Last updated: August 29, 2026
Quick Answer: From 6 August 2026, minor developments subject to mandatory Biodiversity Net Gain (BNG) no longer need to demonstrate that onsite habitat creation was considered before using registered offsite gains. This BNG offsite flexibility for August 2026 UK small developers is the most significant practical change in the reforms, removing a procedural hurdle that previously made offsite delivery more complex for sites just above the 0.2 hectare exemption threshold.
Key Takeaways
- From 6 August 2026, the statutory biodiversity gain hierarchy has been relaxed for minor (non-major) developments, meaning offsite units are now treated on equal footing with onsite habitat creation.
- Developments on sites of 0.2 hectares or less are fully exempt from mandatory BNG, provided no onsite priority habitat is affected and the application was submitted on or after 6 August 2026.
- The self-build and custom-build planning exemption from BNG has been removed from 6 August 2026; however, many such projects will fall under the new 0.2 ha size exemption.
- Offsite biodiversity units are currently priced at roughly £15,000 to over £35,000 per unit depending on habitat type, distinctiveness, and location. [10]
- Around 197 registered biodiversity gain sites offering approximately 28,000 units are available nationally as of August 2026. [6]
- Offsite units must still be registered on the biodiversity gain site register and secured through a legal mechanism such as a section 106 agreement or conservation covenant. [5]
- Mandatory BNG for Nationally Significant Infrastructure Projects (NSIPs) begins in November 2026, which is expected to increase demand and potentially tighten the offsite unit market. [8]
- Developers should engage with habitat banks early to lock in unit prices before NSIP demand enters the market later in 2026.
What Is Biodiversity Net Gain Offsite Flexibility?
Biodiversity net gain offsite flexibility refers to the ability of a developer to meet their mandatory 10% BNG requirement by purchasing registered offsite biodiversity units, without first having to prove that onsite habitat creation or enhancement was maximised or even considered. Under the original BNG framework introduced in England, the statutory gain hierarchy required developers to prioritise onsite delivery before turning to offsite options. [1]
The 6 August 2026 reforms change this for minor developments. Applicants can now go directly to offsite units to satisfy their BNG obligation, making the process faster and more commercially straightforward for smaller schemes. [4]
When Does BNG Offsite Flexibility Start in the UK?
The offsite flexibility provisions took effect on 6 August 2026 for all planning applications submitted on or after that date. [4] Applications submitted before 6 August 2026 remain subject to the previous hierarchy rules, so the transition date matters.
Defra confirmed the changes through amendments to the statutory BNG framework, with transitional arrangements published in July 2026. [4] Local planning authorities are expected to apply the new rules immediately for qualifying applications received from that date onwards.
BNG Offsite Flexibility August 2026: How the Changes Work for Small Developers
For minor developments, broadly those that do not meet the threshold for "major development" under the Town and Country Planning (Development Management Procedure) Order, the statutory biodiversity gain hierarchy has been relaxed so that offsite gains are treated equally with onsite creation. [4][7]
In practice, this means:
- A developer of a scheme with, say, eight dwellings on a 0.3 ha brownfield site can now plan from the outset to purchase offsite units rather than designing in onsite habitat features.
- There is no longer a requirement to submit evidence that onsite enhancement was explored and found insufficient before offsite units are accepted by the local planning authority.
- The ecologist must still run the statutory metric to calculate the biodiversity unit shortfall, and a biodiversity gain plan must still be submitted for approval. [1][5]
- Offsite units purchased must be recorded on the biodiversity gain site register to count toward the mandatory 10% target. [5]
This is a meaningful shift for BNG for small development projects, where onsite land constraints often make meaningful habitat creation impractical.
What Counts as a Small Developer for BNG Rules?
There is no single statutory definition of "small developer" in the BNG regulations, but the reforms use development scale as the practical dividing line. The key thresholds are:
| Development Type | BNG Status from 6 Aug 2026 | Offsite Hierarchy Rule |
|---|---|---|
| Site 0.2 ha or less (no priority habitat) | Exempt from mandatory BNG | Not applicable |
| Minor development above 0.2 ha | Mandatory BNG applies | Offsite equal to onsite, no prior justification needed |
| Major development | Mandatory BNG applies | Original hierarchy still applies |
Minor development typically covers residential schemes of fewer than 10 dwellings or commercial floorspace below 1,000 m². [7] The 0.2 ha exemption effectively removes BNG obligations for many small infill schemes, but those just above this threshold, say, a 0.25 ha site with six houses, are now the primary beneficiaries of the offsite flexibility rules. [2]
The 0.2 Ha Exemption, Self-Build Removal, and What Changed on 6 August 2026
The August 2026 BNG reforms made several simultaneous adjustments that interact with each other:
New 0.2 ha small-site exemption: Developments on sites no larger than 0.2 hectares are exempt from mandatory BNG, provided the application is submitted from 6 August 2026 and the development does not impact onsite priority habitat. [1][4] This covers a significant share of small infill residential and minor commercial schemes.
