Trading rules in the statutory biodiversity metric: where the workbook tests them and the flags it raises

The trading rules are Rule 1 of the statutory biodiversity metric. The user guide states them in one table, and GOV.UK is the place to read the rule itself. This page is about something else: what the calculation tool does with the rule. Which sheets and cells test it, in what order, the exact ▲ and ⚠ strings each test writes, what clears each one, and what the free Quadrat check reports when it reads the file. Every statement below was read from the formulas of the published workbooks named under Sources.

“The trading rules set minimum habitat creation and enhancement requirements to compensate for specific habitat losses, up to the point of no net loss. They are based on the habitat type and distinctiveness of the lost habitat.” — statutory biodiversity metric user guide, June 2026, p. 15

The guide adds that once the trading rules are met, the net gain itself can come from the creation or enhancement of any habitat within the same module (p. 17). The workbook tests exactly that: not whether the 10% is reached, which is a separate test, but whether every band of loss has been replaced by the right kind of unit first.

Two places, two tests

The statutory metric 1.0.4 tests the trading rules twice, and the two tests write different flags.

1. Row by row, on the enhancement sheets

On A-3 On-Site Habitat Enhancement and D-3 Off-Site Habitat Enhancement, every row is a baseline parcel that keeps its reference and gets a proposed habitat. The sheet copies the parcel's baseline habitat, its distinctiveness score and a column headed Required Action to Meet Trading Rules (column O) from the baseline sheet, where the workbook fills it from its habitat lookup for the baseline habitat type, or with Bespoke compensation likely to be required when the baseline row is marked irreplaceable. Column T then tests the proposed habitat against that required action, in this order:

• Same distinctiveness…: the row fails if the proposed habitat's distinctiveness score is below the baseline's.
• Same broad habitat…: the row fails if the proposed habitat is in a different broad habitat and has a lower distinctiveness score. A different broad habitat at the same or a higher band passes this test.
• Same habitat…: the row fails unless the proposed habitat is the baseline habitat.
• Bespoke…: the row fails unless the proposed habitat is the baseline habitat, with one exception the formula names, a baseline in Woodland and forest – Other.

Any of the four writes Error - Trading rules not satisfied ▲ in column T. If none of them fires but the proposed habitat's distinctiveness score is lower than the baseline's, the same cell writes Error Trading Down ▲. The watercourse enhancement sheets (C-3, F-3) carry the trading-down test in column O and not the required-action test; the hedgerow enhancement sheets carry neither. Creation rows on the -2 sheets have no row-level trading test at all: a created habitat is only ever judged in the summary below.

What clears it: read the required action on the row and change the proposed habitat until it satisfies it. Nothing else on the sheet clears the cell. The condition and strategic significance columns are not part of this test.

2. Project-wide, on the three Trading Summary sheets

Trading Summary Area Habitats, Trading Summary Hedgerows and Trading Summary WaterC's are automated: nothing is typed on them. Each opens with a table of distinctiveness bands, the rule the workbook applies to that band, in its own words, and a Trading Satisfied? cell that reads Yes ✓ or No ▲:

The band rules as written in cells C5–C9 of each summary sheet, metric 1.0.4. The ⚠ in the Very High row is part of the header text, not a flag.

Below the table, one block per band lists every habitat group (area) or habitat type (hedgerow, watercourse) with its on-site, off-site and project-wide unit change. The arithmetic the Trading Satisfied? cell reads, on the area sheet:

• Very High is satisfied when the band's unit losses sum to zero or more.
• High is satisfied when the band's Remaining losses; Like for like not satisfied figure is zero or more: each high-distinctiveness habitat group must be replaced within its own group.
• Medium is satisfied when the Medium Distinctiveness Unit deficit is zero or more, and that deficit is the medium losses still unmatched within their broad habitat plus the surplus units the Very High and High blocks have available. Units trade up, never down: a surplus of high-distinctiveness units can cover a medium loss, a medium surplus can never cover a high loss.
• Low is satisfied when the band's net change, plus any cumulative surplus left over from the medium band, is zero or more.

