What is the Gain Sites Register?
The Biodiversity Gain Sites Register is the official national database maintained by Natural England that records all registered off-site BNG habitat bank sites in England. It is the authoritative public record — if an off-site gain site isn't on this register, its units cannot legally be allocated to a development's Biodiversity Gain Plan.
The register serves two critical functions in the BNG market:
- For developers: It's where they search for and verify off-site biodiversity units to purchase. LPAs will check that any off-site allocations cited in a Biodiversity Gain Plan are recorded on this register before approving the plan.
- For landowners: Getting listed on the register is the essential step that makes a habitat bank's units available for sale to developers. Without registration, units cannot be legally allocated to developments.
What the register contains
The public register, published via DEFRA's open data API, provides the following data for each registered gain site:
| Data point | Available? | Detail |
|---|---|---|
| Site reference number | Yes | A unique identifier for each registered site (e.g., "BGS-000123") |
| Grid reference / coordinates | Yes | Location data that allows mapping and geographic analysis |
| National Character Area (NCA) | Yes | Which of the 159 NCAs the site falls within — essential for trading rule matching |
| Responsible body | Yes | The organisation monitoring the site's conservation covenant or S106 compliance |
| Registration date | Yes | When the site was added to the register |
| Allocation records | Partial | Which developments have been allocated units from the site (recorded when allocations are made) |
What the register does NOT contain
This is where it gets commercially significant. The public register omits several data points that are essential for anyone trying to make informed decisions in the BNG market:
What you can find
- ✓Site reference number
- ✓Grid reference / map location
- ✓National Character Area
- ✓Responsible body name
- ✓Registration date
- ✓Allocation records (partial)
What's missing
- ✗Biodiversity unit quantities (area, hedgerow, watercourse)
- ✗Habitat types and parcel breakdown
- ✗Human-readable site name
- ✗Legal agreement type (covenant vs S106)
- ✗Site area in hectares
- ✗Habitat condition assessments
- ✗Available stock (units remaining for sale)
- ✗Pricing information
- ✗Landowner / operator contact details
Why is this data missing?
The detailed habitat data — unit quantities, habitat types, condition assessments — is contained in the DEFRA Statutory Biodiversity Metric 4.0 files (.xlsm) that landowners submit as part of their registration application. These files are not published through the public register API. DEFRA's open data release was designed as a statutory record, not a commercial marketplace tool.
The result is a market where the most commercially important information — what's actually for sale and in what quantity — is invisible to both buyers and the wider market. Developers must contact individual sites or brokers to find out what's available, making the process slow, opaque, and inefficient.
How the register is used in practice
For developers purchasing off-site units
When a developer needs off-site biodiversity units, the workflow typically involves:
- Calculating the unit shortfall from the statutory metric (by trading tier and habitat type)
- Searching for registered gain sites in the same LPA or NCA
- Contacting site operators or brokers to enquire about availability, habitat types, and pricing
- Agreeing terms and reserving units
- Recording the allocation on the register (the landowner or developer can do this with consent)
- Including the allocation reference in the Biodiversity Gain Plan for LPA approval
The LPA will check that the allocation is correctly recorded on the register before approving the gain plan. This is a critical verification step — without a confirmed allocation on the register, the gain plan cannot be approved and development cannot commence.
For LPAs checking allocations
When assessing a Biodiversity Gain Plan, the LPA verifies:
- That the off-site gain site cited in the plan is registered on the national register
- That the unit allocation is correctly recorded against the development
- That the allocation matches the unit quantities and types shown in the developer's metric calculation
How to register a gain site
If you're a landowner looking to register your land as a biodiversity gain site, the process follows these steps:
- 1Legally secure the land. Enter into a conservation covenant (with a designated responsible body) or a Section 106 agreement (with your LPA) committing to at least 30 years of habitat management.
- 2Agree a Habitat Management and Monitoring Plan (HMMP) with the responsible body or LPA, setting out how habitats will be created, managed, and monitored over the 30-year period.
- 3Apply to Natural England to register your land. Submit the required documentation including your completed metric file, legal agreement, and HMMP.
