Example
Dated source files and calculation versions help explain how a reported figure was produced.
The catch
A trail needs reliable records and access controls to remain useful.
In more depth
Audit trail, explained.
An audit trail lets someone outside the team rebuild a reported number from its raw evidence without asking the person who produced it. Verifiers test it in both directions. They pick a figure in the report and follow it down to invoices or meter readings, then pick a source record and check that it reached the total. Each step should show the emission factor used, the assumption applied and who approved any change.
A trail makes errors findable, though it cannot prove there are none. Carbon markets apply the same idea through a carbon registry, where serial numbers follow each credit from issuance to retirement.