Nutrient Neutrality Explained: Catchments, Budgets and the Nature Restoration Fund

In 74 local planning authorities, a scheme that adds wastewater to an already overloaded catchment cannot be permitted until the extra nitrogen and phosphorus are cancelled out. The regime that replaces it is being built right now, and the first draft plan went out for consultation in September 2026.

What nutrient neutrality actually requires

Nutrient neutrality requires that a development adds no net nitrogen or phosphorus load to a protected habitat site that is already in unfavourable condition because of nutrient pollution. Whatever extra load the scheme generates — overwhelmingly through wastewater from the people who will live or work in it — has to be cancelled out, so the net effect on the catchment is zero or better.

It is a harder constraint than most environmental planning requirements, for a structural reason. It is not a policy target that can be weighed against housing need in a planning balance. It is a consequence of the Habitats Regulations, which require an appropriate assessment where a development could have a significant effect on a protected site, and which prevent permission being granted unless the authority can positively conclude there will be no adverse effect on the integrity of that site. Where the site is already failing because of nutrients, an authority cannot reach that conclusion about a scheme that adds more of them. The application does not get refused on balance — it stalls, sometimes for years, until the nutrients are dealt with.

That is why nutrient neutrality has held up tens of thousands of homes in affected catchments since Natural England began issuing its advice, and why it generates far more heat than its relatively narrow geographic footprint would suggest.

Where it applies

Natural England's nutrient advice, issued in 2019 and extended in 2022, covers 74 local planning authorities, for 31 protected sites spanning 27 river catchments assessed as being in unfavourable condition because of nutrient pollution.

The best-known affected areas include:

• The Solent — the original and most heavily affected catchment, covering much of south Hampshire
• The Somerset Levels and Moors
• Stodmarsh in Kent
• Poole Harbour in Dorset
• The River Avon
• The River Lugg in Herefordshire
• The Broads in Norfolk and Suffolk

The affected list is specific and published, and the only reliable way to establish whether a site is caught is to check the current Natural England advice for the catchment and confirm the position with the local planning authority. Catchment boundaries do not follow administrative ones, so neighbouring sites in the same district can fall on opposite sides of the line.

Being outside a nutrient catchment is not the same as being unconstrained. Several of the same authorities also operate water neutrality requirements, which address water quantity rather than nutrient load. They are separate tests with separate calculations, and a site can be subject to both.

How a nutrient budget works

A nutrient budget is an arithmetic exercise with a precautionary thumb on the scale. The components:

1. Additional load from the development. Driven by the number of new occupants, their estimated wastewater generation, and the nitrogen and phosphorus concentrations in the discharge from the treatment works that will serve the site. A scheme served by a works with poor nutrient removal starts from a worse position than an identical scheme served by a modern one.
2. Existing load from the current land use. Netted off. This is why arable land — which already leaches substantial nitrogen through fertiliser application — can produce a lower net budget than a greenfield pasture site, and why previously developed land in the catchment is attractive.
3. The calculator's assumptions. Natural England publishes catchment-specific calculators that set occupancy rates, an assumed development lifetime and a precautionary buffer. Those assumptions are not negotiable inputs; using your own occupancy figures is a reliable way to have a budget rejected.

The output is a required mitigation quantity, usually expressed in kilogrammes of nitrogen or phosphorus per year, which has to be delivered for the lifetime of the development.

What counts as mitigation

Four broad routes, in rough order of how often they are used:

• Buying nutrient credits. Mitigation schemes — run by local authorities, Natural England, water companies and private operators — create nutrient reductions and sell them as credits. This is the dominant route for small and medium schemes, because arranging your own mitigation is disproportionate below a certain size. Natural England runs its own Nutrient Mitigation Scheme, and clarified its role in that scheme in May 2026.
• Land use change. Taking arable land out of production, reverting it to permanent grassland or woodland, and securing it long-term. The nutrient saving is the difference between the fertilised and unfertilised states.
• Constructed wetlands and interception. Engineered treatment that removes nutrients from water before it reaches the protected site.
• On-site or upgraded wastewater treatment. Package treatment plants achieving very low nutrient concentrations, or contributions to upgrading the receiving works.