Removal of self-build and custom-build exemption: Prior to 6 August 2026, self-build and custom-build housing had a specific exemption from mandatory BNG. That exemption has been removed. [7] Self-build applicants submitting planning applications from 6 August 2026 are now subject to BNG requirements, unless their site falls within the new 0.2 ha threshold, which will cover many single-plot self-build projects.
Temporary development exemption confirmed: Developments granted planning permission for five years or less remain exempt from BNG. [7]
For a self-build developer on a 0.15 ha plot, the practical outcome is neutral: the 0.2 ha exemption likely applies, and no BNG obligation arises. For a self-build on a 0.4 ha plot, the picture changes, BNG now applies, and the offsite flexibility rules become relevant.
See the BNG changes from 6 August 2026 explained for developers and planners for a full breakdown of all exemption changes.
Offsite vs Onsite BNG: Which Is Cheaper for Small Developers?
There is no universal answer, but offsite delivery is often more cost-predictable for minor developments. Onsite habitat creation requires land allocation, ecological design, long-term management agreements, and monitoring costs spread over 30 years. For a small site where every square metre of land has development value, dedicating space to habitat can be commercially damaging.
Offsite unit cost benchmarks (August 2026): [10]
- Broad-leaved woodland units: approximately £15,000,£22,000 per unit
- Grassland and wetland units: approximately £20,000,£35,000+ per unit
- Prices vary by habitat distinctiveness, geographic location, and whether units are pre-sold or purchased from stock
For a minor development needing, say, three biodiversity units, total offsite costs could range from £45,000 to over £100,000 depending on habitat type. This is a material viability consideration, and early engagement with habitat banks to lock in pricing is now a standard recommendation from consultants. [6][10]
For a detailed comparison of delivery routes, see biodiversity net gain off-site or on-site delivery.
BNG Offsite Flexibility Requirements and Conditions
The relaxation of the gain hierarchy does not remove all procedural requirements. Offsite BNG for minor developments still requires:
- A completed statutory metric calculation showing the biodiversity unit shortfall that offsite gains must address. [1]
- A biodiversity gain plan submitted to and approved by the local planning authority before development commences. [5]
- Registration of the offsite gain site on the national biodiversity gain site register. [5]
- A legal agreement securing the offsite gains, typically a section 106 agreement or conservation covenant between the habitat bank operator and the relevant authority. [3][5]
- Geographic alignment, while there are no strict distance rules, local planning authorities may have preferences or policies on where offsite gains should be located relative to the development.
Common mistake: Assuming that because the hierarchy is relaxed, the biodiversity gain plan is optional or simplified. It is not. The plan remains a mandatory pre-commencement condition. [1]
For practical guidance on meeting these requirements, the guidance for developers on BNG sets out the key steps.
How to Find Approved Offsite BNG Schemes Near You
Registered biodiversity gain sites are searchable through the national biodiversity gain site register maintained by Natural England. As of August 2026, approximately 197 registered sites offering around 28,000 units are available nationally. [6]
Practical steps to find and secure offsite units:
- Search the Natural England biodiversity gain site register for registered sites in your local planning authority area or wider county.
- Contact habitat bank operators directly to check unit availability, habitat type, and pricing before finalising your metric calculations.
- Engage your ecologist early to identify the habitat types your metric requires, so you can match those to available units.
- Factor unit procurement timelines into your project programme, legal agreements can take several weeks to finalise.
The BNG off-site land banking vs habitat banking guide explains the difference between these supply routes and how to evaluate them.
Is Offsite BNG Mandatory or Optional for Small Developers?
Offsite BNG is optional, not mandatory, for minor developments. The relaxation of the gain hierarchy means developers can choose offsite delivery without needing to justify that choice, but they are equally free to deliver gains onsite or through a combination of both routes. [4][7]
Choose offsite if:
- The site has limited land available for habitat creation
- Onsite habitat features would reduce the developable area or net development value significantly
- The site is brownfield with low baseline biodiversity, making onsite gains harder to achieve cost-effectively
- Speed and certainty of BNG compliance are priorities
Choose onsite if:
- The site has green space that can be enhanced at low cost
- The local planning authority has strong preferences for onsite delivery
- Long-term management of onsite habitat is feasible and commercially acceptable
For small developers, the combination route, partial onsite, partial offsite, often provides the best balance of cost and planning acceptability. [2]
The November 2026 NSIP Connection and What It Means for Unit Supply
Mandatory BNG for Nationally Significant Infrastructure Projects begins in November 2026. [8] This is directly relevant to small developers relying on the offsite unit market, because NSIPs, major roads, energy projects, and large infrastructure schemes, will begin competing for the same registered biodiversity gain sites that currently serve the residential and commercial development market.
Industry analysis suggests that NSIP demand could tighten unit supply and push prices upward from late 2026 into 2027. [6][8] With approximately 28,000 units currently registered nationally, the market has capacity, but large infrastructure projects can require significant unit volumes. [6]
The practical implication for small developers: If you are planning a minor development that will rely on offsite BNG, securing units and agreeing prices before November 2026 is a commercially sensible step. Early engagement with habitat bank operators is now a standard part of pre-application due diligence. [10]
A Defra consultation launched in April 2026 also considers a targeted exemption for residential brownfield development, which could reduce offsite demand from the smallest urban sites if implemented. [9] However, this remains a proposal and has not yet been enacted.
