BNG metric update, 3 November 2026: what project teams should check

10 November update to the statutory metric calculator

Defra’s version history now records v1.1.1 of the statutory biodiversity metric calculation tool. It corrects a formula issue on the Offsite gain site summary tab. The v1.1.0 changes described below include increased entry capacity and associated workbook updates.

Before reissuing a workbook, confirm the applicable version for the project. Keep the previous file, record the version and recheck off-site entries, the summary and the results relied on by the project team. Where the outputs differ, ask the person responsible for the calculation to reconcile the changes before submission. Check the version history separately for the small sites tool.

Defra, Statutory biodiversity metric tools and guides, version history, updated 10 November 2026

What changed in the November BNG metric update?

Defra released statutory biodiversity metric version 1.1.0 on 3 November. Its data-entry tabs now provide 350 rows. The Offsite Summary and associated cell references accommodate that increase. The Irreplaceable Habitats tab also has 350 rows and an added macro.

Separately, the November user guide clarifies the spatial risk multiplier for watercourse units where the impact site crosses several waterbody catchments. These are the changes identified in the official version history. Earlier entries on the same page describe earlier releases.

For project teams, the first question is which of the November changes affects the work in hand. A larger workbook may help a complex assessment. However, a catchment clarification needs an ecological review of the relevant off-site calculations.

How the watercourse catchment clarification works

The impact site is the red-line area or, for an NSIP, its BNG boundary. Where that site crosses several catchments, the guide applies these spatial risk categories:

See table 9 and “Development covering multiple boundaries” on pages 39–40 of the November metric user guide. Area habitats and hedgerows use different geographical boundaries.

The NSIP guidance also encourages gains close to the actual impact, recognising each waterbody’s ecological characteristics. Therefore, an available multiplier score should inform the assessment alongside the ecological case for the proposed location.

Does an existing assessment need a new workbook?

GOV.UK continues to permit previously published versions of the statutory metric tools. The release does not, by itself, invalidate every existing calculation or require every project to start again. Download current files and check the version position on the official tools page.

Nevertheless, ask the assessor whether the clarified guidance affects your project’s assumptions. If the team chooses to transfer data, check the resulting workbook before relying on it. Keep the original issue identifiable and record the reason for the revision.

Also distinguish this technical release from the start of mandatory BNG for relevant NSIP applications on 2 November 2026. Our NSIP application and delivery checks cover that separate change.

Five checks before your next metric issue

1. Identify the files. Record the workbook version, issue date and current layout reference.
2. Map the boundary. For relevant watercourse calculations, identify the waterbody and operational catchments crossed.
3. Explain the choice. Ask the assessor to record the spatial risk category and supporting location evidence.
4. Compare the outputs. If transferring data, reconcile entries, totals, warnings and supporting documents before issue.
5. Connect the package. Use matching references in the habitat plan, metric, report and any off-site allocation evidence.

These are practical coordination checks. They help the project team identify questions for the appointed assessor; they do not replace the assessment. If documents disagree, use our habitat plan and metric reconciliation checklist.

For off-site delivery, also review the allocation evidence before the gain plan goes forward. A consistent issue set makes the assessment easier to review and reduces avoidable clarification requests.

Scope and sources

This article covers Defra’s 3 November 2026 metric release for England. The official change log, tools page, November user guide and NSIP guidance are linked above. The guide’s document-history entry is dated 2 November; the GOV.UK release was published on 3 November. Check the latest official documents when preparing a submission.