From Fraud Red Flags to Defensible Evidence
A disciplined method for moving from anomaly to substantiated findings
A red flag is a question, not a conclusion
Unusual payments, duplicate addresses, unexplained overrides, and transactions outside normal operating hours can signal control weaknesses or potential misconduct. They can also have legitimate explanations. The investigator’s responsibility is to convert a preliminary signal into a testable question, not to treat an alert as proof. Premature accusations can damage reputations, compromise cooperation, and weaken a later legal or regulatory process.
The quality of an investigation is determined less by how many anomalies are found than by whether relevant evidence is preserved, independently corroborated, and evaluated against alternative explanations. A persuasive narrative unsupported by reliable records remains a weak finding.
Preserve first, analyze second
Once an allegation or high-risk indicator warrants inquiry, define the scope, identify custodians and systems, and coordinate preservation with legal counsel and qualified technical personnel as appropriate. Consider email, messaging platforms, accounting systems, access logs, contracts, banking records, and paper files. Record who collected each item, when, how, and from what source; maintain originals and work from controlled copies when feasible.
Preservation should be proportionate and legally authorized. An investigator should not assume unrestricted access to private devices or communications. The collection plan must address confidentiality, privilege, retention requirements, and the risk of altering metadata or overwriting records.
Follow the transaction and the authorization
Financial reconstruction begins by tracing a transaction from initiation to approval, posting, disbursement, and ultimate beneficiary. Compare purchase orders, receiving records, vendor-master changes, invoices, general-ledger entries, bank details, and exception logs. Reconcile amounts and dates across systems rather than accepting a single report as definitive.
For a suspected fictitious vendor, the existence of a shared mailing address or bank account is only a lead. Investigators should test the legitimacy of services, confirm counterparties independently, examine employee access and approval activity, and establish whether payments reached an unauthorized beneficiary. Evidence that does not support the initial theory must also be retained and assessed.
Corroboration and interviews
Documentary and transactional evidence should inform interviews, but interviews are not a substitute for corroboration. Begin with individuals who can explain processes and records, then address discrepancies with persons who have direct knowledge. Preserve exact material statements and distinguish what a witness observed from what the witness believes.
Corroboration becomes stronger when independently maintained sources converge: an approval log, a bank record, and a contemporaneous communication may each address a different element of the event. Yet apparent convergence can be misleading if all sources ultimately derive from the same inaccurate input. Investigators must understand provenance.
| Red flag | Evidence to seek | Critical caution |
|---|---|---|
| Duplicate vendor bank account | Master-file history, bank verification, ownership records | Shared accounts may have legitimate explanations |
| After-hours approval | System logs, authority matrix, work context | Timing alone does not establish intent |
| Invoice without receiving evidence | PO, receiving, contract, delivery confirmation | Service arrangements may differ from goods |
| Unusual journal entry | Entry support, approvals, subsequent reversals | Adjustments may be legitimate |
| Conflicting interview accounts | Contemporaneous messages and records | Inconsistency is not proof of dishonesty |
Findings that can withstand challenge
An effective report sets out the allegation, procedures performed, evidence relied upon, findings, limitations, and recommended control actions. It identifies the financial exposure using clearly stated assumptions and distinguishes known loss from estimated potential loss. The report should describe unresolved gaps without obscuring them behind confident language.
Where management may be implicated, independence and escalation arrangements require particular care. The organization should have a defined route to appropriate oversight—potentially the Audit Committee—so that those responsible for a questioned activity do not control the investigation’s scope or conclusions.
Professional references
- ACFE, Occupational Fraud 2024: A Report to the Nations.
- COSO and ACFE, Fraud Risk Management Guide, Second Edition (2023).
- The Institute of Internal Auditors, Global Internal Audit Standards (effective 2025).