The biodiversity gain plan: what it must contain
The biodiversity gain plan is the document a developer submits after planning permission and before starting work, showing how the 10% net gain will be delivered. It must contain the completed metric, baseline and post-development habitat information, on-site enhancement and management details and the register evidence for any off-site units or credits. Development cannot lawfully begin until the planning authority approves it.
Key facts
- Submitted after permission is granted and before development begins; the authority has eight weeks to decide.
- Must use the statutory biodiversity metric and show at least 10% gain for each unit type present.
- Off-site units must be allocated on the biodiversity gain site register before approval.
- On-site habitat must be secured for 30 years by condition, Section 106 agreement or conservation covenant.
- Draft gain plans are often accepted at application stage; the final plan follows permission.
Last checked: 3 October 2026
What goes in the plan?
| Section | Content |
|---|---|
| Pre-development biodiversity value | Metric baseline, survey date, habitat plan, condition assessments |
| Post-development value | Habitat retained, created and enhanced on site, with target conditions |
| Off-site gains | Registered site reference, units allocated by type, legal agreement |
| Statutory credits | Any credits purchased and the evidence that units were not available |
| Hierarchy | How harm was avoided and on-site options considered (equal footing for minor development) |
| Management | How on-site habitat is secured and monitored for 30 years |
Where do off-site units fit?
They are entered in the metric against the registered gain site and evidenced with the allocation confirmation. The allocation must be complete before the plan is approved, which is why sourcing should start well before permission. If you wait until the condition is live, the eight-week clock and scarce supply can collide.
Common reasons plans are refused
- Metric errors, including the wrong multiplier.
- Off-site units not yet allocated or of the wrong type.
- On-site habitat with no credible 30-year management or funding.
- Inconsistency between the plan and the approved drawings.
A gain plan timeline
| Stage | What happens |
|---|---|
| Application | Metric and draft gain plan submitted with the planning application (draft often accepted) |
| Permission | Granted with the general biodiversity gain condition |
| Sourcing | Off-site units allocated on the register |
| Submission | Final gain plan submitted with allocation evidence |
| Decision | Authority approves or refuses within eight weeks |
| Commencement | Development may begin once approved |
Phased developments
Where permission is phased, a gain plan is submitted for each phase and off-site units are allocated phase by phase. Forward allocation agreements keep later phases covered without buying everything up front.
Who can submit the plan
The person who is to carry out the development, usually the applicant or their successor, submits the plan. A later purchaser of the site can submit it as the developer. Where the site is sold with permission, make the metric, surveys and any forward allocation part of the sale pack so the buyer can complete the plan.
Key takeaways
- Submitted after permission, before development begins
- Eight weeks for the authority to decide
- Off-site units must be allocated before approval
- Phased schemes submit a plan per phase
Frequently asked questions
Can I start enabling works before approval?
Generally no. Development must not begin until the plan is approved, apart from limited exceptions set out in the regulations.
Who approves the plan?
The local planning authority, within eight weeks of submission.
Does the plan cover NSIPs?
NSIPs use a biodiversity gain statement and plan secured through the development consent order.
Can the plan be amended?
Yes, with the authority’s approval, for example if phasing changes.
Can I submit the gain plan with the application?
A draft, yes. The final plan follows permission.
What if the authority does not decide in eight weeks?
The applicant and authority can agree an extension; the plan is not deemed approved by default.
Sources
- Biodiversity gain plan guidance, gov.uk
- Biodiversity net gain guidance, gov.uk
- Environment Act 2021, Schedule 7A, legislation.gov.uk
Written by BNG Sourced by Green Acres BNG specialists and reviewed by Mike Dungait, Managing Director of Green Acres BNG, who has registered and manages two habitat banks. Indicative information, not legal or planning advice. Confirm with your ecologist and planning authority.
Related: BNG sourcing check, exemption checker, BNG unit prices, glossary, ecologist evidence checklist, how to buy off-site BNG units.
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