BIODIVERSITY NET GAIN · UNITS AND CREDITS
BNG Units and Statutory Biodiversity Credits Explained
Understand the difference between habitat units, private off-site units and government statutory biodiversity credits.
The statutory biodiversity metric measures habitat losses and gains through distinct area, hedgerow and watercourse unit categories. Registered private off-site biodiversity gains are not government statutory credits.
Statutory credits are a last-resort mechanism where the applicable on-site and off-site routes cannot deliver the required gain. ACP can review metric and planning evidence; the developer makes any statutory-credit purchase directly through the official service.
BNG Units and Credits at a Glance
The words unit and credit are often used loosely. However, they have different meanings in the statutory BNG system.
| Term | What it means | Where it comes from | Key point |
|---|---|---|---|
| Biodiversity unit | A standard measure of biodiversity value calculated by the Statutory Biodiversity Metric. | Existing, created or enhanced habitat. | A unit is a measurement. It is not automatically a product for sale. |
| Off-site biodiversity unit | Biodiversity gain delivered away from the development site and allocated to the development. | A registered gain site on the developer’s own land or land provided by another land manager. | Off-site gains form part of the normal unit-delivery route. However, the metric’s spatial risk rules can affect their value. |
| Statutory biodiversity credit | A government-provided fallback used where the required BNG cannot be delivered through the applicable on-site and off-site routes. | Purchased through the official statutory-credit service. Natural England sells credits on behalf of Defra. | Credits are a last resort. The statutory-credit spatial risk multiplier means developers need two credits for every biodiversity unit they compensate. |
Use precise terminology
Private off-site gains are officially discussed as biodiversity units, not statutory credits. Some market material uses “credits” informally, so always check which mechanism is actually being offered.
Key point: a biodiversity unit measures value. An off-site unit delivers registered habitat gain. A statutory credit is a separate government fallback.
What Is a Biodiversity Unit?
A biodiversity unit is the standardised measure used by the Statutory Biodiversity Metric to calculate biodiversity value for BNG in England.
The metric compares habitats before development with those that the project will retain, create or enhance afterwards. Its calculations use factors including habitat size, type, condition and strategic significance. For created or enhanced habitats, the metric also considers delivery difficulty, the time needed to reach target condition and spatial risk where relevant.
The metric then shows whether the development achieves the required biodiversity gain and whether any unit shortfall remains.
For a full metric calculation service, see ACP’s Statutory Biodiversity Metric page:
Explore the Statutory Biodiversity Metric
Three separate unit types
The statutory metric treats three unit types separately:
Area habitat units
These cover area-based habitats such as grassland, woodland, wetland and urban habitats.
Hedgerow units
These measure hedgerow losses and gains within the hedgerow module.
Watercourse units
These measure relevant rivers, streams, canals, ditches and other watercourse features within the watercourse module.
The unit types are not interchangeable. A surplus of hedgerow units cannot simply replace a shortfall in area habitat units, for example. The project must satisfy the 10% objective and metric trading rules within the relevant unit type.
A unit is not “one hectare”
There is no fixed number of biodiversity units per hectare or acre. Two sites of the same size can have very different unit values because their habitats, condition and other metric factors differ.
Therefore, use the statutory metric rather than generic “units per acre” assumptions.
How Off-Site Biodiversity Units Work
The off-site route
Where the BNG strategy uses habitat away from the development site, the gain is treated as off-site biodiversity gain.
A developer can make off-site gains on other land it controls or secure units from another land manager. The gain site must meet the statutory registration and allocation requirements before the units can count towards the development’s BNG position.
Off-site units also need to satisfy the metric’s trading rules. In addition, the spatial risk multiplier can reduce the unit value delivered to a development when the gain site is farther from the impact site.
For area and hedgerow units, the metric uses local planning authority and National Character Area relationships. Different spatial rules apply to watercourses.
Off-site units are not statutory credits
Buying an off-site biodiversity unit does not mean buying a statutory biodiversity credit.
Off-site units come from habitat creation or enhancement at a registered gain site. Statutory credits are the government fallback used when the applicable on-site and off-site routes cannot deliver the required BNG.
For help with the commercial off-site route, see Off Site Biodiversity Units:
Read our off-site biodiversity units guide
If you need the gain-site registration and allocation process, see Biodiversity Gain Site:
Understand gain-site registration
To compare the legal securing routes, see Conservation Covenant vs Section 106:
Compare Section 106 agreements and conservation covenants
When Can Statutory Biodiversity Credits Be Used?
