy for qualifying non-major development.
Then, from 2 November 2026, mandatory BNG extends to nationally significant infrastructure projects (NSIPs) in England. Developers applying for a Development Consent Order on or after that date will need to deliver at least 10% biodiversity net gain.
Taken together, the changes reduce the regulatory burden on some of the smallest developments while bringing some of England's largest infrastructure projects into mandatory BNG for the first time.
1. Developments of 0.2 hectares or less may now be exempt
From 6 August 2026, BNG does not apply to planning applications for developments where the red-line site area is 0.2 hectares or below, provided the development does not impact an on-site priority habitat.
The exemption applies to applications made on or after 6 August 2026.
For developers, this creates a useful early-stage test: establish the red-line site area and check for priority habitat before assuming that a full BNG process is required.
2. Temporary developments may now be exempt
From 6 August 2026, qualifying temporary development can also be exempt where the whole development is temporary, planning permission is granted for five years or less, and no on-site priority habitat is affected.
The exemption is intended for genuinely temporary development. Where the relevant conditions are not met, the ordinary BNG rules continue to apply.
3. The self-build and custom-build exemption has been removed
The separate exemption for self-build and custom-build development no longer applies to new planning applications made on or after 6 August 2026.
Those developments are now considered under the general BNG rules and may still qualify for another exemption — including the new 0.2-hectare threshold — depending on the circumstances.
4. Qualifying non-major developments can consider on-site and off-site delivery at the same time
For qualifying non-major developments where the planning application is made on or after 6 August 2026, the biodiversity gain hierarchy has been simplified.
On-site enhancement, on-site creation and registered off-site biodiversity gains can now be considered at the same level of preference. The developer does not have to exhaust on-site creation or enhancement before considering registered off-site supply.
Avoidance and mitigation principles still apply, and statutory biodiversity credits remain the final option.
What this means for demand
The August reforms reduce the number of smaller developments that fall within mandatory BNG and simplify the route for qualifying non-major schemes.
That does not mean the off-site market disappears. Larger residential, commercial, logistics and infrastructure schemes remain subject to mandatory BNG, and developments that cannot satisfy their requirement on-site will continue to need registered off-site biodiversity units.
The composition of demand is therefore changing rather than the market simply switching off: fewer very small schemes, but continued demand from larger and more complex developments where unit requirements, geography, availability and procurement are more material.
What changes next: NSIPs from 2 November 2026
The next major change comes on 2 November 2026.
From that date, mandatory BNG applies to nationally significant infrastructure projects in England where the developer applies for a Development Consent Order (DCO) on or after 2 November.
Qualifying NSIPs must deliver at least 10% biodiversity net gain. They operate under the Planning Act 2008 framework rather than the ordinary town-and-country planning route, with specific biodiversity gain statements and NSIP guidance.
This matters commercially because it brings larger and often more complex infrastructure schemes into mandatory BNG. These projects may have significant unit requirements, complex geography and long programme timetables, making early identification of suitable off-site supply increasingly important.
Mandatory BNG begins for NSIPs
DCO applications made on or after this date must deliver at least 10% BNG in England.
What has not changed
For developments that remain in scope, the core BNG framework remains in place: the 10% minimum uplift, the Statutory Biodiversity Metric, the requirement to secure relevant gains for at least 30 years, the Biodiversity Gain Sites Register, legal mechanisms including conservation covenants and section 106 agreements, the habitat trading rules and the role of statutory biodiversity credits as a last resort.
The August reforms do not change nutrient neutrality or water-credit requirements, which operate through separate regulatory and market frameworks.
What developers should do now
For new sites, check BNG status early — before assuming a full assessment is required. Confirm the red-line area, whether priority habitat is affected and whether any exemption applies.
For qualifying non-major schemes, consider on-site and registered off-site delivery together rather than treating off-site procurement as a last-minute exercise.
For larger development and infrastructure projects, identify likely off-site requirements and supply options early enough that BNG procurement does not become part of the planning critical path.
And for NSIPs approaching a DCO application after 2 November 2026, build mandatory BNG into the consenting and procurement strategy now.
Use the Verdaq BNG Exemption Checker to assess whether a development may fall within one of the statutory exemptions.
Need off-site BNG?
Upload the Statutory Biodiversity Metric or submit your requirement through Verdaq to identify potentially suitable supply and compare provider options.
Verdaq Research · September 2026. This briefing is general information, not legal or planning advice.