Off-site units and the registration of gain sites
Units only count once the land is registered, secured for 30 years and allocated to your application. The sequence, the costs and where deals come apart.
Off site biodiversity units registration is the step that turns a commercial agreement into something a local planning authority can accept. Units bought from a landowner do not count towards the biodiversity gain condition until the land is entered on the biodiversity gain sites register, the habitat is secured for at least 30 years by a conservation covenant or a planning obligation, and the units are formally allocated to your development on that register.
For a developer, the sequence matters more than the price. An unregistered unit is a promise, and a biodiversity gain plan cannot be approved on a promise.
When off-site units become necessary
The regime under Schedule 7A to the Town and Country Planning Act 1990, inserted by the Environment Act 2021, sets a hierarchy. Deliver the 10 per cent gain on site where you can, then off site on registered land, then buy statutory biodiversity credits from government as a last resort.
Off site becomes the answer in three situations. The site is too tightly developed to create habitat of the distinctiveness required. The trading rules block an on-site solution, because losses of medium or higher distinctiveness habitat have to be replaced like for like in the same broad habitat type and the site cannot accommodate it. Or the on-site creation would depend on land the scheme needs for something else.
Work out which of those applies before you go shopping, because it determines the habitat type you need to buy rather than just the number of units. Exemptions are a different question, and the grounds set out in the note on biodiversity net gain exemptions are worth confirming before any purchase.
What the gain sites register records
The register is operated by Natural England. An entry records the land by plan and title, the habitat present before enhancement and the habitat to be created or enhanced, the biodiversity value gained in units calculated with the statutory metric, the responsible person, the legal mechanism securing the land, the habitat management and monitoring plan, and the allocations made to specific developments.
Allocation is the part developers underestimate. Units sit on the register unallocated until the landowner allocates them to a named development, identified by its planning application reference. Once allocated they cannot be allocated again, which is the mechanism that prevents the same hectare being sold twice.
Registration and allocation attract fees payable to Natural England, set in regulations and revised from time to time, so check the current schedule rather than a figure from an earlier appraisal.
Before any of this, the development's own baseline has to be right. A Biodiversity Net Gain Assessment built on a habitat survey of the correct season, following the approach described in the note on significance of effects in an ecological impact assessment, is what sets the number of units you are buying. The statutory metric has to be completed by a competent person, and an AI-assisted draft is a starting point for that professional rather than a substitute.
Securing the land legally
Two mechanisms are available, and the choice affects the programme.
A conservation covenant under Part 7 of the Environment Act 2021 is an agreement between the landowner and a designated responsible body. It binds successors in title and runs for the agreed term. The responsible body has to be one Defra has designated, and it charges for entering into and monitoring the covenant.
A planning obligation under section 106 of the Town and Country Planning Act 1990 is the alternative. It requires the local planning authority for the area where the gain site sits to be a party, which is often not the authority determining your application. Two authorities, two legal teams and two sets of costs make this route slower on cross-boundary deals, though some authorities prefer it because they already hold the monitoring role.
Either way the agreement has to secure habitat creation and management for at least 30 years, with a management and monitoring plan, a monitoring regime, and remedies if the habitat fails to reach target condition. Read the remedies clause carefully. A covenant that imposes no consequence for failure transfers the risk to the developer whose units depend on it.
Spatial risk and where the units sit
The metric discounts off-site units according to how far they are from the development. Units in the same local planning authority area or National Character Area carry no spatial reduction, units in a neighbouring area are discounted, and units further afield are discounted more heavily.
The practical effect is that a distant unit costs more than its headline price, because you have to buy more units to deliver the same net gain. The mechanics are set out in the note on spatial risk multipliers in the biodiversity metric, and they should be applied before comparing offers rather than afterwards.
