Biodiversity Net Gain Changes for Developers from August 2026

Biodiversity Net Gain (BNG) has become a familiar part of the planning process for developers and local planning authorities (LPAs) since its introduction in 2024.

Under the Environment Act 2021, most planning applications submitted under the Town and Country Planning Act 1990 are required to demonstrate BNG of at least 10%. Essentially, it requires, with limited exceptions, development to leave the natural environment in a measurably better state than it was before the development took place.

If you would like to learn more about the fundamentals of BNG, you can read our previous article, What Is Biodiversity Net Gain and How to Achieve It?

From 6 August 2026, The Biodiversity Gain (Town and Country Planning) (Amendments and Transitional Provisions) (England) Regulations 2026 (the 2026 Regulations) introduce several important changes to the BNG regime. While the overall requirement to deliver biodiversity net gain remains unchanged, the amendments are intended to make the system more proportionate for smaller developments.

Key Takeaways

• The new BNG regulations came into force on 6 August 2026, introducing changes designed to simplify the process for smaller developments.
• The 10% Biodiversity Net Gain requirement remains unchanged for developments that are subject to BNG.
• Developers of non-major schemes now have greater flexibility, with on-site habitat creation and registered off-site biodiversity gains given equal preference.
• New exemptions apply to qualifying developments on sites of 0.2 hectares or less and certain temporary developments, provided specific conditions are met.
• The self-build and custom-build exemption has been removed, although some developments may now qualify under the new small sites exemption instead.
• The changes only apply to planning applications submitted on or after 6 August 2026, so it's important to check which rules apply before making an application.

Why Have the Rules Changed?

In the explanatory memorandum accompanying the 2026 Regulations, the Department for Environment, Food and Rural Affairs (DEFRA) explains that the BNG regime is generally achieving its objectives. However, evidence suggests that the administrative burden and compliance costs have been disproportionately challenging for some smaller developments.

The 2026 Regulations are therefore intended to reduce those burdens while maintaining the overall environmental benefits of BNG.

What Has Changed?

The 2026 Regulations introduce four key changes to the existing BNG framework.

1. Changes to the Biodiversity Gain Hierarchy

Under the previous regime, developers were expected to follow a strict hierarchy when securing biodiversity net gain.

The required approach was to:

• avoid adverse impacts on habitats wherever possible;
• where impacts could not be avoided, minimise and mitigate them by on-site enhancement;
• where providing enhancement was not possible, provide biodiversity gains through on-site habitat creation;
• where on-site gains were not achievable, secure registered off-site biodiversity creation; and
• only as a last resort, purchase statutory biodiversity credits.

For non-major development, the 2026 Regulations amend this hierarchy. Rather than requiring developers to prioritise on-site habitat creation over off-site solutions, on-site habitat enhancement and creation are now given the same level of preference as registered off-site biodiversity gains. Statutory biodiversity credits remain the option of last resort.

This change gives developers of smaller schemes greater flexibility where creating habitat on-site is impractical or constrained.

For these purposes, major development generally includes:

• developments of 10 or more dwellings;
• residential development on sites of 0.5 hectares or more where the number of dwellings is unknown;
• non-residential development providing 1,000 square metres or more of floorspace;
• development on sites of one hectare or more; and
• mineral and waste development.

2. New Exemption for Small Sites

A new exemption has been introduced for development on sites of 0.2 hectares or less, provided that the development does not affect any on-site priority habitat.

This exemption removes the need for qualifying developments to comply with the BNG requirements, reducing the regulatory burden for many smaller projects.

3. New Exemption for Temporary Development

The Regulations also introduce an exemption for certain temporary developments.

To qualify, the development must:

• consist entirely of temporary development;
• not affect any on-site priority habitat; and
• be removed, with the land reinstated, within five years.

The Regulations also prevent developers from relying on a succession of temporary planning permissions to avoid BNG requirements. Where consecutive temporary permissions would result in the same development remaining for more than five years, the exemption will not apply.

4. Removal of the Self-Build and Custom Build Exemption

The previous exemption for certain self-build and custom-build developments has been removed.

According to DEFRA, this exemption proved difficult to implement and enforce in practice. However, many developments that previously relied upon this exemption are now likely to qualify under the new exemption for small sites instead.

Who Do the Changes Affect?

The new rules do not apply retrospectively. The amended BNG regime applies only where the relevant planning application is submitted on or after 6 August 2026.

The 2026 Regulations also confirm that they do not apply to applications made under section 73 of the Town and Country Planning Act 1990 where the original planning permission was applied for or granted before 6 August 2026.

Do the new BNG rules apply to existing planning permissions?

No. The changes only apply to planning applications submitted on or after 6 August 2026. Existing applications continue under the previous rules, subject to the transitional provisions.

Is Biodiversity Net Gain still 10%?

Yes. The requirement to achieve at least 10% Biodiversity Net Gain has not changed.

Are self-build developments still exempt?

No. The self-build exemption has been removed. However, some smaller developments may qualify for the new small sites exemption.

What does this mean for the future?

Although the changes do not alter the overall principle that development should leave biodiversity in a better state than before, they do introduce greater flexibility and a number of targeted exemptions for smaller developments.

Developers, landowners and local planning authorities will need to consider carefully which version of the BNG regime applies to each application, particularly where transitional provisions apply.

Whether these reforms successfully reduce costs and administrative burdens for smaller developments without undermining the environmental objectives of BNG remains to be seen. As the new regime begins to operate in practice, it will be important to monitor how local planning authorities interpret and apply the changes.

Contact our legal experts