Whichever route, mitigation has to be additional — it cannot be something that was going to happen anyway, such as a legislated upgrade to a wastewater treatment works already required in the catchment — and it has to be secured for the development's lifetime, normally through a section 106 agreement or conservation covenant. An intention to mitigate is not mitigation.

What is changing: Environmental Delivery Plans

The project-by-project model has always been inefficient. Every developer in a catchment separately commissions ecological advice, separately sources mitigation and separately negotiates a legal agreement, to address a problem that is identical across the whole catchment.

Part 3 of the Planning and Infrastructure Act 2025, which received Royal Assent on 18 December 2025, replaces that with a strategic mechanism:

• Natural England prepares an Environmental Delivery Plan (EDP) for an area, identifying the conservation measures needed to address a specific environmental impact across the whole of it.
• Developers discharge their obligation by paying a Nature Restoration Levy into the Nature Restoration Fund, rather than arranging their own mitigation.
• The EDP regime covers a defined list of impacts: nutrient neutrality, water quality, water resources and air quality. It is not a general-purpose replacement for environmental assessment.

The timetable is live but incomplete. Natural England notified the government in December 2025 that it intended to prepare 23 EDPs, 16 of them for nutrient pollution. The first draft EDP went out for consultation on 17 September 2026, covering the Norfolk Broads and the River Wensum, and it has not been uncontroversial — the ecological community's central objection is that paying into a fund severs the link between a specific impact and a specific, demonstrated remedy.

What this means for a site today

The single most important point, and the one most often got wrong in commentary: nutrient neutrality has not been abolished, suspended or softened. Until an EDP is actually in place for a given catchment and covers the relevant impact, the existing requirements apply in full, unchanged.

So for a scheme being brought forward now:

• Assume the existing regime. Budget for a nutrient assessment and mitigation, on the current rules, in the current way.
• Do not programme around a future EDP. One draft plan is consulting out of 16 intended for nutrients. A consultation opening is a long way from an EDP being made and operative.
• Start mitigation sourcing early. Credit availability in the tighter catchments is the binding constraint, not the calculation. Schemes stall waiting for credits, not waiting for arithmetic.
• Watch the catchment, not the Act. The question that determines your position is whether an EDP covers your catchment and your impact, not what stage the national programme has reached.

Common mistakes

• Reading Royal Assent as deregulation. The Act created a mechanism; the mechanism is being built catchment by catchment. Nothing changed for most sites on 18 December 2025.
• Using your own occupancy assumptions. The catchment calculator's assumptions are the ones that count, and substituting more favourable figures invites rejection.
• Claiming credit for mitigation that was happening anyway. Additionality is tested. Legislated treatment works upgrades in the catchment are generally not available to you as mitigation.
• Leaving credit purchase to the end. Availability, not price, is usually what delays schemes in the constrained catchments.
• Assuming nutrient neutrality and water neutrality are the same test. One is about nutrient load, the other about water quantity. Both can apply to one site, and each needs its own case.
• Treating the budget as a one-off design-stage number. Occupancy and discharge assumptions need to still be true at completion, and some authorities now look for confirmation that they are.

How this connects to your wider environmental reporting

Nutrient neutrality, water neutrality and Biodiversity Net Gain are three separate regimes that share one structure: establish a baseline, calculate what the development adds, close the gap through a defined hierarchy, and keep it secured for decades. They are also increasingly landing on the same desk, assessed by the same authority, against the same site.

What they have in common practically is that each case is only as strong as the measured data behind it — discharge volumes, consumption figures and the monitoring that shows design assumptions survived contact with the completed building. That is the same evidence that supports your trade effluent consents and BREEAM water credits, and it is what VerdCore's construction water tracking software is built to capture continuously rather than reconstruct.