The metric is not just a landscaping schedule
The statutory metric uses habitat information to measure biodiversity value and compare the existing site with the proposed outcome. Use the current government tool and its instructions. A Small Sites Metric is available for eligible development, but its eligibility and competency requirements must be checked rather than assuming any small application can use it. [5] [1]
Commission the baseline work before the layout is fixed. Give the assessor accurate site boundaries and ask them to identify retained, lost, enhanced and newly created habitat separately. Request both the completed calculation file and the plans needed to understand it, so a later revision can be checked properly.
Three documents with different jobs
The metric supplies the calculation. The biodiversity gain plan is submitted for the council's approval before commencement where the biodiversity gain condition applies. The habitat management and monitoring plan explains how the relevant habitat will be established, maintained and monitored over the required period. These documents should agree with each other but are not interchangeable. [2] [3]
For long-term habitat obligations, identify who will do the work, how success will be checked and how failures will be addressed. Ask the consultant to distinguish the planning submission service from any later monitoring visits or management responsibilities.
When can off-site units be used?
The delivery approach depends on the development and the applicable biodiversity gain hierarchy. From 6 August 2026, non-exempt minor development can consider onsite and off-site options together rather than first having to pursue onsite delivery. Statutory biodiversity credits remain a last resort; they are not the same product as privately supplied off-site units. [2]
Before buying units, ask the ecologist to establish the required habitat types and quantities and check the metric's trading and location rules. A seller's offer of a particular number of units is not, by itself, evidence that those units meet this development's shortfall. [1] [4]
Registration and allocation matter
Off-site gains must be legally secured and entered on the biodiversity gain sites register. Their allocation to the particular development must also be recorded before the council can approve the biodiversity gain plan. A purchase agreement alone does not complete that process. [4]
Ask the seller and advisers to make responsibilities explicit: who registers the site, who records the allocation, which development reference will be used and what happens if the agreed units cannot be supplied. Government guidance identifies these as matters to address in arranging the transaction. [4]
Budget for the whole obligation
Compare quotations on scope rather than an unsupported price per unit. Separate ecological assessment, legal work, the units themselves and any retained onsite management obligations. Keep the final metric, approved plan, allocation evidence and management commitments together in the project record.
Defra has announced further metric changes. The operative tool should be checked again before submission or purchase; an announced revision should not be substituted for the published statutory method. [6]