Statutory biodiversity credits are a last-resort route. They are not a substitute for carrying out the BNG assessment or considering the other delivery options that apply to the development.
For major development, the Biodiversity Gain Hierarchy prioritises compensation through on-site enhancement and creation, then registered off-site gains, before statutory credits.
For qualifying non-major planning applications made on or after 6 August 2026, the hierarchy changed. The hierarchy gives on-site enhancement, on-site creation and registered off-site biodiversity gain the same preference. Statutory biodiversity credits still remain the final option when those actions cannot be done.
The previous hierarchy continues to apply in the transitional cases set out in current planning guidance. Irreplaceable habitats also have separate treatment. Where bespoke compensation is required, statutory credits cannot replace it.
Decision pathway
- Is the development subject to statutory BNG?If no, the statutory-credit route does not apply through the mandatory BNG condition. Check the project’s actual exemption or planning position.
- Has the Statutory Biodiversity Metric identified the required BNG and any remaining shortfall?If no, complete the appropriate metric work first.
- Can the shortfall be addressed through the on-site and/or registered off-site actions allowed by the applicable Biodiversity Gain Hierarchy?If yes, use those routes. Statutory credits are not the default choice.
- If those routes cannot meet the required BNG, can the developer evidence why statutory credits are needed?Current statutory-credit guidance requires evidence in the Biodiversity Gain Plan.
- Has the local planning authority confirmed that statutory credits can be used?Discuss the proposed credit route with the LPA before purchase.
- Has planning consent been granted and is the developer ready to progress the Biodiversity Gain Plan?The current purchase service requires evidence of planning consent.
- The developer purchases the required statutory credits through the official service.The purchase cannot be made by an agent or representative on the developer’s behalf.
Key point: statutory credits are a safety-net mechanism, not a shortcut around the normal BNG strategy.
What Evidence Is Needed Before Statutory Credits?
Explain why credits are necessary
Current government guidance requires the Biodiversity Gain Plan to explain why statutory credits are needed.
The developer should provide:
- Evidence that on-site BNG was considered, together with the reasons it cannot provide the required outcome.
- Evidence that three local or national suppliers, habitat banks or trading websites were approached and that insufficient off-site options are available in England.
For example, the evidence can include correspondence or a saved record of a marketplace search.
Small shortfalls below 0.25 units
There is a limited evidence relaxation for very small statutory-credit requirements.
If the developer needs less than 0.25 biodiversity units, current statutory-credit guidance says they can buy statutory credits without providing the second evidence step above about insufficient off-site supply.
However, the project still needs to follow the wider statutory-credit process and the applicable Biodiversity Gain Plan requirements.
Do not confuse the evidence test with private unit sourcing
This page explains the government evidence requirement. However, it does not replace commercial due diligence where a project is buying private off-site biodiversity units.
For the off-site unit route, use ACP’s Off Site Biodiversity Units guidance:
Review the off-site unit procurement process
How the 2:1 Statutory Credit Multiplier Works
Statutory biodiversity credits receive a spatial risk multiplier of 0.5.
That means one statutory credit counts as 0.5 biodiversity units. Therefore, the developer must buy two statutory credits for every one biodiversity unit that needs to be compensated through the statutory-credit route.
The Statutory Biodiversity Metric already applies this in its credit calculation output. Therefore, do not manually double a figure from the metric’s statutory-credit output.
Worked example
Assume the metric identifies an A1 statutory-credit requirement equivalent to a 1.50-unit shortfall.
- Biodiversity-unit shortfall: 1.50 units
- Statutory-credit multiplier: 2 credits per unit
- Statutory credits required: 3.00 A1 credits
- Current A1 price: £42,000 per credit
- Illustrative statutory-credit cost: £126,000
This example explains the statutory mechanism only. It is not a project quotation and does not compare private off-site unit prices.
For wider BNG cost and pricing guidance, see BNG Costs & Pricing:
See the wider BNG costs and pricing guide
Current Statutory Biodiversity Credit Prices
Defra publishes fixed statutory biodiversity credit prices by habitat tier. The price list was last updated on 2 June 2026 and remained the current official list when this page was reviewed on 14 October 2026.
