Biodiversity Net Gain Changes July 2026: Small Sites, NSIPs and What Comes Next

Last updated: June 25, 2026

Quick Answer: By the end of July 2026, the government will introduce a new 0.2-hectare area-based BNG exemption, remove the self-build exemption, and level the hierarchy between on-site and off-site gains for minor developments. From 2 November 2026, mandatory BNG extends to all Nationally Significant Infrastructure Projects. These Biodiversity Net Gain changes July 2026 small sites NSIPs reforms represent the most significant recalibration of the BNG framework since mandatory requirements began in February 2024.

Key Takeaways

• Mandatory 10% BNG has applied to major developments since 12 February 2024 and to small/minor sites since 2 April 2024.
• A new 0.2-hectare area-based exemption arrives by end of July 2026, replacing the current small-scale self-build and custom-build exemption.
• Temporary planning permissions of up to 5 years will be exempted from BNG requirements under the July 2026 changes.
• The biodiversity gain hierarchy for minor development will treat off-site gains on equal footing with on-site habitat creation or enhancement.
• From 2 November 2026, BNG becomes mandatory for all NSIPs, which is expected to significantly increase demand for off-site biodiversity units.
• A consultation on brownfield residential exemptions up to 2.5 hectares closed on 10 June 2026; outcomes are pending.
• The statutory biodiversity metric, habitat baseline surveys, BNG plans, 30-year monitoring, and legal mechanisms (Section 106 or conservation covenants) remain the backbone of compliance for all site types.
• Landowners with suitable land should begin habitat bank registration processes now, ahead of NSIP-driven demand.

What Is Biodiversity Net Gain and Why Is It Changing in July 2026?

Biodiversity Net Gain (BNG) is a planning requirement that obligates developers to leave biodiversity in a measurably better state than before development. Under Schedule 14 of the Environment Act 2021, a minimum 10% net gain — calculated using the statutory biodiversity metric — must be demonstrated before planning permission can be granted in England.

The July 2026 changes respond to two pressures: evidence that the current exemption framework is poorly targeted, and the government's commitment to expand BNG to infrastructure. The DEFRA blog (April 2026) confirmed that the self-build exemption was being removed because it created an unintended loophole for small residential schemes, while the new area-based threshold offers a cleaner, more proportionate boundary. For a full grounding in how the framework operates, see this Biodiversity Net Gain explained guide.

How Will the July 2026 BNG Changes Affect Small Sites and NSIPs?

The Biodiversity Net Gain changes July 2026 small sites NSIPs reforms affect two distinct groups in different ways.

For small sites: The replacement of the self-build exemption with a 0.2-hectare area-based threshold creates a cleaner rule. Any development footprint under 0.2 hectares will be exempt, regardless of whether it is self-build or not. This means some projects that previously relied on the self-build exemption will lose it, while other small schemes gain a more straightforward route to exemption. Temporary permissions of up to five years are also exempted, which benefits short-term infrastructure, meanwhile uses, and certain agricultural conversions.

For NSIPs: From 2 November 2026, all Nationally Significant Infrastructure Projects — including nationally significant energy, transport, water, and waste schemes — must comply with mandatory BNG. The scale of these projects means their habitat loss calculations will generate very large unit requirements, and the expectation from both DEFRA and the RTPI is that this will place substantial upward pressure on the off-site biodiversity unit market. Developers and ecologists working on NSIPs should begin baseline surveys and unit procurement strategies immediately.

What Counts as a Small Site Under the New BNG Rules After July 2026?

Under the July 2026 reforms, the area-based threshold of 0.2 hectares becomes the primary determinant of small-site exemption status. A development with a total footprint below 0.2 hectares will be exempt from mandatory BNG requirements.

Key points to note:

• The 0.2-hectare threshold applies to the development footprint, not the overall site area.
• The existing de minimis exemption for developments affecting less than 25 square metres of habitat and fewer than five trees is unchanged.
• Irreplaceable habitats remain outside the standard metric calculation regardless of site size.
• The brownfield residential exemption (for sites up to 2.5 hectares) is still under consultation; no confirmed outcome was available as of 10 June 2026.

Developers should not assume that falling below 0.2 hectares removes all ecological obligations. Protected species surveys, Habitats Regulations Assessment screening, and local planning authority conditions may still apply. For a detailed breakdown of what applies to smaller schemes, see BNG for small development projects.

What Are the New BNG Requirements for Small Sites After July 2026?

