Guide
Biodiversity net gain requirements: what gov.uk actually says
Updated
BNG is a statutory scheme under the Environment Act 2021. This page states the requirements as gov.uk states them, with nothing added.
The core requirements
- The gain
- gov.uk: developers must deliver a BNG of 10 percent. The purpose is that habitats are in a measurably better state than they were before the development.
- The measurement
- gov.uk: there is a statutory biodiversity metric which you must use to measure biodiversity units, using the statutory biodiversity metric tool.
- The plan
- gov.uk: you will need to create a biodiversity gain plan showing how you will achieve BNG, and the local planning authority must approve or refuse it within 8 weeks.
- The duration
- gov.uk: you must maintain the habitats you create or enhance for a minimum of 30 years, with responsibilities set out in a legal agreement.
- Where it applies
- The guidance applies to England.
The delivery hierarchy
- Create habitat on site. The first option, and normally the cheapest unit available to a scheme.
- Off-site units. Deliver gains on other land you control, or buy units from a habitat bank or landowner. gov.uk notes that from 6 August 2026 small (minor) developments that are not already exempt can consider options 1 and 2 at the same time.
- Statutory biodiversity credits bought from the government, described by gov.uk as a last resort. Prices are published, and 2 credits must be bought for every 1 biodiversity unit compensated for.
The commencement dates
| Development type | Date stated on gov.uk |
|---|---|
| General mandatory requirement | 12 February 2024 |
| Small (minor) developments | Applications made before 2 April 2024 are exempt |
| Nationally Significant Infrastructure Projects | 2 November 2026 |
| Site area threshold change to 0.2 hectares | From 6 August 2026 |
Small sites
gov.uk states that for small developments you do not need an ecologist: you can either use the simpler small sites biodiversity metric tool yourself, or someone familiar with the site can do a survey and make a calculation. That is a genuine cost saving, but it is worth being honest about the trade-off: a metric calculation that a local planning authority queries costs more in delay than a consultant's fee saved, and habitat condition assessment is the part non-specialists most often get wrong.
Quoted requirements are taken from gov.uk guidance on understanding biodiversity net gain, linked in the sources below. The underlying statute is the Environment Act 2021. Check the gov.uk page before relying on any summary, including this one, because BNG guidance has changed more than once since 2024.