Before you start: is your development exempt?
Not every development needs to deliver BNG. Before investing time and money in the compliance process, check whether your project falls under one of the current exemptions. Key exemptions include householder applications, developments impacting less than 25 sqm of habitat (rising to 0.2 hectares in late 2026), and permitted development rights.
Check in under a minute
Our free Exemption Checker walks you through the criteria with a simple decision tree. Answer a few questions, get a clear answer.
If your development is not exempt, you'll need to follow the BNG compliance process. Here's the full roadmap, phase by phase.
The compliance roadmap
Never clear a site before survey. If you clear habitats before the baseline assessment, the LPA may require you to demonstrate what was there before — using the pre-clearance value as the baseline. This almost always results in a much higher (and more expensive) BNG obligation than surveying the intact site. It can also lead to enforcement action.
The most common delay: Gain plan approval is the single biggest bottleneck in the BNG process. Many developers underestimate the time needed to finalise the plan, secure off-site allocations, and get LPA sign-off. Start preparing your gain plan as soon as planning permission is granted — don't leave it until you're ready to break ground.
Cost planning
BNG costs vary enormously depending on site size, ecological complexity, and the delivery route used. Here's a framework for budget planning:
| Cost element | Small site (1–9 units) | Major development (10+ units) | Notes |
|---|---|---|---|
| Ecology survey & metric | £1,500–£3,000 | £5,000–£15,000+ | Depends on site complexity, number of survey visits |
| On-site design integration | £1,000–£5,000 | £5,000–£30,000 | Landscape architecture and habitat design |
| Off-site units (if needed) | £20,000–£35,000 per unit | £20,000–£35,000 per unit | Market rate; varies by habitat type and location |
| Statutory credits (last resort) | £84,000+ per unit (with SRM) | £84,000+ per unit | 2x multiplier makes credits 2–4× more expensive than off-site units |
| Legal fees (S106/covenant) | £2,000–£5,000 | £5,000–£15,000 | For securing off-site gains |
| 30-year management | Variable | Variable | Factor into service charges or endowment |
| LPA monitoring fee | Set by LPA | Set by LPA | Payable if BNG secured by S106 |
Rule of thumb: For most developments, BNG compliance adds 1–3% to total project cost when on-site delivery is maximised. Costs escalate sharply if the site has high-distinctiveness habitats or if you resort to statutory credits. Early engagement with an ecologist is the single most effective way to control costs.
Top 10 developer tips
- Engage an ecologist before you buy the land. Understanding BNG costs at the acquisition stage prevents nasty surprises. A pre-purchase ecological appraisal costs a few hundred pounds and can save tens of thousands.
- Never clear the site before survey. This is the most expensive mistake in BNG. The LPA will use the pre-clearance value as your baseline.
- Design with BNG from day one. Integrating habitat into the site layout from the start is far cheaper than retrofitting it later.
- Understand your trading tier exposure. If your site has Medium or High distinctiveness habitats, you'll need to replace like-for-like. Check the trading rules.
- Check off-site availability early. Use our Postcode Lookup to see whether gain sites exist in your area. If not, you may need to look further afield — or face credit costs.
- Budget for BNG in your financial appraisal. Don't treat BNG as an afterthought — include the costs in your land purchase appraisal and development budget.
- Talk to your LPA early. Pre-application discussions about BNG can prevent delays and disagreements later.
- Start your gain plan immediately after planning permission. The gain plan is a pre-commencement condition. Delays here delay your start on site.
- Consider the 30-year management cost. On-site habitats need managing for three decades. Factor this into service charges or management company arrangements.
- Consider off-site units as a clean break. Some habitat bank operators fully fund 30-year management and absorb all liability, giving you a clean break with no ongoing obligations.
Common pitfalls
- Underestimating temporal discounting. Habitats that take decades to establish are heavily discounted in the metric. This creates much larger shortfalls than many developers expect.
- Forgetting hedgerows and watercourses. These require separate unit types that cannot be substituted with area habitats. Budget separately.
- Assuming all LPAs work the same way. BNG implementation varies significantly between authorities. What works in one LPA may not work in another.
- Leaving off-site sourcing to the last minute. In some areas, particularly the 202 LPAs with no registered habitat banks, finding local units takes time. Start early.
- Not considering Section 73 implications. If you vary your planning permission, previous credit purchases carry over — but the metric may need recalculating.
Managing multiple sites? For developers with portfolios across multiple LPAs, ectare.dev provides LPA-level analytics showing unit availability, supply gaps, and market conditions — helping you assess BNG costs and risks at scale. See which LPAs have registered habitat banks and where geographic gaps exist.