Small sites that do not qualify for the 0.2-hectare exemption must still deliver 10% BNG using the statutory biodiversity metric. The process follows the same steps as for major developments:

1. Habitat baseline survey — a Phase 1 or extended Phase 1 survey to establish the pre-development habitat condition and area.
2. Statutory biodiversity metric calculation — using the current DEFRA metric tool to quantify habitat units before and after development.
3. BNG plan — a biodiversity gain plan submitted to and approved by the local planning authority before development commences.
4. Legal mechanism — gains must be secured for 30 years via a Section 106 agreement or conservation covenant.
5. 30-year monitoring — the responsible party must demonstrate habitat condition at agreed intervals throughout the management period.

The critical change for minor development after July 2026 is the hierarchy amendment. Previously, on-site delivery was preferred. Under the revised rules, off-site biodiversity gains carry equal weight in the hierarchy for minor development. This matters practically because many small sites have limited space for meaningful on-site habitat creation. For guidance on how to structure that decision, see Biodiversity Net Gain: off-site or on-site delivery?

Difference Between BNG Rules for Small Sites vs Large Developments in 2026

The 10% net gain requirement is identical across site sizes. The differences lie in the hierarchy, flexibility, and exemption thresholds.

The levelling of the hierarchy for minor development is arguably the most consequential practical change. It removes the obligation on small-site developers to demonstrate that on-site delivery is not feasible before turning to off-site options — a step that previously added cost and delay.

Do All NSIPs Need to Meet Biodiversity Net Gain Requirements from November 2026?

Yes. From 2 November 2026, BNG becomes mandatory for all Nationally Significant Infrastructure Projects in England. This includes energy generation and transmission, major road and rail schemes, airports, harbours, and water infrastructure above the relevant thresholds under the Planning Act 2008.

There are no confirmed blanket exemptions for NSIPs equivalent to the small-site thresholds. The scale of habitat loss associated with large infrastructure means that even a 10% net gain requirement will generate very large unit demands. Bird & Bird's analysis of the NSIP BNG framework notes that the off-site unit market — still relatively immature — will face significant strain. Landowners considering registering land as habitat banks should act before November 2026 to benefit from early-mover positioning. See how to sell biodiversity units for the registration process.

Which Small Site Projects Are Exempt from BNG in July 2026?

As of the July 2026 reforms, the confirmed exempt categories for small sites are:

• Developments with a footprint under 0.2 hectares (new area-based exemption).
• Developments affecting less than 25 square metres of habitat and fewer than five trees (existing de minimis exemption, unchanged).
• Temporary planning permissions of up to five years (new exemption from July 2026).
• Householder applications (unchanged exemption).
• Permitted development rights (unchanged exemption).

The self-build and custom-build exemption is removed by end of July 2026. Developers who have been relying on this route for small residential schemes must reassess their compliance position immediately.

The brownfield residential exemption (up to 2.5 hectares) remains under consultation. Until a formal outcome is published, it cannot be relied upon. For a current overview of exempt project categories, see exempt projects guidance.

How to Calculate BNG for Small Sites Under the New 2026 Rules

The calculation process for small sites uses the same statutory biodiversity metric as for major developments. The steps are:

1. Commission a habitat baseline survey to map and assess all habitats within the development footprint and a defined buffer.
2. Enter pre-development habitat data into the DEFRA metric tool, recording area, condition, and strategic significance.
3. Model the post-development habitat scenario, including any on-site creation or enhancement.
4. If the on-site result falls below 10%, identify off-site habitat units to close the gap (now treated equally in the hierarchy for minor development).
5. If off-site units are insufficient or unavailable, statutory biodiversity credits purchased from DEFRA act as a last resort.

For a worked example of what this assessment involves, see what is in a biodiversity net gain assessment.

Common mistake: Small-site developers often underestimate the condition scoring of existing habitats. A site with semi-improved grassland or scrub may have a higher baseline than expected, making the 10% uplift harder to achieve on-site alone. Getting the baseline survey right is the single most important step.

Alternatives to On-Site BNG for Small Projects

For minor development after July 2026, off-site delivery is now an equal first choice alongside on-site habitat creation. The practical options are:

• Off-site habitat units purchased from a registered habitat bank. The CLA has noted growing landowner interest in habitat banking as a revenue stream, particularly on lower-productivity agricultural land.
• Statutory biodiversity credits purchased directly from DEFRA as a last resort. These are priced at a significant premium to incentivise on-site and off-site delivery first. For a current understanding of how credit pricing works, see the guide to biodiversity credits for developers.
• Conservation covenants or Section 106 agreements can secure off-site gains on third-party land, with the landowner taking on the 30-year management obligation.

