Planning application stuck on nutrient neutrality? Here is what the council needs

Published 25 September 2026 — reviewed against the regs as they stand.

Why the council can’t decide it yet

Some rivers, estuaries and wetlands in England are protected habitats that are already carrying more nitrogen or phosphorus than they can cope with. New homes add to that load — mostly through their waste water, which reaches the water after treatment — and Natural England has advised the planning authorities in 27 of these catchments that development there should be nutrient neutral: adding nothing, once mitigation is counted.

The advice matters because of the Conservation of Habitats and Species Regulations 2017. Where a development is likely to have a significant effect on a protected site, the planning authority must carry out an appropriate assessment, consulting Natural England, and may grant permission only once it has ascertained that the development will not adversely affect the site’s integrity. More nutrients reaching a site that is already failing is a significant effect. Until the council has evidence that your scheme’s load is zero, or mitigated to zero, it cannot reach that conclusion — and the application waits.

That is why a scheme with everything else agreed can sit undetermined for months. It is a legal test, not a local policy, and there is no discretion to waive it.

Is your scheme caught?

Two questions settle it.

Where does it drain? The catchment is decided by where the site’s water ends up, and foul and surface water can go different ways — a site outside a catchment on the map can still be in it through the treatment works its sewage goes to. The catchment map shows all 27, coloured by the nutrient that applies, and our permit register has the consented concentrations for 675 treatment works across 22 of them.

Does it add overnight stays? New dwellings, conversions, houses in multiple occupation, holiday lets, care homes, student accommodation, hotels and campsites all do. The trigger is a net increase, so an extension to an existing home is generally not caught unless it creates a separate dwelling. Natural England’s advice also applies at reserved matters and to prior approval applications, so an outline consent does not get a scheme past it. Non-residential development is caught where it adds waste water — a new commercial kitchen, for instance.

What the council needs

1. A nutrient budget. The kilograms of nitrogen or phosphorus a year the scheme adds, worked through Natural England’s methodology and the calculator for the catchment. The waste water term comes from the number of dwellings, an occupancy rate (2.4 people per dwelling by default), daily water use (usually the 110 litres per person a day optional standard, plus Natural England’s 10-litre allowance) and the permitted discharge concentration at the treatment works — or the performance of a private treatment plant. The change in land use is added, any sustainable drainage designed to remove nutrients is credited, and the net figure is multiplied by 1.2, Natural England’s 20% precautionary buffer. The nutrient neutrality assessment page goes through each stage.

2. A mitigation proposal. If the budget is above zero, how you will bring it to zero: nutrient credits from a scheme in the same catchment, measures on your own land, or a treatment plant that removes more than the works would. One credit is normally one kilogram a year, secured in perpetuity.

3. Evidence that the mitigation is secured. Not a promise — a credit certificate or allocation, a legal agreement, or a condition the council is satisfied can be met. Some councils also want the budget wrapped in a short statement to inform their Habitats Regulations Assessment: the same facts, set out for the ecologist.

What the ecologist checks

The council’s ecologist is not re-deriving the methodology; they are checking you applied it to the right facts:

• The right catchment and the right nutrient. Some catchments are nitrogen, some phosphorus, a few both — and the wrong nutrient is the commonest mistake in a do-it-yourself submission.
• The right treatment works and permit, including whether the permit tightens in 2030.
• Occupancy and water use. A lower figure than the defaults needs a reason, such as a water efficiency condition or one-bedroom flats the authority accepts a lower occupancy for.
• The current land use, with evidence where it matters. A greenfield site on fertilised arable land can come out with a large negative land-use term; the authority will want to see that the land really was farmed that way.
• The buffer, applied once and to the net figure.
• The current version of the calculator. Natural England’s own credit scheme rejects applications worked on an out-of-date one.

Securing the mitigation

Credits are the usual route for small schemes. Each catchment has its own providers, and prices vary enormously; the nutrient credits calculator turns a budget into the number of credits and, where a scheme publishes a price, the likely cost.

