The biodiversity gain condition on every permission
The biodiversity gain condition is deemed into the permission, so it will not appear on the decision notice. What the plan must contain, the exemption routes, and what happens if it is refused.
Every planning permission granted in England for development within the regime carries the biodiversity gain condition whether or not the decision notice mentions it. Schedule 7A to the Town and Country Planning Act 1990, inserted by the Environment Act 2021, deems the condition into the permission: development may not begin until a biodiversity gain plan has been submitted to and approved by the planning authority. You will not find it in the list of conditions, and its absence from that list means nothing.
That single point catches developers who read a decision notice, count the pre-commencement conditions and programme accordingly. The gain plan is an extra approval before a spade goes in, and it is an approval that can be refused.
Where the deemed condition comes from
The Environment Act 2021 did not create a new type of condition to be imposed case by case. It inserted a schedule into the 1990 Act that attaches the requirement to the grant itself. The requirement took effect for major development on 12 February 2024 and for small sites on 2 April 2024, with separate arrangements for nationally significant infrastructure projects on their own timetable.
The substantive obligation is a gain of at least 10 per cent in biodiversity value, measured with the statutory biodiversity metric, secured and maintained for at least 30 years. The deemed condition is the enforcement mechanism: it converts a policy target into something that stops development starting.
Because it is a condition, starting without an approved plan is a breach of condition. A breach of condition notice carries no right of appeal, which makes this one of the least forgiving procedural traps in the current system.
What the biodiversity gain plan has to contain
The plan is a document about arithmetic and evidence rather than a narrative. It has to set out:
- The pre-development biodiversity value of the onsite habitat, and the date it was assessed.
- The post-development value of the onsite habitat.
- Any registered offsite biodiversity gains allocated to the development, with the register details.
- Any statutory biodiversity credits purchased.
- The steps taken and to be taken to minimise the adverse effect of the development on the onsite habitat, which is the mitigation hierarchy written down.
- The details of the planning permission it relates to.
Two dates matter more than the rest. The pre-development value is assessed at the relevant date, normally the date of the application, and where onsite habitat has been degraded on or after 30 January 2020, the value is taken as it was before the degradation. That provision exists because clearing a site before applying was an obvious way to game the metric, and it applies whether or not the clearance was deliberate.
Completing the statutory metric is work for a competent person under the Environment Act regime, and the biodiversity gain plan is approved by the local planning authority. A Biodiversity Net Gain Assessment drafted with AI assistance is a starting point for that competent person, never a substitute for them, and the habitat classification and condition assessment underneath the metric needs someone who can defend it.
Who approves it, and when
The planning authority that granted permission approves the plan, and the timetable is set by the regulations rather than by the permission. Build in the assumption that approval takes as long as a discharge of conditions application, and longer where the metric is contested or offsite units are involved.
| Stage | Practical timing |
|---|---|
| Habitat survey and baseline metric | Within the survey season, before the application |
| Gain plan prepared | After permission, using the approved drawings |
| Submission and validation | Immediately on receipt of the decision notice |
| Authority determination | Allow the same period as a conditions discharge |
| Offsite allocation, where used | Before submission, because the register entry is needed |
Schedule 7A provides for an appeal where approval is refused, with the procedure set out in regulations, so check the current position before assuming a refusal is final. What an appeal costs you is time on a site you have already bought and probably already funded.
Exemptions, and how to claim them
The exemptions are set out in regulations and they are narrower than site meetings suggest. The ones that come up most are:
- The de minimis exemption, where the development affects less than a stated small area of onsite habitat and no priority habitat.
- Householder development.
- Self-build and custom-build development, subject to a limit on the number of dwellings and the site area.
- Development on a biodiversity gain site itself.
- Urgent Crown development and certain other special categories.
Claiming an exemption is not automatic. State it in the application, with the evidence: measured areas of habitat affected for the de minimis route, or the self-build criteria addressed point by point. Authorities have become sceptical about de minimis claims made without a habitat plan, and a claim rejected after permission leaves you needing a gain plan you never surveyed for.