For a comparison of land banking versus habitat banking approaches, see BNG off-site: land banking vs habitat banking.

FAQ

Q: When exactly do the July 2026 BNG changes take effect?
The government has confirmed the changes will be introduced by the end of July 2026, subject to parliamentary scheduling. Developers with live applications should monitor GOV.UK guidance closely, as the precise commencement date affects which rules apply.

Q: Does removing the self-build exemption mean all self-build projects now need BNG?
Yes, unless the project footprint falls below 0.2 hectares under the new area-based exemption, or another exemption applies. Self-build schemes above 0.2 hectares will need to demonstrate 10% BNG from the point the change comes into force.

Q: Will the brownfield residential exemption (up to 2.5 ha) be confirmed before July 2026?
The consultation closed on 10 June 2026. No outcome had been confirmed as of the date of this article. Developers should not rely on this exemption until a formal government response is published.

Q: How does the hierarchy change for minor development affect planning applications in practice?
Under the revised hierarchy, small-site applicants no longer need to demonstrate that on-site delivery is impractical before proposing off-site units. This reduces the evidential burden and speeds up the pre-application ecology process for minor schemes.

Q: What legal mechanism secures BNG for a small site?
Either a Section 106 planning obligation or a conservation covenant must secure the habitat management and monitoring obligations for 30 years. The choice depends on whether the land is within the application site or on third-party land.

Q: Are NSIPs required to follow the same biodiversity gain hierarchy as other developments?
The mandatory BNG framework for NSIPs from 2 November 2026 follows the same general hierarchy (on-site, then off-site, then statutory credits), but the specific procedural requirements for NSIPs under the Planning Act 2008 differ from the Town and Country Planning Act route. NSIP applicants should seek specialist advice early in the development consent order process.

Conclusion

The Biodiversity Net Gain changes July 2026 small sites NSIPs reforms mark a clear shift in how England's BNG framework operates. The move to an area-based exemption at 0.2 hectares creates a more transparent threshold for small developments, while the removal of the self-build exemption closes a gap that was never intended to be a compliance route. The equal weighting of off-site gains in the minor development hierarchy reduces friction for small-site applicants and should speed up pre-application ecology work.

For ecologists and planning consultants, the immediate priorities are:

• Review all live small-site applications to confirm whether the self-build exemption has been relied upon and, if so, prepare a BNG compliance strategy.
• Advise NSIP clients to commission habitat baseline surveys now and begin off-site unit procurement ahead of November 2026.
• Monitor the brownfield residential consultation outcome and update client advice accordingly.
• Ensure all BNG plans, Section 106 agreements, and conservation covenants reflect the updated hierarchy rules once the July 2026 changes are confirmed.

For landowners, the NSIP mandate creates a genuine opportunity. Registering suitable land as a habitat bank before November 2026 positions it to meet anticipated demand from large infrastructure projects. For guidance on that process, contact Biodiversity Surveyors or explore the guidance for landowners.

The BNG framework is still maturing. Staying current with GOV.UK guidance, DEFRA publications, and professional body updates from the RTPI and CLA is not optional — it is a core part of competent practice in 2026.

References

• DEFRA, Biodiversity Net Gain: changes to the biodiversity gain hierarchy and exemptions, GOV.UK, 2026. https://www.gov.uk/government/consultations/biodiversity-net-gain-changes-to-the-biodiversity-gain-hierarchy-and-exemptions
• DEFRA Blog, Biodiversity Net Gain updates, April 2026. https://defraenvironment.blog.gov.uk
• GOV.UK, Biodiversity net gain, guidance hub. https://www.gov.uk/guidance/biodiversity-net-gain
• Bird & Bird, BNG for NSIPs: what developers need to know, 2025. https://www.twobirds.com
• Country Land and Business Association (CLA), Biodiversity Net Gain guidance for landowners, 2024. https://www.cla.org.uk
• Royal Town Planning Institute (RTPI), BNG and infrastructure: planning for the NSIP mandate, 2025. https://www.rtpi.org.uk
• Environment Act 2021, Schedule 14. https://www.legislation.gov.uk/ukpga/2021/30/schedule/14