0.2 Hectare BNG Exemption Small Sites August 2026: What UK Developers Need to Know

Last updated: August 29, 2026

Quick Answer: From 6 August 2026, planning applications for developments on sites of 0.2 hectares or less are exempt from mandatory Biodiversity Net Gain (BNG) under the Biodiversity Gain (Town and Country Planning etc) (Amendment) Regulations 2026, provided no on-site priority habitat is present or adversely affected. The 0.2 hectare BNG exemption for small sites from August 2026 is the most significant change for UK developers working on minor schemes, infill plots, and back-land developments since BNG became mandatory in 2024.

Key Takeaways

• The 0.2 ha exemption applies to applications submitted on or after 6 August 2026 only, it does not apply retrospectively to applications already in the system.
• The threshold is 0.2 hectares (2,000 m², roughly 40 m x 50 m, or about one-third of a football pitch) measured against the total planning red-line boundary, not just the built footprint.
• The exemption is conditional: if any Section 41 priority habitat is present on site and would be adversely affected, mandatory BNG still applies regardless of site size.
• The separate self and custom build exemption has been removed, but most self-build plots fall below 0.2 ha and are therefore covered by the new area-based threshold.
• Government analysis estimates that more than 50% of the smallest planning applications currently delivering mandatory BNG will be removed from the requirement by this change. [3]
• Developers must still provide evidence to support the exemption claim: an accurate red-line boundary, a site area calculation, and credible habitat survey evidence confirming no priority habitat is present.
• The de minimis exemption (less than 25 m² of habitat or 5 m of hedgerow affected) remains separate and distinct from the new area-based rule. [10]
• Even where BNG is exempt, other ecological obligations (protected species surveys, for example) may still apply.

What Is the 0.2 Hectare BNG Exemption for Small Sites?

The 0.2 hectare BNG exemption for small sites is a statutory area-based exemption from mandatory Biodiversity Net Gain, introduced by the Biodiversity Gain (Town and Country Planning etc) (Amendment) Regulations 2026. It means that planning applications where the total site area within the red-line boundary is 0.2 hectares or below do not need to comply with the 10% mandatory BNG requirement under the Environment Act 2021, as long as no on-site priority habitat is present and adversely affected. [1]

This exemption applies to both residential and non-residential development types. It is not limited to housing or to schemes previously categorised as "small sites" for the purposes of the Small Sites Metric. The single qualifying test is total site area, measured at the red-line boundary. [1] [7]

To put the size in context: 0.2 ha equals 2,000 m², which is approximately a 40 m x 50 m plot. Many urban infill plots, back-land gardens, single-dwelling self-build sites, and small commercial conversions fall comfortably within this threshold. [7] [10]

When Does the 0.2 Hectare BNG Exemption Start, August 2026?

The exemption came into force on 6 August 2026 and applies only to planning applications submitted on or after that date. [9]

Applications submitted before 6 August 2026, including those submitted after BNG became mandatory for minor sites (2 April 2024) but before the new regulations took effect, do not benefit from the new threshold. Those applications remain subject to the rules in place at the time of submission. Developers who submitted minor applications before 6 August 2026 and are still awaiting determination should seek specific advice, as the exemption will not apply automatically to their scheme. [9]

Which Developments Qualify for the 0.2 Hectare BNG Exemption?

A development qualifies for the 0.2 ha BNG exemption if two conditions are both met:

1. The total planning red-line site area is 0.2 hectares or less. This is the whole application site boundary, not just the area being built on, the garden, or the habitat impact footprint. [1] [7]
2. No on-site priority habitat is present and adversely affected. Priority habitats are those listed under Section 41 of the Natural Environment and Rural Communities Act 2006. Examples include traditional orchards, lowland mixed deciduous woodland, and lowland meadows. If any such habitat is present and the development would adversely affect it, the exemption does not apply. [1] [7]

The exemption covers residential and non-residential applications alike. There is no minimum dwelling number or use-class restriction, the test is purely area-based. [1]

Common mistake: Some developers measure only the built footprint or the garden area rather than the full red-line boundary. The exemption test uses the entire application site. Drawing the red line too tightly to manufacture a sub-0.2 ha area is likely to attract scrutiny from local planning authorities. [7] [10]

What Is the Difference Between the Old 0.1 Ha and New 0.2 Ha BNG Thresholds?