- 4Natural England assesses your application against the eligibility criteria. They review the legal agreement, metric calculations, and management plan to ensure they meet the required standards.
- 5If approved, your site appears on the public register. You can now begin selling biodiversity units to developers.
- 6Record allocations as you sell units. Either you or the developer can record allocations on the register (with your consent). The LPA will check these before approving the developer's gain plan.
The register and the off-site market
The Gain Sites Register is the backbone of the off-site BNG market, but the market has developed around its limitations rather than because of them:
Current market dynamics
- 197 registered sites as of early 2026, up from 46 just one year earlier — a fourfold increase showing rapid market growth
- ~28,000 habitat units available nationally across registered sites
- ~1,500 units sold to date, indicating healthy supply but early-stage demand
- 107 of 309 LPAs have at least one registered habitat bank — leaving 202 LPAs with no local off-site supply
- ~300 allocations delivered to non-local LPAs/NCAs, showing that geographic supply gaps are forcing cross-boundary trading
Geographic coverage gaps
The most significant market challenge revealed by the register is geographic unevenness. While national supply is healthy (28,000 units far exceeds the ~1,500 sold), the supply is concentrated in certain areas. Developers in the 202 LPAs with no registered habitat banks face a constrained market — they must either source units from adjacent NCAs (less geographically preferred under the trading rules) or resort to statutory credits at a significant cost premium.
This geographic gap is both a challenge for developers (higher costs, longer sourcing timescales) and an opportunity for landowners in underserved areas. A new habitat bank in an LPA with no existing supply has a captive local market.
The growing role of data intermediaries
The information gap in the public register has created demand for data intermediaries — platforms that enrich the basic register data with the commercially critical information that DEFRA doesn't publish.
An effective BNG intelligence platform connects the dots that the register leaves disconnected:
- Unit data: How many area, hedgerow, and watercourse units each site has generated
- Habitat profiles: What habitat types are available, at what distinctiveness tier, enabling trading rule matching
- Available stock: Total units minus allocations — how many units are still available for purchase
- LPA-level analytics: Supply and demand by geographic area, identifying gaps and opportunities
- Planning linkage: Connecting gain sites to the planning applications and developments they serve
- Market pricing: Benchmark pricing data by habitat type and geography
This enrichment transforms the register from a static statutory record into an actionable market intelligence tool — enabling developers to find the right units faster, landowners to position their sites more effectively, and LPAs to understand their local market dynamics.
Searching the register
There are several ways to access the register data:
| Method | What you get | Best for |
|---|---|---|
| GOV.UK search | Basic search of registered sites by location | Quick checks on whether sites exist in a specific area |
| DEFRA open data API | Machine-readable data for all registered sites (JSON) | Developers, researchers, and platform builders needing bulk data |
| Postcode Lookup (this site) | LPA identification and indicative supply check for any postcode | Quick geographic context — try it here |
| ectare.dev | Enriched data with unit quantities, habitat types, LPA analytics, and market intelligence | Professional decision-making — sourcing units, positioning sites, market analysis |
Key facts about the register
- Maintained by Natural England on behalf of DEFRA
- Sites can only be registered once the land is legally secured (conservation covenant or S106) for at least 30 years
- Natural England assesses all applications against eligibility criteria before listing
- Allocations (units sold to specific developments) are recorded on the register — LPAs check these
- Sites can be removed from the register (the API includes a removal date field, currently null for all active sites)
- The register is public — anyone can search it or access it via the open data API
- Registration does not commit the landowner to sell units immediately
- The register does not publish unit quantities, habitat types, pricing, or contact details
What's likely to change
As the BNG market matures, the register is likely to evolve:
- More data fields: Pressure is growing for DEFRA to publish more commercially useful information, though privacy and market competition concerns may limit this
- NSIP demand from May 2026: The extension of BNG to Nationally Significant Infrastructure Projects will drive significantly more registrations and allocations through the register
- Market standardisation: As the off-site market matures, more standardised data formats and trading protocols are likely to emerge around the register
- Private market enrichment: Platforms like ectare.dev are filling the data gaps that DEFRA has chosen not to, creating a de facto enriched register that operates alongside the statutory one