Permitted development sits outside the regime, and section 73 applications relate back to the original permission, which produces some odd results where an older permission is being varied. Our note on small sites rules that differ works through the small site position in more detail.
The irreplaceable habitat route
Where development affects irreplaceable habitat, as defined in regulations and including ancient woodland and other listed types, the 10 per cent calculation does not apply to that habitat. Instead the plan must include a statement of the bespoke compensation agreed with the authority.
This is a harder route, not an easier one. National policy resists loss of irreplaceable habitat in the first place, so the planning permission itself is the difficult step, and the compensation package has to be negotiated rather than calculated. Early ecological survey work, starting with a Preliminary Ecological Appraisal, is what identifies whether you are in this territory. Councils expect a suitably qualified author for that appraisal and professional review is strongly advised.
Phased development and the overall plan
Large schemes rarely deliver gain phase by phase in a way that adds up on its own, so the regime provides for phased development. The permission carries a requirement for an overall biodiversity gain plan covering the whole site, approved before the first phase begins, and then a plan for each phase.
Getting the overall plan right early is what protects the later phases. If the overall strategy relies on a habitat area that a later phase then builds on, you are back to buying offsite units at the end of the project, at whatever the market charges then. Set the retained habitat out on a constraints plan and treat it as undevelopable from the outset.
Where a scheme is being phased over many years, the 30-year management obligation for each parcel also starts at different times, which the section 106 or conservation covenant has to handle.
If the plan is refused
Three things follow, in this order. Development cannot start. The reasons for refusal will usually be technical, meaning the metric inputs, habitat condition assessment or the durability of the offsite arrangement. And the fix is normally evidence rather than redesign.
Where the refusal is about onsite habitat condition scoring, get the ecologist to a site meeting with the authority's ecology adviser. Where it is about the offsite arrangement, the register entry and the legal agreement are what need attention. Where it is about the mitigation hierarchy, expect to show that avoidance and minimisation were addressed at design stage rather than asserted afterwards, which is why the ecology work belongs before the application rather than after it.
One honest uncertainty: authorities are still building capacity for this work, and determination times for gain plans vary widely. Ask the authority what its current turnaround is before you fix a start date with a contractor. Follow changes on the planning law timeline.
Browse all 66 PlanScope report types and start a draft, then send the ecology documents for professional review.
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
Why is the biodiversity gain condition not on my decision notice?
Because Schedule 7A to the Town and Country Planning Act 1990 deems it into the grant of permission rather than requiring the authority to impose it. Its absence from the list of conditions has no effect. Development still cannot begin until a biodiversity gain plan has been submitted and approved.
What happens if I start work without an approved gain plan?
Starting is a breach of condition. A breach of condition notice carries no right of appeal, and the authority can also decline to treat development as lawfully begun, which has consequences for the life of the permission. It is one of the least forgiving procedural traps in the current system.
When is the pre-development biodiversity value assessed?
At the relevant date, normally the date of the application. Where onsite habitat was degraded on or after 30 January 2020, the value is taken as it stood before the degradation, whether or not the clearance was deliberate. That provision closes off clearing a site to improve the metric baseline.
Which developments are exempt?
The main routes are the de minimis exemption for development affecting less than a small stated area of habitat with no priority habitat, householder development, self-build and custom-build within limits on dwellings and site area, development on a biodiversity gain site, and certain special categories. Exemptions must be claimed with evidence.
How does it work on a phased scheme?
An overall biodiversity gain plan for the whole site must be approved before the first phase begins, followed by a plan for each phase. Set the retained habitat out on a constraints plan at the start and treat it as undevelopable, because a later phase encroaching on it means buying offsite units at the end.
What if the site contains irreplaceable habitat?
The 10 per cent calculation does not apply to that habitat. The plan must instead include a statement of the bespoke compensation agreed with the authority. National policy resists the loss of irreplaceable habitat, so the planning permission itself is usually the harder step, and the compensation is negotiated rather than calculated.
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.