How common evidence procedures differ in reliability, assertion support, and documentation value.
Audit evidence varies in persuasiveness. Observation, inquiry, inspection, and confirmation are all useful, but they do not provide the same strength of evidence or support the same assertions. The auditor chooses procedures based on the risk, assertion, source of evidence, and need for corroboration.
The AUD exam often asks which procedure is strongest for a specific assertion. The best answer usually identifies the evidence source and the weakness of the alternative procedures. Evidence obtained directly by the auditor from an independent external source is usually more persuasive than evidence generated internally by the client.
flowchart TD
A["Audit objective"] --> B{"What assertion is most at risk?"}
B --> C["Choose evidence procedure"]
C --> D["Consider source reliability"]
D --> E["Corroborate weak evidence"]
E --> F["Document conclusion"]
Reliability depends on source, form, and auditor control.
| Evidence feature | General reliability effect |
|---|---|
| External source independent of the client | More persuasive |
| Obtained directly by the auditor | More persuasive |
| Original document rather than copy | More persuasive |
| Written or electronic evidence rather than oral statement | More persuasive |
| Internally generated evidence with strong controls | More persuasive than the same evidence under weak controls |
| Inquiry alone | Usually least persuasive and needs corroboration |
These are general rules, not automatic conclusions. A forged external document is not reliable merely because it appears external, and an internal report may be useful if the auditor tests the controls over its preparation.
Observation means watching a process or control being performed. It is useful for procedures that occur at a point in time, such as observing inventory count procedures, cash counts, document handling, or the performance of a control.
Observation is strong for seeing what happened while the auditor watched. It is weaker for proving that the same control operated throughout the period.
| Observation supports | Limitation |
|---|---|
| Whether employees follow a procedure when observed | People may behave differently when watched |
| Whether a physical process exists | It does not prove consistent performance across the period |
| Whether count instructions are followed | It may need inspection, reperformance, or later testing |
For example, observing inventory count teams can support evidence about the count process and existence of inventory at the count date. It does not by itself prove valuation, ownership, or whether every count was performed properly before and after the auditor’s observation.
Inquiry means asking questions of management, employees, internal auditors, legal counsel, or third parties. Inquiry is important because it helps the auditor understand processes, identify risks, and interpret other evidence. It is rarely sufficient by itself.
Strong inquiry technique includes:
Inquiry is especially useful for identifying fraud risks, related parties, subsequent events, unusual transactions, and changes in controls. But because inquiry is a representation, it normally needs support from more persuasive evidence.
Inspection means examining records, documents, or tangible assets. It can support many assertions depending on the direction of testing.
| Inspection procedure | Direction | Assertion usually supported |
|---|---|---|
| Vouch recorded sales to shipping documents | From ledger to support | Occurrence |
| Trace shipping documents to recorded sales | From source documents to ledger | Completeness |
| Inspect fixed assets and match to the asset register | From ledger to asset | Existence |
| Inspect subsequent cash receipts for receivables | From later cash evidence to balance | Valuation and existence |
| Inspect board minutes and contracts | From records to obligations or disclosures | Completeness and presentation |
Inspection of tangible assets may prove that an asset exists, but not necessarily that the client owns it or that it is recorded at the correct amount. The auditor often combines inspection with title documents, invoices, depreciation schedules, or impairment evidence.
Confirmation is evidence obtained as a direct written response from an independent third party. It is often persuasive because the auditor controls the request and receives the response directly.
Common confirmation targets include:
| Confirmation target | Common assertion support |
|---|---|
| Banks | Cash existence, loan completeness, collateral, restrictions |
| Customers | Accounts receivable existence and rights |
| Attorneys | Litigation, claims, and assessments |
| Vendors | Payables completeness when statements or direct confirmations are used |
| Custodians or brokers | Investments existence and rights |
Positive confirmations request a response whether the third party agrees or disagrees. Negative confirmations request a response only if the third party disagrees. Negative confirmations provide less persuasive evidence and are appropriate only when risk is low, balances are small and numerous, and the auditor expects recipients to pay attention to the request.
Auditor control is essential. The auditor should select recipients, send the requests, maintain control of addresses or electronic channels, receive responses directly, and perform alternative procedures for nonresponses to positive confirmations.
The strongest procedure depends on the assertion.
| Audit objective | Stronger procedure | Why |
|---|---|---|
| Verify cash balance | Bank confirmation plus bank reconciliation testing | External evidence obtained directly by the auditor |
| Test inventory existence | Observation and test counts | Direct evidence at the count date |
| Test inventory valuation | Inspect cost records, turnover, subsequent sales, and write-down analysis | Existence does not prove valuation |
| Test receivables existence | Customer confirmations | External evidence about recorded balances |
| Test unrecorded payables | Search subsequent disbursements and inspect unmatched receiving reports | Completeness requires looking outside recorded payables |
| Understand fraud risk | Inquiry plus corroborating documents and analytical evidence | Inquiry identifies leads but rarely proves conclusions |
The direction of testing matters. Vouching from the ledger to support is stronger for existence or occurrence. Tracing from source documents to the ledger is stronger for completeness.
Do not treat inquiry as sufficient persuasive evidence by itself. It is useful, but usually needs corroboration.
Do not treat observation as proof that a control operated all year. Observation is limited to the time observed unless combined with other evidence.
Do not assume confirmation proves every assertion. A customer confirmation may support existence of receivables, but collectability still requires valuation procedures.
Do not let the client control confirmations. Client involvement in sending or receiving responses weakens reliability.