Biodiversity Net Gain: What Finance Teams Need to Know in 2026

Biodiversity Net Gain (BNG) became a mandatory requirement for most new developments in England from February 2024, and 2026 has brought a further round of significant changes to how it works. For finance and sustainability professionals, BNG is a useful case study in how environmental requirements increasingly carry direct, quantifiable financial implications rather than being a purely qualitative ESG consideration.

What Biodiversity Net Gain actually requires

BNG requires that habitats for wildlife affected by a development are left in a measurably better state than before construction began — not just avoiding harm, but delivering a quantified improvement. Developers must deliver a minimum 10% biodiversity net gain, calculated using a standardised biodiversity metric that accounts for habitat size, quality, type, and location, rather than a simple area-based calculation.

BNG applies broadly across major developments and most small sites, with nationally significant infrastructure projects brought into scope from November 2026. There is a size-based exemption: as of August 2026, developments of 0.2 hectares or below are exempt from the requirement.

The delivery hierarchy

Developers aren't free to simply buy their way to compliance. The framework requires a defined hierarchy: first, deliver the biodiversity gain on-site; if that's insufficient, combine on-site delivery with off-site biodiversity gains (typically through habitat creation on other land, or purchasing biodiversity units from a habitat bank); and only as a genuine last resort, purchase statutory biodiversity credits directly from the government. This ordering exists specifically to discourage developers from treating off-site credit purchases as a default, cheaper substitute for genuine on-site environmental improvement.

What changed in 2026

From 6 August 2026, small developments gained meaningful new flexibility: rather than being required to prioritise on-site delivery strictly before considering off-site options, they can now consider on-site and off-site delivery together, at the same time. This is a practical easing of the compliance burden specifically for smaller developers, for whom sequential on-site-first requirements had proven disproportionately difficult to satisfy. Separately, nationally significant infrastructure projects became subject to BNG requirements from 2 November 2026, under their own specific set of rules — bringing major infrastructure into a framework that had previously applied mainly to conventional property development.

How BNG interacts with land value and deal structuring

Because BNG costs scale with the biodiversity value lost and the delivery route chosen, the requirement has started to materially affect how land acquisition due diligence and development appraisals are run. A site with existing high-value habitat can carry a meaningfully larger BNG obligation than a similarly sized but ecologically degraded site, which means biodiversity assessment now needs to happen early in the acquisition process rather than as a late-stage planning formality — a gap in this analysis can turn what looked like a straightforward land deal into one with a significant, previously unbudgeted compliance cost once the biodiversity metric calculation is actually run.

Why this matters for finance and ESG professionals

BNG is a clear example of environmental compliance translating directly into a line-item cost that has to be budgeted, provisioned for, and factored into development appraisal and land valuation — not an abstract sustainability commitment sitting separately from financial planning. For any business involved in property development, land acquisition, or infrastructure — or advising clients who are — understanding how BNG costs are calculated, and where the hierarchy pushes cost toward on-site versus off-site versus statutory credits, is directly relevant to accurate financial modelling and risk assessment.

It's also a useful illustration of a broader ESG-reporting trend: environmental requirements that started as planning-law obligations are increasingly quantified, auditable, and tracked with the same rigor as financial metrics, using standardised measurement frameworks (the biodiversity metric, in this case) rather than qualitative narrative reporting alone — biodiversity units, once purchased or committed to a habitat bank, function similarly to a long-term financial obligation, with maintenance and monitoring commitments typically running for 30 years, which is a genuinely unusual liability horizon for most development finance to plan around.

Frequently asked questions

What is the minimum biodiversity gain developers must achieve?
A 10% net gain in biodiversity value, calculated using a standardised biodiversity metric that accounts for habitat size, quality, type, and location.

Are all developments subject to Biodiversity Net Gain?
Most major and small developments are covered, with nationally significant infrastructure projects added from November 2026. Developments of 0.2 hectares or below are exempt as of August 2026.

Can developers simply buy their way to compliance with biodiversity credits?
No — the framework requires a defined hierarchy prioritising on-site delivery first, with off-site gains and statutory credits available only when on-site delivery is genuinely insufficient (small developments gained more flexibility here from August 2026).

Understanding quantified environmental compliance frameworks like this is core to Learnsignal's CPD courses, and our Carbon Accounting and Scope 3 Emissions guide is a useful companion read on another area where environmental measurement is becoming as rigorous as financial reporting.