Does mandatory BNG apply to your scheme?
Eight quick questions covering the exemptions that apply in England from 6 August 2026, including the 0.2 hectare small sites exemption, temporary permissions and NSIPs.
Email me my result and next steps
We will send the result, the rules it is based on and what to do next. If your scheme is in scope we can start sourcing units straight away.
Free for developers. Your details are only used to source your units.
An indicative guide only, not legal or planning advice. Confirm with your ecologist and planning authority. Rules last checked against gov.uk on 3 October 2026.
How the checker works
Mandatory biodiversity net gain applies to most planning permissions in England, with exemptions set out in the Biodiversity Gain Requirements (Exemptions) Regulations. The checker walks through the main exemptions in order and gives one of three results: likely exempt, likely in scope or check with your ecologist. In-scope results lead straight into the sourcing check.
It is an indicative guide only, not legal or planning advice. Confirm with your ecologist and planning authority. The rules it uses were last checked against gov.uk on 3 October 2026. Read the full guide: Do I need BNG?
The exemptions in one table
| Exemption | Test | Notes |
|---|---|---|
| Small sites | 0.2 hectares or less and no on-site priority habitat negatively affected | From 6 August 2026; replaces the self-build exemption |
| Temporary development | Permission for five years or less with reinstatement | Multiple permissions for the same development count together |
| Householder | Extensions and outbuildings for a single home | Unchanged |
| De minimis | Less than 25 square metres of habitat or 5 metres of hedgerow affected | Unchanged |
| Gain sites | Development that is itself habitat creation for BNG | Unchanged |
| NSIPs | Applications before 2 November 2026 not caught | From that date, 10% with no sector exemptions |
If your scheme is in scope
You need a statutory biodiversity metric, a statement of how the gain hierarchy was considered and, after permission, an approved biodiversity gain plan before work starts. Where the metric shows an off-site deficit, buy units from a registered gain site. Minor development can use off-site units without proving on-site options are exhausted. The sourcing check takes it from there.
What changed on 6 August 2026?
Sites of 0.2 hectares or less became exempt unless on-site priority habitat is negatively affected, the self-build and custom build exemption was removed, temporary permissions of up to five years became exempt where the land is restored and for minor development off-site gains were put on an equal footing with on-site gains.
Is brownfield development exempt?
Not yet. A consultation on a targeted exemption for residential brownfield development ran from 15 April to 10 June 2026. Until the government responds, brownfield sites remain in scope. Our brownfield tracker is updated when the position changes.
Do NSIPs need BNG?
Mandatory BNG applies to onshore NSIP applications in England submitted on or after 2 November 2026, with a consistent 10% requirement and no sector-specific exemptions.