The table separates the price per statutory credit from the illustrative cost of two credits for one biodiversity unit. The second cost column applies the 2:1 multiplier once.
| Statutory credit tier | Habitat unit group | Current price per credit | Illustrative cost per unit 2 statutory credits |
|---|---|---|---|
| A1 | Area habitats | £42,000 | £84,000 |
| A2 | Area habitats | £48,000 | £96,000 |
| A3 | Area habitats | £66,000 | £132,000 |
| A4 | Area habitats | £125,000 | £250,000 |
| A5 | Area habitats | £650,000 | £1,300,000 |
| H | Hedgerows | £44,000 | £88,000 |
| W | Watercourses | £230,000 | £460,000 |
The metric’s credit output identifies the tier and quantity required for the development. Defra reviews credit prices every six months. It deliberately sets them so they do not undercut the private off-site market.
Statutory-credit prices are not guideline prices for private off-site biodiversity units.
Always check the current GOV.UK price list before relying on a figure for a live project.
EXPLORE AN INDICATIVE COST
Statutory credit cost calculator
Use the tiers from your statutory metric to explore an indicative government-credit cost. Enter a quantity for each relevant tier; leave the others blank.
Unit mode doubles each quantity once. If the metric already gives statutory credits, select credit mode to avoid doubling again.
Use zero or positive quantities, with up to two decimal places. Tier and unit category must come from the metric; the calculator cannot determine them.
INDICATIVE GOVERNMENT-CREDIT COST
—
Add your quantities, then select Calculate estimate.
Government statutory credits only. This is not a private off-site unit price or an ACP quotation.
Before you rely on an estimate: confirm eligibility, habitat tiers and quantities using the current statutory metric and official guidance. This calculator does not assess the site, confirm that credits are available to your project, or replace the Biodiversity Gain Plan. Consultancy and other project costs are excluded.
Prices checked on 14 October 2026. Check the current government credit prices. Fractional credits use two decimal places; the final purchase must follow the metric output and official service.
How to Buy Statutory Biodiversity Credits
Once the developer has justified the statutory-credit route, they should follow the current official process.
Confirm the number and tier of credits
Use the Statutory Biodiversity Metric to identify the statutory-credit requirement. The metric groups the requirement into area tiers A1–A5, hedgerow tier H and watercourse tier W.
Check the current statutory-credit cost
Use the current GOV.UK price list or statutory-credit cost estimator. Prices can change, so check them again when preparing the purchase.
Discuss the credit route with the local planning authority
Before purchase, ask the LPA to confirm that the development can use statutory credits.
Make sure planning consent is in place
The current purchase service requires evidence of planning consent. For a normal Town and Country Planning Act development, this means the relevant planning approval notice.
The developer applies through the official service
The purchase application requires the statutory metric, development details and the credit quantities shown by the metric.
GOV.UK states that an agent or representative cannot act on the developer’s behalf to buy statutory biodiversity credits.
ACP can help you understand the metric, prepare the supporting BNG evidence and check the strategy. However, the statutory-credit purchase must be made through the developer’s own official application route.
Allow for the government approval process
Current statutory-credit guidance says an application can take up to eight weeks to approve. Following approval, Natural England issues an invoice for the credit cost.
Statutory-credit purchases are non-refundable, so do not buy them prematurely.
Submit proof of purchase with the Biodiversity Gain Plan
After payment, retain the proof of purchase for the Biodiversity Gain Plan and discharge of the biodiversity gain condition.
Key point: statutory-credit purchase sits late in the BNG process. It follows the metric, planning consent, evidence and LPA discussion rather than replacing them.
What ACP Can Help With
ACP can support the technical and planning work that sits around a BNG unit shortfall.
Metric review and shortfall explanation
First, we can review the current Statutory Biodiversity Metric and explain the remaining area, hedgerow or watercourse unit position.
On-site and off-site strategy review
Next, we can help you understand whether the project can address its shortfall through the on-site and registered off-site routes that apply to the development.
Statutory-credit evidence support
Where statutory credits may be necessary, we can help organise the ecological and planning evidence needed to explain the route within the Biodiversity Gain Plan.
Planning and BNG coordination
Finally, we can help align the unit position with the wider BNG strategy and supporting documents. However, questions of legal interpretation may also require separate legal advice.
Need your unit shortfall reviewed?
Send ACP the latest statutory metric, site location and current planning position. We can explain the remaining BNG requirement and the next technical steps.
Frequently Asked Questions About BNG Units and Statutory Credits
Clear answers on units, eligibility and the statutory-credit process.
What is a biodiversity unit in BNG?
A biodiversity unit is the standard measure used by the Statutory Biodiversity Metric to quantify biodiversity value. The metric calculates units for the existing habitat baseline and the proposed post-development position.
