On 6 August 2026, a significant set of amendments to the Biodiversity Net Gain (BNG) regime came into force in England. The Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026 mark the biggest recalibration of BNG since it became mandatory for major development in February 2024 – and for smaller schemes in particular, the changes are substantial.
Here’s what’s changed, what hasn’t, and what it means if you’re bringing forward a planning application.
Four changes, effective from 6 August
- A new small-site exemption. Developments of 0.2 hectares (2,000 m²) or below are now exempt from mandatory BNG — provided the site does not affect on-site priority habitat. This is a blanket exemption based on the site area within the red line boundary, and it’s expected to remove a large number of minor residential and commercial schemes from the BNG regime entirely.
- A temporary development exemption. Developments consisting wholly of temporary planning permissions requiring reinstatement — where the permission runs for five years or less — are now also exempt.
- The self-build and custom-build exemption is abolished. This is the change most likely to catch people out. Self-build and custom-build dwellings previously sat outside the BNG regime. That exemption has now been removed. Any self-build or custom-build application determined on or after 6 August must deliver the standard 10% biodiversity net gain, unless it separately qualifies for the new 0.2ha exemption above.
- A relaxed hierarchy for non-major development. Under the original regime, applicants had to demonstrate that on-site habitat opportunities had been maximised before turning to off-site biodiversity units. From 6 August, this on-site-first requirement applies only to major development (broadly: 10+ dwellings, sites of 0.5ha+, 1,000m²+ of floorspace, or 1ha+ sites, plus minerals and waste development). For everything else, off-site gains and on-site creation now sit on equal footing — applicants no longer need to justify going off-site first.
The transitional point that matters most
These changes apply to applications submitted from 6 August 2026 onwards. Anything already submitted — including permissions where a section 73 variation is anticipated — remains subject to the existing BNG rules as they stood before 6 August. For live applications, it’s worth checking the submission date against this cut-off before assuming a new exemption applies.
What’s still to come
Not all of the changes Defra flagged in its April 2026 response have landed yet. Still in the pipeline:
- An exemption for development whose primary purpose is to conserve or enhance biodiversity
- A targeted exemption for development enhancing parks, playing fields and public gardens
- A possible additional exemption for certain residential brownfield development (consultation closed 10 June 2026, outcome pending)
- Mandatory BNG for Nationally Significant Infrastructure Projects, expected from 2 November 2026, with flexibility to aggregate off-site delivery across affected Local Planning Authority areas
What this means in practice
For smaller developments, the practical effect is a lighter compliance burden: many sub-0.2ha schemes will now avoid mandatory BNG altogether, and non-major schemes have more flexibility in how they meet the 10% requirement. That’s a welcome simplification for SME developers and sites where on-site enhancement was always going to be impractical.
But two things are worth flagging to clients early:
- Self-builders need to check their position now. A scheme that would once have sailed through exempt may now need a full BNG assessment — unless it happens to qualify under the new 0.2ha rule.
- Exemption eligibility still requires evidence. Falling under 0.2ha or avoiding priority habitat isn’t self-certifying — it needs to be confirmed through proper habitat assessment, and local planning authorities will still weigh biodiversity impact when determining applications even where BNG itself doesn’t formally apply.
As ever, the detail will matter site by site. If you’re unsure how these changes affect a live or upcoming application, our ecology and planning team can help you work through eligibility and next steps.
Author: Emily Snape Gormley
Sources: Defra Environment blog; The Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026, SI 2026 No. 790; CLA guidance note, August 2026.
