CIL, Section 106, BNG and nutrient neutrality

Four different requirements

CIL is an infrastructure levy. Section 106 secures planning obligations. Biodiversity Net Gain (BNG) measures habitat improvement. Nutrient neutrality addresses effects on particular protected sites. They need separate treatment in the site appraisal, even where a single legal agreement secures several commitments.

The proposal’s Chapter 11 discusses all four. Its expectations of relief must be tested against the actual tenure, land interest, planning permission and site. Charitable ownership, an affordable rent and a timber building system do not together establish a general exemption.

CIL: establish liability and secure any relief

The Community Infrastructure Levy is charged by authorities with a charging schedule, using the applicable rules, floorspace and rates. Qualifying development may receive charitable or social housing relief, but the detailed eligibility conditions matter. The proposal’s income-linked rent model must be checked against those conditions.

Relief requires the appropriate claim and evidence. Social housing relief must be granted before commencement; starting early can lose it. The delivery programme needs liability, relief and commencement procedures resolved before works trigger the charge. Changes in use or tenure can also affect retained relief.

Source: Government planning practice guidance: CIL, charitable relief and social housing relief.

Section 106: agree obligations that meet the tests

Section 106 of the Town and Country Planning Act 1990 enables legally binding planning obligations, normally attached to the land. These can secure affordable housing and measures needed to mitigate a development’s impacts.

An obligation relied on to grant permission must be necessary to make the development acceptable in planning terms, directly related to it, and fairly and reasonably related in scale and kind. Providing affordable homes does not automatically remove transport, education, open-space or other justified obligations. Viability needs evidence; the Trust’s proposed rent does not itself make every contribution unlawful.

For the pilot, heads of terms should identify each obligation, its trigger, who delivers it, its cost and any continuing duty. That record should distinguish the affordable-housing commitment from other infrastructure and mitigation requirements.

Source: Government planning practice guidance: planning obligations.

BNG: measure the habitat outcome

Biodiversity Net Gain requires at least a 10% increase in biodiversity value for development within its scope, using the statutory metric. This is not a requirement to make 10% of the site green. Habitat type, condition and other metric factors affect the calculation.

Check exemptions first. Current guidance says that, from 6 August 2026, development of 0.2 hectares or below is exempt. A larger housing scheme cannot assume exemption because the homes are affordable. Brownfield status also does not establish a low ecological baseline.

Where required, establish the baseline, design the habitat response and obtain approval of the gain plan before starting development. Delivery can involve onsite habitat, registered offsite units and, as a last resort, statutory credits, subject to the applicable rules. Significant onsite gains and offsite gains require management for at least 30 years. Budget for the legal arrangements, management and monitoring as well as initial works.

Source: Defra: understanding BNG, including the August 2026 changes.

Nutrient neutrality: check the catchment and wastewater route

In affected catchments, additional residential occupation can increase nitrogen or phosphorus reaching protected habitats through wastewater and land-use changes. Nutrient neutrality demonstrates that the development will not add to that pollution after mitigation. A low-carbon chassis does not resolve the wastewater impact.

The site appraisal needs the relevant catchment, wastewater treatment works, occupancy assumptions and nutrient budget. Natural England’s calculators account for existing and proposed land use, drainage and treatment upgrades. The result establishes any mitigation requirement in kilograms per year; it is not a uniform charge per home.

Source: Natural England: nutrient budgets and catchment calculators.

The Nature Restoration Fund offers a further route where an Environmental Delivery Plan is in force and covers the relevant impact. In those circumstances a developer may pay the nature restoration levy. Availability and coverage must be checked for the site; the fund does not replace BNG or remove obligations for impacts outside the plan.

Source: Government guidance: Nature Restoration Fund and Environmental Delivery Plans.

Carry the requirements into the delivery budget

Before committing a site, the pilot needs a schedule of confirmed charges, approved relief, planning obligations, ecological mitigation and continuing management. Identify which costs sit with the Trust, the landowner, the infrastructure provider or another party, and when each must be paid or delivered.

CIL relief does not provide roads, utilities or drainage. The proposal still depends on a funded infrastructure package, including its intended Homes England contribution. The funding section and pilot scheme set out that dependency.