Strategic significance is the related lever. Habitat created in a location identified in a local nature recovery strategy or equivalent local plan mapping scores higher. Ask a prospective seller whether their site sits within that mapping, and ask for the evidence.
| Factor | Effect on the units you need to buy |
|---|---|
| Same authority area or National Character Area | No spatial reduction applied |
| Neighbouring area | Discount applied, so more units needed |
| Distant location | Larger discount, materially more units needed |
| Within local nature recovery mapping | Higher strategic significance, fewer units needed |
Buying units against creating them
Buying is faster and transfers delivery risk to the seller. Creating your own gain site on land you already control keeps the margin and the spatial advantage, at the cost of a 30-year management liability and the administrative work of registration.
The honest comparison is on three things. The cost of units including the spatial discount, the legal and registration cost, and the risk position. A purchase from an established habitat bank with the covenant already in place and units already on the register is a different product from an agreement with a farmer who intends to register next year.
For land you control, remember that the gain site cannot be land you are relying on for the on-site baseline, and that agricultural tenancies, grazing agreements and existing agri-environment scheme payments all need checking before the land is committed. A Preliminary Ecological Appraisal of the proposed gain site is the starting point for the baseline, and the survey season constrains when that can happen.
Timing against gain plan approval
The biodiversity gain condition is deemed to be attached to most planning permissions, and development cannot lawfully begin until the local planning authority has approved the biodiversity gain plan. That plan has to show how the 10 per cent is delivered, including the off-site units and their allocation.
So the critical path runs: habitat survey in season, metric calculation, decision on the off-site requirement, contract with the gain site provider, covenant or obligation completed, registration by the provider, allocation to your application reference, gain plan submitted, gain plan approved, start on site.
Registration and allocation are not instantaneous, and a provider who has not completed the covenant cannot allocate. Build in time, and make contractual payment milestones depend on allocation being evidenced on the register rather than on a promise to register.
Where the off-site market goes wrong
Six risks recur, and all of them are manageable with the right questions at heads of terms.
The provider is not yet registered and the timetable slips past your start date. The units on offer are the wrong habitat type for your losses under the trading rules. The spatial discount was not applied, so the deal delivers fewer units than it appeared to. The same units have been offered to more than one buyer, which the register prevents at allocation but not at negotiation. The management plan is thin and the authority queries whether target condition is achievable. And the price of statutory credits, which sets the ceiling on the market, moves in a way the appraisal did not anticipate.
Ask for the register entry number, the executed covenant or obligation, the management and monitoring plan, the metric output showing the units claimed, and written confirmation of the allocation once made. A seller who cannot produce the first two is selling an intention.
One honest uncertainty: the off-site market is still young, pricing varies widely by region and habitat type, and comparable evidence is thin. Treat any single quoted price as a data point rather than a market rate, and get more than one offer.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
When do off-site biodiversity units count?
Only once the land is entered on the biodiversity gain sites register, the habitat is secured for at least 30 years by a conservation covenant or a planning obligation, and the units have been allocated to your development by its planning application reference. An unregistered unit cannot support approval of a biodiversity gain plan.
Who operates the gain sites register?
Natural England. The entry records the land and title, the habitat before and after enhancement, the units calculated with the statutory metric, the responsible person, the legal mechanism securing the land, the management and monitoring plan, and every allocation made to a named development. Registration and allocation fees are set in regulations.
Is a conservation covenant better than a section 106?
Usually quicker on cross-boundary deals. A conservation covenant is made with a responsible body designated by Defra and binds successors in title. A section 106 obligation needs the local planning authority where the gain site sits to be a party, which is often a different authority from the one deciding your application.
Why does the location of the gain site change the price?
Because the metric discounts units according to distance. Units in the same authority area or National Character Area carry no spatial reduction, while units further away are discounted, so more have to be bought to deliver the same net gain. Apply the discount before comparing offers rather than after.
Can I use land I already own as a gain site?
Yes, provided it is not land you are relying on for the on-site baseline and the legal position allows. Check agricultural tenancies, grazing agreements and existing agri-environment scheme commitments first, and remember you are taking on a 30-year management liability together with the registration work and monitoring.
What should I ask a unit provider for?
The register entry number, the executed conservation covenant or planning obligation, the habitat management and monitoring plan, the metric output showing the units claimed and their habitat types, and written confirmation of allocation to your application reference. A provider who cannot produce the legal agreement is selling an intention.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.