Before 6 August 2026, there was no general area-based exemption threshold for minor sites. Minor residential developments (fewer than 10 dwellings or under 0.5 ha for housing; under 1,000 m² floor space or under 1 ha for non-residential) became subject to mandatory BNG from 2 April 2024. The only area-related relief available was the de minimis exemption (less than 25 m² of non-priority habitat or 5 m of hedgerow affected) or the self and custom build exemption. [1] [10]

The 0.2 ha threshold introduced in August 2026 is a new, standalone exemption category. It does not replace de minimis; both can apply independently. The key distinction is that de minimis is based on the scale of habitat impact, while the 0.2 ha rule is based on total site area, regardless of how much habitat is affected. [10]

The comparison table below sets out the full picture.

Old Rules vs New Rules from 6 August 2026

Rule	Before 6 August 2026	From 6 August 2026
Minor site area threshold	No general area-based exemption	Sites of 0.2 ha or less are exempt (subject to no priority habitat condition)
Self and custom build exemption	Separate statutory exemption available	Removed; most schemes absorbed by 0.2 ha threshold
Temporary development exemption	Exempt if development is temporary	Remains exempt (unchanged in scope)
BNG hierarchy priority for minor sites	On-site first, then off-site, then statutory credits	Unchanged for sites still in scope; sites under 0.2 ha no longer need a Biodiversity Gain Plan

Do I Need to Pay BNG Credits for Sites Under 0.2 Hectares?

No, if your site qualifies for the 0.2 ha exemption, you do not need to purchase statutory biodiversity credits, commission a metric calculation, or submit a Biodiversity Gain Plan. The mandatory BNG requirement simply does not apply. [1] [6]

This is a meaningful cost saving. Statutory biodiversity credits are priced to reflect the cost of habitat creation, and off-site BNG delivery or credit purchases can add significant cost to small schemes. Government analysis indicated that BNG compliance was disproportionately burdensome on the smallest applications, which is precisely why this exemption was introduced. [3]

For further context on how biodiversity credits work for schemes that remain in scope, see this guide to biodiversity credits for developers.

How Much Will the BNG Exemption Save Small Developers?

Government's consultation response estimated that more than 50% of the smallest planning applications currently delivering mandatory BNG would be removed from the requirement by the 0.2 ha threshold. [3] Industry analysis has suggested that around half of all residential planning applications in England may now be exempt because they sit on sites of 0.2 ha or less with no priority habitat. [7]

The direct saving varies by site and location, but eliminating the need for a metric calculation, ecological report for BNG purposes, Biodiversity Gain Plan, and any off-site credit or habitat bank purchase can realistically save smaller developers several thousand pounds per application, as well as reducing pre-application timelines.

For developers whose sites remain in scope, understanding BNG for small development projects remains essential.

How Do I Check Whether My Site Has Priority Habitat?

Checking for priority habitat is the critical second condition of the exemption. A site under 0.2 ha that contains Section 41 priority habitat remains fully subject to mandatory BNG if that habitat would be adversely affected. [1] [7]

Practical steps to check:

• Natural England's Magic Map: The MAGIC mapping tool (magic.defra.gov.uk) shows recorded priority habitat distributions across England. This is the standard first-pass desktop check.
• Phase 1 Habitat Survey: A walkover survey by a qualified ecologist identifies habitat types on site and confirms whether any qualify as Section 41 priority habitats. This is the most reliable method and the one most likely to satisfy a local planning authority if the exemption is challenged. [7]
• Local planning authority pre-application advice: Some LPAs have local habitat data that supplements national datasets. Pre-application engagement can clarify expectations before submission.
• Historic Ordnance Survey maps and aerial photography: Useful for identifying features such as ancient hedgerows or orchards that may not appear on national datasets.

Developers should keep a clear record of the checks carried out, including the date of the survey, the surveyor's qualifications, and the conclusion reached. If a local authority disputes the exemption claim, this evidence trail is the first line of defence. [7]

For a detailed walkthrough of the survey process, see this guide on how to conduct a biodiversity impact assessment.

What About the Self and Custom Build Exemption?

The separate self and custom build exemption has been removed by the Biodiversity Gain (Town and Country Planning etc) (Amendment) Regulations 2026 with effect from 6 August 2026. [2] [9]

In practice, this removal has limited impact for most self-builders. The overwhelming majority of self-build and custom build plots are single-dwelling sites well below 0.2 ha in total area. Those schemes will now rely on the new area-based threshold rather than the dedicated self-build exemption, and the outcome is the same: no mandatory BNG applies. [7]

The small number of self-build or custom build schemes on sites above 0.2 ha, or those involving priority habitat, will need to comply with mandatory BNG in the same way as any other development of that scale. The removal of the dedicated exemption means there is no longer a separate route to exemption based solely on the self-build nature of the scheme.