A unit is not a fixed area of land. Instead, its value depends on the habitat and the metric inputs that apply to it.
What is the difference between an off-site biodiversity unit and a statutory biodiversity credit?
An off-site biodiversity unit comes from habitat gain delivered away from the development site and allocated to the development through the statutory off-site system.
A statutory biodiversity credit is a government fallback. It can be used only when the required BNG cannot be delivered through the applicable on-site and off-site routes.
Are private off-site biodiversity units the same as “BNG credits for sale”?
Not in strict statutory terminology.
Private-market gains are off-site biodiversity units. The term statutory biodiversity credit refers to the government mechanism sold by Natural England on behalf of Defra.
Some suppliers use “credits” informally, so confirm which mechanism is actually being offered.
Can I choose statutory biodiversity credits because they are simpler?
No. Statutory credits are a last-resort mechanism.
The developer must follow the applicable Biodiversity Gain Hierarchy and provide the evidence required by current statutory-credit guidance. The LPA should confirm that credits can be used before purchase.
Has the Biodiversity Gain Hierarchy changed for small or non-major development?
Yes, for qualifying non-major planning applications made on or after 6 August 2026.
For those applications, the hierarchy gives on-site enhancement, on-site creation and registered off-site gains the same preference. Statutory biodiversity credits remain the final option.
However, developers must still check transitional and other project-specific provisions.
How many statutory credits do I need for one biodiversity unit?
Developers need two statutory biodiversity credits for every biodiversity unit they compensate through the statutory-credit route.
The metric applies the statutory-credit spatial risk multiplier automatically. One statutory credit therefore counts as 0.5 biodiversity units.
What evidence do I need before using statutory credits?
Current guidance requires the Biodiversity Gain Plan to show that on-site BNG was considered and why it cannot deliver the required result.
It also normally requires evidence that three local or national suppliers, habitat banks or trading websites were approached and that insufficient off-site options are available in England.
If the requirement is less than 0.25 biodiversity units, the second supplier-evidence step is not required under the current statutory-credit guidance.
Can ACP buy statutory biodiversity credits for me?
No. Current GOV.UK guidance says an agent or representative cannot act on a developer’s behalf to buy statutory biodiversity credits.
ACP can review the metric, unit shortfall, BNG strategy and supporting evidence. However, the developer must make the statutory-credit purchase through the official service.
When should statutory biodiversity credits be bought?
Do not buy them too early.
Current guidance says purchases are non-refundable and developers should not purchase credits until they are ready to submit the Biodiversity Gain Plan and discharge the biodiversity gain condition. The purchase service also requires evidence of planning consent.
How much do statutory biodiversity credits cost?
Current official prices range by tier. The price list reviewed for this page runs from £42,000 per A1 credit to £650,000 per A5 credit, with separate H and W prices for hedgerow and watercourse credits.
Because developers need two statutory credits for every biodiversity unit, the total cost of compensating a unit can be substantially higher than the headline price per credit.
Always check the current GOV.UK price list before relying on a figure.
Are area, hedgerow and watercourse units interchangeable?
No. The statutory metric treats area habitat, hedgerow and watercourse units as separate types.
Do not add together, trade or convert different unit types. The metric also applies trading rules within each module.
Can a distant off-site unit be worth less to my development?
Yes. The statutory metric applies a spatial risk multiplier to off-site gains based on the relationship between the impact site and the gain site.
For area and hedgerow units, location within the same or neighbouring local planning authority or National Character Area is relevant. Watercourses use catchment-based spatial rules.
Discuss Your BNG Unit or Credit Position
Tell us your development location, metric position and whether off-site units or government credits are being considered.
You do not need every document before contacting us. Please summarise what you have; we can discuss how to share supporting information securely if a review is appropriate.
Your project, site location and contact details can be provided through the enquiry form.
Prefer to talk? 0330 236 7329 · hello@acp-consultants.com.
Sources and scope
The following official guidance was checked on 14 October 2026. Guidance, government fees, legal requirements and statutory-metric tools may change.
Statutory biodiversity credits · Statutory biodiversity credit prices · Buying statutory biodiversity credits · Understanding BNG.
Scope of this guide. This explains statutory BNG unit types and government biodiversity credits; it is not an offer to sell credits. Statutory credits are a last-resort mechanism and the developer must use the current official purchase process. Project-specific metric, planning and evidential requirements may differ.
This information supports initial ecological and planning discussions in England. It does not determine a planning outcome or replace project-specific ecological, planning, legal or commercial advice.
Disclaimer date: October 2026.