What is an Audit trail?
An audit trail is a chronological, tamper-resistant record of who or what did what, when and why in a system, used to review, investigate and prove how a decision was made.
In more detail
For automation, an audit trail records each run: the input received, the rules or model version applied, the output, any human approval with name and time, and the actions taken in other systems. It answers an auditor's question months later: why was this invoice paid? It also helps with debugging. Good trails are append-only, time-stamped, searchable and kept for the period your regulations or policy require. Capture the evidence along with the outcome: the document image, the extracted fields and the matched PO. Keep personal data in logs to a minimum. An agent whose actions you cannot reconstruct is not ready for finance.
Example
An invoice was paid by an automated run. The trail shows the PDF, the extracted fields with confidence scores, the PO and receipt it matched, the approver who accepted a 1 percent price variance and the payment batch ID.