A biodiversity gain plan: section by section
The biodiversity gain plan is submitted after permission and before development begins. Section by section, what it must contain and where authorities refuse them.
A biodiversity gain plan is the document that lets you start. Schedule 7A to the Town and Country Planning Act 1990, inserted by the Environment Act 2021, deems a biodiversity gain condition onto most planning permissions in England, and that condition prevents development beginning until the authority has approved a gain plan. It is not part of the application. It comes afterwards, and it is the last thing standing between a permission and a start on site.
Which is exactly why it goes wrong. Teams that fought the metric at application stage treat the plan as a formality, submit it four weeks before the contractor mobilises, and then discover the authority disagrees with the baseline.
What the plan is and when it goes in
The gain plan is a submission to the local planning authority, made after permission is granted and before development begins. It sets out what the site was worth in biodiversity units, what it will be worth afterwards, how the 10 per cent uplift is achieved, and what has been done to reduce harm along the way.
There is no single national form, though authorities increasingly use the standard template. What matters is that every element the legislation requires is present and evidenced, because a plan missing one of them is refused rather than negotiated.
Submit it eight to twelve weeks before you need to start. The authority has a set period to determine it, commonly eight weeks unless a longer period is agreed, and a refusal followed by a resubmission doubles that.
Recording the pre-development biodiversity value
This is the section that decides everything downstream, because the uplift is measured against it.
The value is calculated using the statutory metric on the habitats present at the relevant date, which is normally the date of the planning application rather than the date of the gain plan. State that date explicitly and evidence the habitat condition at that date with the survey records, photographs and mapping the ecologist relied on.
Two traps sit here.
The first is degradation. Where activities carried out on or after 30 January 2020 reduced the biodiversity value of the land, and those activities were not themselves authorised, the pre-development value is taken as the value immediately before those activities. Clearing scrub to make a site look tidy before survey is the classic error, and authorities do check aerial imagery.
The second is the survey season. A baseline built from a February walkover on grassland will be challenged, because condition assessment for grassland needs the growing season. Where the habitat baseline came from a preliminary ecological appraisal carried out at the wrong time of year, expect to be asked for a resurvey, and expect that to cost a season.
The post-development value and the trading rules
The proposed value has to be calculated with the same version of the metric, on the same site boundary, using the habitat types the landscape design actually delivers.
The metric's trading rules constrain what you can substitute for what. Habitats of higher distinctiveness must be replaced with the same habitat type, or with something of higher distinctiveness, and you cannot make up a loss of species-rich grassland with amenity lawn however many square metres you provide. Condition, strategic significance, difficulty of creation, time to target condition and off-site location all apply multipliers, and the delay multiplier in particular punishes habitats that take decades to reach target condition.
Three things make this section convincing:
- A habitat plan drawn at a legible scale, keyed to the metric rows, with areas that add up.
- A management prescription for each created or enhanced parcel, stating target condition and the interventions that reach it.
- A statement of who holds the land and how the management is funded for 30 years.
Where the landscape design is doing the heavy lifting, the Landscape Strategy and the gain plan have to say the same thing. Two documents describing different planting is the most common internal contradiction officers find.
On-site, off-site and statutory credits
The hierarchy runs in one direction. Deliver gains on site where you can, then off site through registered gains allocated to the development, then, as a last resort, buy statutory biodiversity credits from the government.
Set out in the plan which route delivers which part of the uplift, with the numbers reconciling to the metric output. For off-site gains, give the register reference, the responsible body or the section 106 agreement securing it, and the date the allocation was made. For credits, state the tier and the number purchased.
Credits are deliberately priced to be the expensive option, so a plan relying on them for most of the uplift invites the question of why on-site delivery was not possible. Answer it in the plan rather than waiting to be asked: site constraints, contamination, the density required by the permission.
The 30-year obligation is the part clients underestimate. On-site gains of the kind the regulations treat as significant have to be secured for 30 years through a planning condition, a section 106 obligation or a conservation covenant, with monitoring and reporting. Budget for the management, and make sure the estate management company or the adopting body knows what it is taking on.
Irreplaceable habitat
Ancient woodland, ancient and veteran trees, blanket bog, limestone pavement and the other habitats listed in the regulations sit outside the metric trading system.
Where the development affects irreplaceable habitat, the gain plan has to say so, and it must set out the arrangements made for compensating for the loss, agreed with the authority. The metric does not produce a number that makes this acceptable, and national policy sets a high bar against the loss in the first place.
If irreplaceable habitat is present, deal with it at design stage. A gain plan is not the place to discover it.
Steps taken to minimise adverse effect
The plan must record the steps taken to minimise the adverse effect of the development on the on-site biodiversity value. This is the mitigation hierarchy in documentary form: avoid, then minimise, then restore, then compensate.
Write it chronologically and concretely. The hedgerow retained when the access was moved north. The veteran tree buffered by 15 times its stem diameter. The construction exclusion zone around the pond. The lighting designed to keep the commuting corridor dark.
Vague statements here weaken the whole plan, because this is the section an authority ecologist reads to judge whether the numbers were arrived at honestly. A Biodiversity Net Gain Assessment prepared at application stage should already carry most of this narrative, and the gain plan updates it rather than starting again.
Getting it approved without a round trip
The refusals that cost most are procedural rather than ecological.
- Use the current version of the statutory metric, and say which version you used. Metric updates change results.
- Submit the metric calculation file itself, not a screenshot of the summary tab. Authority ecologists check the rows.
- Reconcile every number in the narrative to the metric output. A plan claiming 11.4 per cent in the text and showing 9.8 per cent in the file is refused.
- Name the person who completed the metric and their competence. The Environment Act regime expects a competent person, and this is not a document to have drafted by someone without habitat identification skills.
- Include the secured mechanism, signed, rather than a draft. Off-site allocations that are not yet registered are the commonest reason for a plan being held.
Treat any AI-assisted draft as a structure for that competent person to work within. PlanScope can produce the narrative sections and the policy framing in minutes, and the metric, the survey and the professional judgement remain with the ecologist.
Browse the report types by category to see what an ecology-led application usually carries, or enter your postcode to check the site.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. 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 is a biodiversity gain plan submitted?
After planning permission is granted and before development begins. The biodiversity gain condition deemed onto most permissions prevents any start on site until the authority has approved the plan. Allow eight to twelve weeks, because the authority has a determination period and a refusal followed by resubmission doubles it.
What date is the pre-development biodiversity value measured at?
Normally the date of the planning application rather than the date of the gain plan. Where activities carried out on or after 30 January 2020 reduced the value of the land without authorisation, the value is taken as it was immediately before those activities. Authorities check historic aerial imagery for site clearance.
Can I meet the 10 per cent using statutory credits?
Yes, but only as the last step in the hierarchy after on-site and registered off-site gains. Credits are deliberately priced as the expensive option, so a plan relying on them for most of the uplift should explain why on-site delivery was not possible, citing site constraints or the density the permission requires.
How long do biodiversity gains have to be maintained?
Thirty years for qualifying on-site gains and for off-site gains, secured by planning condition, section 106 obligation or conservation covenant, with monitoring and reporting. Budget the management cost and make sure whoever takes on the land, such as an estate management company, understands the obligation before completion.
What happens if the site contains irreplaceable habitat?
It sits outside the metric trading system. The gain plan must state that irreplaceable habitat is present and set out the compensation arrangements agreed with the authority. National policy sets a high bar against the loss in the first place, so this is a design-stage issue rather than a gain plan issue.
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.