The hedgerow and watercourse sheets run the same shape over their own bands. Beside each habitat group a ▲ or ⚠ appears where that group's project-wide change is negative, and beside each band's summary figures a ⚠ means the band is short before surplus from a higher band is counted and a ▲ means it is still short after. These are the bare symbols the glossary lists as ▲ with no text and ⚠ with no text.

What clears it: open the summary the flag names and read down to the block whose balance is negative. That block names the habitat group, and the band rule above it says what may replace the loss: the same habitat, the same broad habitat, or anything of a higher band. Create or enhance there, on site or off site, until the block's figure is zero or more.

Where the verdict is echoed

The Headline Results sheet asks Trading rules satisfied? in B55 and answers in F55 by reading every band's Trading Satisfied? cell on all three summaries: one No ▲ anywhere and F55 reads No - Check Trading Summaries ▲. The same answer is repeated at the top of every data-entry sheet, in the summary cells above the parcel rows, as No - check trading summaries ▲ on the area sheets and No - check trading summary ▲ on the hedgerow and watercourse sheets. Headline Results B94, the master switch, then reads Input errors/rule breaks present in metric ▲ for as long as any ▲ exists anywhere. One more echo is specific to the top band: if the area or watercourse summary still shows a Very High loss unmatched, the Credits Summary sheet writes ERROR - This metric still includes losses of very high distinctiveness habitat…, because statutory credits cannot buy those units.

The user guide's troubleshooting table (Appendix, Table F, p. 89) covers this flag in one line: the error appears when the trading rules are not met, at the top of each habitat tab, in the trading summaries and in the headline results, and the action is to consult the relevant trading summary tab for why.

The small sites metric

The small sites metric 1.2.3 has no trading summary sheets. It tests the rules on each data-entry sheet, in the automated rows below the parcels:

• 5. Area Habitats, section 1e. Trading Summary: cell E108 reads Error - Trading Rules Not Satisfied - Insufficient Units Created Within Habitat Groups ▲ when any medium-band row of the 1f. Habitat trading assessment table below it answers No ▲: that table lists every broad habitat type with its baseline units, on-site provision and net change, and a medium row answers No when it had baseline units and its net change is negative (low rows are not tested there). Cell E109 reads Error - Trading Rules Not Satisfied - Insufficient Biodiversity Units Created ▲ when the medium-and-low band total is short. Either cell otherwise reads Trading Rules Satisfied ✓.
• 6. Hedges & Lines of Trees and 7. Watercourses: cell E97 reads Error - Trading Rules Not Satisfied ▲ on the same pattern.
• 8. Headline Results, D7, labelled Trading Rules: reads Trading Rules Not Satisfied ▲ if any of those four cells carries an error, else Trading Rules Satisfied ✓. D9's next-steps line then changes from Check for input errors/rule breaks present in the metric ⚠ to Scheme alterations or offsite units required.

What clears it: the 1f table names the broad habitat type in deficit; create or enhance within it until its net change is zero or more.

Every trading flag, in one list

What the free check does with them

Drop the metric on the check page and Quadrat reads every sheet except the lookup tables. Each trading flag on an enhancement sheet is listed with the parcel's reference, its habitat and its User comments cell beside it; each bare ▲ or ⚠ on a trading summary is listed by sheet and cell; the headline answer, F55 on the statutory metric or D7 on the small sites metric, is transcribed on the results line as Trading rules: …. Any ▲ makes the verdict Not ready. Quadrat copies the workbook's stored values and never recalculates them: it does not compute a unit, does not say which habitat would satisfy a required action, and does not apply Rule 4, the decision maker's permitted deviation, which is recorded on the Start page and is the authority's to accept.

Sources

The statutory biodiversity metric calculation tool 1.0.4 (macro-disabled workbook) and the small sites metric 1.2.3, both as published on GOV.UK's Statutory biodiversity metric tools and guides page and read on 2 October 2026: the cells named above are theirs, and the band rules are quoted from the summary sheets' own cells. The statutory biodiversity metric user guide, June 2026 edition, pp. 15–17 (Rule 1 and the notes on trading) and p. 89 (Table F). A later release of either workbook may move a cell or change a string; the version each statement rests on is named here so it can be checked. Quadrat is not affiliated with Defra or Natural England. If a cell on this page does not match the workbook in front of you, write to hello@quadrat.uk; replies are signed as Quadrat.