Biodiversity net gain (BNG) has been mandatory for most development in England since 2024, and in 2026 the Government confirmed a package of reforms that changes who has to deliver it. If you are preparing a planning application — or a sustainability statement to support one — the new exemptions could remove a significant obligation from your scheme, or leave it firmly in place. This guide explains the 2026 BNG changes and what they mean in practice.
A quick recap: what BNG requires
Under the Environment Act 2021, most planning permissions in England must deliver a measurable 10% biodiversity net gain — leaving habitat in a better state after development than before. Gains are measured with the statutory biodiversity metric and secured for at least 30 years, following a mitigation hierarchy: avoid harm first, then enhance on-site, then deliver gains off-site, and only as a last resort buy statutory biodiversity credits. If you are new to the requirement, our guide on delivering 10% BNG on a small site walks through the mechanics.
What the Government announced in 2026
In April 2026 the Government published a set of updates intended to streamline how BNG works, reduce the burden on small and low-impact schemes, and extend it to major infrastructure. The changes are being introduced in stages through 2026.
Changes expected by 31 July 2026
- A new 0.2 hectare area-based exemption. Development below this footprint threshold would fall outside mandatory BNG.
- Removal of the self-build and custom-build exemption. That carve-out is being withdrawn, so some self-builds that were previously exempt will now be in scope.
- Temporary permissions exempted. Permissions granted for a maximum of five years would not need to deliver BNG.
- A simpler hierarchy for minor development. For minor schemes, off-site biodiversity gains would be given the same preference as on-site habitat creation, giving small developers more flexibility.
Taken together, the Government expects these changes to exempt around half of residential planning permissions from mandatory BNG — a substantial shift aimed squarely at speeding up housing delivery.
Changes later in 2026
- BNG extended to major infrastructure. Biodiversity net gain will apply to Nationally Significant Infrastructure Projects (NSIPs) from 2 November 2026.
- A brownfield consultation. The Government has consulted on a further targeted exemption for brownfield residential development, supporting its brownfield-first approach.
Why the changes now?
The reforms sit within a wider push to accelerate housing delivery. In its first two years, mandatory BNG added time and cost to small applications, and the metric and off-site unit market proved harder for minor developers to navigate than for large housebuilders. The 2026 package tries to keep BNG focused where it delivers most for nature — larger schemes and infrastructure — while lifting the administrative burden from the smallest sites. For applicants, the effect is a more forgiving regime for minor development, but a broader one for major projects, which now takes in nationally significant infrastructure for the first time.
Exempt from BNG does not mean exempt from sustainability
This is the point that catches applicants out. Even where a scheme falls outside mandatory BNG, biodiversity and green infrastructure remain material planning considerations. Local plans routinely require net gains for nature, protection of existing habitat and features, and landscape or greening measures — independent of the statutory 10% rule. In London, the Urban Greening Factor (London Plan Policy G5) sets a separate expectation for on-site greening that is unaffected by these exemptions.
A well-prepared sustainability statement is where all of this is drawn together: how the scheme responds to biodiversity policy (statutory or local), water efficiency, energy, and greening. Removing the statutory BNG obligation simplifies one part of that story — it does not remove the need to show a genuinely sustainable design.
What the 2026 changes mean for your application
- Check whether you are still in scope. The 0.2ha threshold and the removal of the self-build exemption change the answer for a lot of small schemes — confirm your position before assuming BNG does or does not apply.
- Do not treat an exemption as a free pass. Councils will still expect biodiversity and greening measures through local policy; a bare site with no ecological response can still attract objections.
- Evidence the exemption. Where you rely on an exemption, say so clearly and show why it applies — validation teams will look for it.
- Plan for local greening standards. In London especially, the Urban Greening Factor and local biodiversity policies continue regardless.
How Fortress Associates can help
Fortress Associates prepares automated sustainability statements for planning applications across every UK local authority. Each report covers biodiversity net gain, water efficiency against the 110 litres per person per day standard, urban greening and BREEAM where required — drawing the relevant national and local policy together for your site. The report is free and ready in minutes. To get started, contact us or explore our full range of planning services.
Sources & further reading
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