Practical Steps for UK Developers Submitting Applications from 6 August 2026

The 0.2 hectare BNG exemption for small sites from August 2026 is straightforward in principle but requires careful preparation before submission. Follow these steps:

1. Calculate the total red-line site area accurately. Use a scaled site plan and confirm the figure in hectares. If the site is close to 0.2 ha, commission a precise land survey.
2. Commission a Phase 1 habitat survey. This confirms whether any Section 41 priority habitats are present and whether they would be adversely affected. Keep the surveyor's report with the application file. [7]
3. Cross-check against MAGIC mapping. Run the site through Natural England's MAGIC tool as a desktop baseline before the walkover survey.
4. Confirm the application date. The exemption applies only to applications submitted on or after 6 August 2026. If an application was already submitted before that date, the new threshold does not apply.
5. State the exemption clearly in the application. On the Planning Portal biodiversity net gain form, select the appropriate exemption category. DEFRA guidance lists "development no larger than 0.2 hectares (applies from 6 August 2026)" as a named exempt category. [1]
6. Retain all supporting evidence. Keep site area calculations, survey reports, MAGIC screenshots, and any pre-application correspondence in case the exemption is challenged during determination.
7. Check for other ecological obligations. BNG exemption does not remove the need for protected species surveys, ecological impact assessments, or other consents where they are triggered independently.

For broader guidance on planning your approach, see the guidance for developers resource and the overview of exempt projects.

Will the 0.2 Hectare Exemption Apply to All UK Regions?

The 0.2 ha exemption applies in England only. Mandatory BNG under the Environment Act 2021 is an England-specific regime. Wales, Scotland, and Northern Ireland have separate planning and biodiversity frameworks and are not affected by these regulations. [6]

Within England, the exemption applies uniformly, there is no regional variation. However, local planning authorities retain discretion to request ecological information in support of the exemption claim, and some LPAs with sensitive ecological areas may apply greater scrutiny to priority habitat checks than others. [7]

FAQ

Q: Does the 0.2 ha exemption apply to applications already submitted before 6 August 2026?
No. The exemption applies only to planning applications submitted on or after 6 August 2026. Applications already in the system before that date are assessed under the rules in place at the time of submission. [9]

Q: Is the 0.2 ha measured from the built footprint or the whole site?
The whole planning red-line site boundary. The test uses the total application site area, not just the area being built on, the garden, or the habitat impact zone. [1] [7]

Q: What happens if my site is just over 0.2 hectares?
If the site exceeds 0.2 ha, the exemption does not apply and mandatory BNG requirements must be met in full. Artificially tightening the red-line boundary to bring a site below 0.2 ha is likely to be challenged by the local planning authority. [10]

Q: Can I still rely on the de minimis exemption if my site is over 0.2 ha?
Yes, if less than 25 m² of non-priority habitat or 5 m of hedgerow would be affected. The de minimis and 0.2 ha exemptions are separate and can each apply independently, but neither applies where priority habitat is adversely affected. [10]

Q: Do I need any formal documentation to claim the exemption?
There is no separate application form, but you must select the correct exemption category on the Planning Portal BNG form and retain supporting evidence, specifically, an accurate site area calculation and a habitat survey confirming no priority habitat is present or adversely affected. [1] [7]

Q: Does the exemption apply to permitted development rights (PDR)?
Mandatory BNG under the Environment Act 2021 applies to planning applications, not to development carried out under permitted development rights. PDR schemes are already outside the mandatory BNG regime on a separate basis. [6]

Conclusion

The 0.2 hectare BNG exemption for small sites from August 2026 is a genuine and significant relief for UK developers working on minor schemes. For the first time, there is a clear, area-based rule that removes the majority of the smallest planning applications from mandatory BNG entirely, without the need for a metric calculation, Biodiversity Gain Plan, or credit purchase.

The practical implications are clear. If your site is 0.2 ha or less and contains no Section 41 priority habitat, you are exempt from mandatory BNG for applications submitted from 6 August 2026 onward. The steps to rely on that exemption are straightforward: measure the red-line area accurately, commission a Phase 1 habitat survey, cross-check MAGIC mapping, and record your evidence before submitting.

The two conditions that can catch developers out are an inaccurate red-line boundary and an undetected area of priority habitat. Both are avoidable with proper pre-application preparation. Investing in a competent ecological walkover survey before submission is far less costly than a BNG compliance requirement discovered mid-determination.

For sites that remain in scope, either because they exceed 0.2 ha or because priority habitat is present, the biodiversity gain hierarchy and the choice between on-site and off-site delivery remain important decisions. See the guide to biodiversity net gain off-site or on-site delivery for a detailed comparison of those options.

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