Do I need BNG? Who mandatory biodiversity net gain applies to
If you need planning permission in England and your development is not exempt, you need to deliver a 10% biodiversity net gain secured for at least 30 years. From 6 August 2026 sites of 0.2 hectares or less with no priority habitat affected, temporary permissions of five years or less and householder development are exempt. NSIPs are caught from 2 November 2026.
Key facts
- Mandatory BNG applies to major development since 12 February 2024 and minor development since 2 April 2024.
- From 6 August 2026 (applications made on or after that date): 0.2 hectare small sites exemption unless on-site priority habitat is negatively affected; temporary permissions of up to five years exempt where the land is restored; self-build and custom build exemption removed; equal footing for off-site gains on minor development.
- The government expects the 0.2 hectare exemption to exempt around 50% of residential permissions previously subject to BNG.
- Onshore NSIP applications submitted on or after 2 November 2026 need mandatory BNG with no sector-specific exemptions.
- A consultation on a residential brownfield exemption ran 15 April to 10 June 2026; no response when last checked.
Last checked: 3 October 2026
Which developments are in scope?
Most applications for planning permission under the Town and Country Planning Act 1990 in England, including new homes, commercial, industrial and energy schemes and from 2 November 2026 onshore nationally significant infrastructure projects consented through development consent orders.
Which developments are exempt?
| Exemption | Condition | Since |
|---|---|---|
| Sites of 0.2 hectares or less | No on-site priority habitat negatively affected | 6 August 2026 |
| Temporary development | Permission for five years or less and the land reinstated | 6 August 2026 |
| Householder development | Extensions and outbuildings for a single dwelling | 2024 |
| De minimis impact | Less than 25 square metres of habitat or 5 metres of hedgerow affected | 2024 |
| Biodiversity gain sites | Development that is itself habitat creation for BNG | 2024 |
| Self-build and custom build | Removed; may still qualify under the 0.2 hectare rule | Removed 6 August 2026 |
What changed for minor development?
For minor development only, which includes residential schemes of 9 or fewer dwellings on a site of 1 hectare or less, off-site gains now sit on an equal footing with on-site gains. You no longer have to evidence that on-site enhancement is not achievable before buying units. Major development still follows the biodiversity gain hierarchy. See minor development and off-site BNG.
What about brownfield sites?
A consultation on a targeted exemption for residential development on brownfield land, with thresholds up to 2.5 hectares, closed on 10 June 2026. The government had not responded when we last checked, so brownfield sites remain in scope. We track the position on the brownfield tracker.
How do I check my scheme?
Use the exemption checker for an indicative answer in a minute, then confirm with your ecologist and planning authority. If you are in scope and the metric shows an off-site deficit, the sourcing check starts the search for units.
How to decide quickly
- Is the application in England and made on or after 6 August 2026? If before, the previous rules apply.
- Is the site 0.2 hectares or less with no priority habitat negatively affected? Exempt.
- Is it a temporary permission of five years or less with reinstatement? Exempt.
- Householder or de minimis impact? Exempt.
- Otherwise in scope: 10% gain, 30 years, with the equal footing rule if it is minor development.
What being in scope means in practice
Your application needs a statutory biodiversity metric, a statement of how the gain hierarchy was considered and, after permission, an approved biodiversity gain plan before development starts. Where the metric shows an off-site deficit you buy units from a registered gain site or as a last resort statutory credits. Most small schemes need a fraction of a unit; most large schemes need several.
How the requirement is secured
Every planning permission in scope carries the general biodiversity gain condition by law. It requires an approved biodiversity gain plan before development begins and the approved plan is enforceable like any other condition. Off-site units are secured through the provider’s Section 106 agreement or conservation covenant and the allocation on the register; on-site habitat is secured by condition or a Section 106 agreement with a 30-year management plan.
Key takeaways
- Most planning permissions in England are in scope
- Three main exemptions: 0.2 hectare sites, temporary permissions, householder development
- Minor development can use off-site units on an equal footing
- NSIPs are caught from 2 November 2026
Frequently asked questions
Does BNG apply to applications submitted before 6 August 2026?
They are assessed under the previous rules, even if validated after that date.
Is a change of use in scope?
Usually yes if it needs planning permission and is not exempt, though many changes of use have de minimis habitat impact.
Does BNG apply in Wales or Scotland?
No. Mandatory BNG applies in England. Other nations have their own policies.
What if my site is 0.25 hectares?
In scope. The threshold is 0.2 hectares or less.
Is permitted development in scope?
Most permitted development is outside mandatory BNG. Prior approval routes vary; check with your planning authority.
Does BNG apply to a reserved matters application?
The requirement attaches to the outline permission. Reserved matters proceed under the condition already imposed.
Sources
- Biodiversity net gain exemptions, gov.uk
- Biodiversity net gain guidance, gov.uk
- Environment Act 2021, Schedule 7A, legislation.gov.uk
Written by BNG Sourced by Green Acres BNG specialists and reviewed by Mike Dungait, Managing Director of Green Acres BNG, who has registered and manages two habitat banks. Indicative information, not legal or planning advice. Confirm with your ecologist and planning authority.
Related: BNG sourcing check, exemption checker, BNG unit prices, glossary, the 0.2 hectare exemption, BNG for NSIPs.
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