How they are secured depends on the scheme. Natural England’s own scheme — currently selling credits in Poole Harbour and the Tees — asks for your planning application reference before it allocates credits, gives you a provisional certificate for the council once a deposit is paid, and takes the balance after permission, when a final certificate goes to the council to show the condition has been met. Other providers sell outright, or the council ties the purchase into a section 106 agreement. Schemes of ten to 49 homes may soon use national section 106 templates. Whatever the mechanism, the council has to be able to rely on it before it decides.

The 2030 split. Where the treatment works has a permit that tightens on 1 April 2030 under the Levelling-up and Regeneration Act 2023, the council can take the upgrade as certain. The budget then has two figures, and the permanent mitigation need only cover the lower, post-2030 one; the difference until 2030 can be covered with cheaper temporary credits where a scheme sells them.

On-site measures suit larger sites: taking fertilised land out of production within the red line, a wetland, or sustainable drainage designed and evidenced for nutrient removal. They need to be secured for as long as the development’s effect lasts, which in practice means a legal agreement.

The levy route

The Planning and Infrastructure Act 2025 created a second route. Natural England can make an Environmental Delivery Plan for a catchment, and a developer can then pay a nature restoration levy instead of finding its own mitigation. The process is set out in the levy rulebook: request to use the plan, receive a commitment certificate, submit it with the planning application, and pay before work starts.

The Nature Restoration Levy Regulations 2026 have been in force since 11 September 2026. The first plan — the draft Norfolk Environmental Delivery Plan, covering the River Wensum and the Bure and Yare Broads catchments at a proposed £2,675 per home — went out to consultation on 17 September 2026 and is not in force. Until a plan is in force for your catchment, and your site is inside it, the budget and the mitigation are still the only route.

When to do what

Before you submit. Run the budget as soon as the number of dwellings and the drainage route are known — it can change the scheme, and some councils’ validation lists already ask for it in the affected catchments. Line up the mitigation at the same time: credit schemes have limited capacity, and some will not allocate until the application has a reference.

While it is being decided. Expect questions on the land use, the occupancy and the treatment works. Answering with evidence rather than argument is what keeps it to weeks rather than months.

After permission. Complete the credit purchase or discharge the condition before the trigger it sets — usually before work starts or before anyone moves in.

What it costs

• The assessment. Consultants’ nutrient assessments routinely run into the hundreds of pounds for a small scheme. NutrientMonkey works the budget out free on screen; the planning-ready report is £79 + VAT (£94.80 inc VAT).
• The mitigation. Published credit prices run from about £1,800–£3,300 per kilogram of nitrogen a year in Poole Harbour, the Tees, Stodmarsh and the Solent to £28,000 per kilogram of phosphorus in Cumbria and as much as £82,000 in the Broads and the Wensum. Where no price is published, providers quote.

The budget is also the place to save money. The default occupancy and water use are conservative for small flats and for schemes with a 110-litre condition, a fertilised greenfield site earns a negative land-use term, and a better treatment plant cuts the waste water load directly. Each kilogram argued away is a credit you do not buy.

Do the budget yourself, free

NutrientMonkey runs Natural England’s methodology for all 27 catchments in your browser: pick the catchment and the nutrient locks itself, enter the dwellings, the drainage route and the treatment works, add the land use and any sustainable drainage, and the budget updates as you type — with the pre- and post-2030 figures where a permit tightens. It is free to use; the planning-ready report, with every line of the arithmetic and a report ID the ecologist can verify online, is £79 + VAT. See an example report (PDF) first. Your figures should reproduce in Natural England’s own calculator for the catchment, which remains the reference.

What you’ll need to hand: the site address and its area; the number and type of dwellings; where the foul drainage goes — the treatment works, or a private plant; the current use of the land; and any surface water proposals.

Where the case is harder than the calculator — a private treatment plant, a phased scheme across the 2030 change, a land-use history the authority may dispute, or an authority that wants a consultant’s signed assessment — our nutrient neutrality assessment service prepares it.