Next step on BNG for NSIPs

This article was first published on Estates Gazette on 23 May 2026.

The government announced on 15 April 2026 that a 10% biodiversity net gain objective will apply to nationally significant infrastructure project applications made on or after 2 November 2026. It brings certainty, welcome clarifications of detail and, for projects that can be submitted on or before 30 October 2026, the possibility of reducing the costs and complexity of BNG delivery.

There are 60 English NSIP projects listed as being at pre-application stage on the Planning Inspectorate's database. Around 20 of them may be submitted before NSIPs are required to secure delivery of biodiversity value that exceeds the pre-development value of the on-site habitat by at least 10%. The further postponement of BNG for NSIPs, from the expected implementation of May to November 2026, offers these NSIP projects the opportunity to reduce ENG-related costs and complexity.

Avoiding BNG altogether is unlikely. This is because biodiversity enhancement is already a material consideration through national policy statements, the National Planning Policy Framework and development plans. NSIP applications reflect years of preparatory work and iterative project design development with comprehensive landscape and biodiversity mitigation plans already incorporating BNG. The need to deliver BNG will have been assumed in the negotiation of many of the legal agreements necessary to secure the project. So, some biodiversity gain will already be baked into most, if not all, emerging NSIPs.

For NSIPs preparing for 10% BNG, there are helpful clarifications in the response to last summer's consultation. From 2 November 2026, all development consent order applications must provide 10% BNG. This includes NSIPs and other projects subject to a direction from the secretary of state that development consent is required. Developments in the marine environment, below low-water mark, are not included (yet). Amendments to consented DCOs, or those applied for before 2 November 2026, will avoid the 10% BNG requirement.

Biodiversity metric

The statutory biodiversity metric will be used. Although there will be no differentiation between NSIP sectors and types, the metric for NSIPs will contain some differences from the metric used for the Town and Country Planning Act 1990. The 10% BNG requirement will apply only to habitats that will be impacted or used to deliver BNG. So, not all land within the application boundary. A BNG boundary plan must include all areas of habitat loss. The date for calculating the pre-development value will be the date of submission of the biodiversity gain plan, rather than submission of the DCO application, which means that updated biodiversity gain plans can be based on revised values. BNG for impacts on temporary land will not need to be secured for 30 years, if reinstated within five years, providing the habitats are of low or very low distinctiveness. This should incentivise choice of such habitat and efficient construction timescales. Either or both on-site and off-site BNG delivery will be acceptable from the outset, with statutory credits firmly a last resort.

Decision-making process

BNG for NSIPs will be subject to a two- or three-stage decision-making process:

1. An outline biodiversity gain plan will be submitted at application stage, with securing requirements proposed in the draft DCO, and considered as part of the NSIP application. The examining authority will confirm in its recommendation to the secretary of state if the 10% biodiversity gain objective is met.
2. After the DCO has been issued, an updated or phase biodiversity plan will be submitted to the discharging authority (the local planning authority or the secretary of state in consultation with local authorities) for approval prior to commencement of development.
3. If necessary for ongoing management, monitoring, reporting and appropriate enforcement, phase biodiversity gain plans or updated biodiversity gain plans may be submitted to calculate and secure any final shortfall in biodiversity units.

Applicants will be required to demonstrate how impacts on irreplaceable habitat have been avoided. Where enhancements to irreplaceable habitat on-site are proposed, and no compensation for loss of that habitat is required, such habitat and enhancements can be included within the BNG baseline and delivery. In addition to the requirement to secure and maintain significant on-site habitat for 30 years, there should be basic maintenance of habitats for the remaining lifespan of the NSIP. Where NSIP developers can provide excess BNG units, these can be registered and allocated as off-site gains for another development in line with requirements for biodiversity gain sites.

Final government actions

The statutory instrument implementing the provisions around biodiversity gain statements was laid before parliament on 5 May and came into force on 7 May 2026. A metric user guide with the updated detail for NSIPs and additional guidance will also need to be published before November 2026.

If your NSIP may be submitted before 2 November 2026, audit your scheme now and confirm what BNG proposals can realistically be de-scoped or simplified. If submission will fall after that date, ensure that delivery of BNG is calculated using the revised details and build in sufficient time to react to the forthcoming statutory instruments and guidance.