BNG Offsite Flexibility: Common Mistakes to Avoid
1. Assuming the 0.2 ha exemption applies without checking for priority habitat. The exemption only applies if the development does not impact onsite priority habitat. A site with even a small area of protected grassland or wetland may not qualify. Always commission a preliminary ecological appraisal first. See how to conduct a biodiversity impact assessment.
2. Treating the hierarchy relaxation as removing the biodiversity gain plan requirement. The gain plan is still a pre-commencement condition for all minor developments subject to BNG. [1][5]
3. Purchasing offsite units from an unregistered site. Units must be on the national biodiversity gain site register to count toward the mandatory 10% target. [5] Verify registration status before entering any commercial agreement.
4. Ignoring the legal agreement requirement. Offsite gains must be secured through a section 106 or conservation covenant. A commercial agreement with a habitat bank operator alone is not sufficient. [3]
5. Leaving unit procurement to the last minute. With NSIP demand entering the market in November 2026, unit prices and availability may shift. Early procurement protects viability. [8][10]
FAQ
What is the BNG offsite flexibility introduced in August 2026?
From 6 August 2026, minor developments no longer need to demonstrate that onsite habitat creation was considered or maximised before using registered offsite biodiversity units. Offsite gains are now treated on equal footing with onsite delivery for non-major development applications. [4]
Does the 0.2 ha exemption apply to all development types?
The exemption applies across use classes where the site is 0.2 hectares or less and the development does not impact onsite priority habitat. It applies to applications submitted on or after 6 August 2026. [1][4]
Are self-build projects now subject to BNG?
Yes. The specific self-build and custom-build exemption was removed from 6 August 2026. However, many single-plot self-build projects will fall under the new 0.2 ha size exemption and therefore remain outside mandatory BNG in practice. [7]
How much does offsite BNG typically cost for a small development?
Offsite biodiversity units are broadly priced between £15,000 and over £35,000 per unit as of August 2026, depending on habitat type and location. A minor development requiring three units could face total offsite costs of £45,000 to over £100,000. [10]
Do I still need a biodiversity gain plan if I use offsite units?
Yes. A biodiversity gain plan must still be submitted and approved by the local planning authority before development commences, regardless of whether BNG is delivered onsite, offsite, or through a combination. [1][5]
When does mandatory BNG apply to infrastructure projects?
Mandatory BNG for Nationally Significant Infrastructure Projects (NSIPs) begins in November 2026. This is expected to increase demand for registered offsite units and may affect pricing and availability in the wider market. [8]
Conclusion
The BNG offsite flexibility introduced on 6 August 2026 is a genuinely practical reform for UK small developers. Removing the requirement to justify offsite delivery before using registered units cuts procedural complexity for minor developments, particularly those on sites just above the 0.2 ha exemption threshold. Combined with the new small-site exemption, the removal of the self-build exemption, and a growing national supply of registered habitat bank units, the August 2026 changes reshape the compliance landscape for smaller schemes.
Actionable next steps for small developers:
- Confirm whether your site qualifies for the 0.2 ha exemption by commissioning a preliminary ecological appraisal to check for priority habitat.
- If BNG applies, engage an ecologist immediately to run the statutory metric and identify your unit shortfall.
- Contact registered habitat bank operators now to check unit availability and lock in pricing ahead of NSIP demand entering the market in November 2026.
- Ensure your legal team is briefed on the section 106 or conservation covenant requirements for offsite gains.
- Monitor the Defra brownfield exemption consultation outcome, which could affect viability calculations for urban sites.
For further guidance on navigating these changes, see benefitting nature as a developer with biodiversity surveyors and the guide to biodiversity credits for developers.
References
[1] Understanding Biodiversity Net Gain – gov.uk
[2] BNG Changes 6 August 2026 Small Site Exemption What Every Developer And Planner Must Know Now – Bng changes 6 august 2026 small site exemption what every developer and planner must know now
[3] Guidance For Applicants Implementing BNG V1 3 April 2025 – wyre.gov.uk
[4] Biodiversity Net Gain Amendments And Transitional Arrangements Published – defraenvironment.blog.gov.uk
[5] Biodiversity Net Gain – gov.uk
[6] BNG Habitat Bank Supply August 2026 197 Registered Gain Sites 28000 Units And What UK Developer Procurement Looks Like Now – Bng habitat bank supply august 2026 197 registered gain sites 28000 units and what uk developer procurement looks like now
[7] New Biodiversity Net Gain Exemptions From August 2026 What Developers Need To Know – footanstey.com
[8] BNG Net Gain Reset NSIP Defra April 2026 – oakbankgc.co.uk
[9] Biodiversity Net Gain Considering A Targeted Exemption For Residential Brownfield Development – consult.defra.gov.uk
[10] Biodiversity Net Gain Units Market August 2026 What Landowners And Developers Need To Know – Biodiversity net gain units market august 2026 what landowners and developers need to know