36.2 Evidence Reliability Drill

Drill Goal

Evidence questions on AUD often sound easy because the answer choices all look like audit procedures. The exam is really testing whether you can judge sufficient appropriate audit evidence, the standard set by AU-C 500. Sufficiency is the measure of quantity. Appropriateness is the measure of quality, and quality depends on two pillars: relevance to the assertion and reliability of the source or method. A large file of irrelevant evidence is not persuasive. A highly reliable document that tests the wrong assertion is also not persuasive.

The interrelationship matters: the higher the assessed risk, the more evidence may be needed, and the lower the quality, the more quantity is required to compensate.

Reliability Ranking

The AU-C 500 reliability generalizations are: external is more reliable than internal; internal is more reliable when controls are effective; auditor-obtained directly beats indirect; documentary beats oral; and originals beat photocopies, faxes, or scans. The hierarchy is not mechanical, though. A bank confirmation is strong evidence of cash existence but may not surface every restriction or compensating balance unless the form requests it. A customer confirmation supports receivable existence, but collectability is a valuation question needing subsequent cash receipts, aging, credit history, or allowance analysis.

Scenario Drill 1: Client-Downloaded Bank Statement

The staff accountant gives the auditor a PDF bank statement downloaded from the bank portal that agrees to the general ledger. The PDF is external in origin but has been routed through the client, which lowers reliability because it could be incomplete, altered, or not from the actual account. A stronger procedure is to receive a bank confirmation directly from the bank or obtain read-only portal access under auditor control, then reconcile confirmed balances to the ledger. If the client PDF is used, corroborate it rather than treat it as the best evidence.

Scenario Drill 2: Receivable Confirmation

The auditor sends positive confirmations to ten customers. Seven respond and agree; three do not. Management says the three are long-time customers who always pay. For the seven direct replies, evidence of existence is reliable. For the three nonresponses, management inquiry is not enough; the auditor performs alternative procedures such as inspecting subsequent cash receipts, shipping documents, sales orders, and invoices. Note that a negative confirmation provides weaker evidence than a positive one because no response is assumed to be agreement. If valuation is the concern, the auditor must also gather collectability evidence.

Scenario Drill 3: Inventory Observation

The auditor observes the client's count, independently test-counts selected items, and later traces test counts to the final compilation. Observation gives evidence about how the count was performed, and independent test counts provide direct evidence about existence. Tracing to the compilation tests whether observed quantities were included accurately. However, observation does not establish valuation: slow-moving goods, damage, and net realizable value require reviewing aging reports, sales after year-end, and write-down policies.

Scenario Drill 4: Management Representation Letter

Management signs a representation that all related-party transactions are disclosed, yet the team knows the CEO owns a separate logistics company the client uses. The management representation letter is required by AU-C 580 and dated the same date as the auditor's report, but it is not enough when a specific related-party risk exists. Stronger corroboration includes inspecting board minutes, vendor master data, conflict-of-interest questionnaires, contracts, payment records, and public filings to evaluate authorization, accounting, and disclosure.

Workbook Procedure Check

Use this four-question filter before choosing evidence:

1. Is the evidence relevant to the assertion named in the question?
2. Did the auditor obtain it directly, or did it pass through the client?
3. If it is internal, are the controls over the report effective and tested?
4. Does the procedure need a second source to corroborate inquiry, analytics, or management representation?

Practice Ranking

Rank these for evidence of revenue occurrence, strongest to weakest: a customer confirmation received directly by the auditor, a sales invoice prepared by the client, a management statement that the customer is real, and a shipping record from an independent carrier inspected by the auditor. A defensible ranking places the direct customer confirmation and the independent carrier record at the top, then the internal invoice, then inquiry. If the assertion shifts to cutoff, the carrier shipping record can become more relevant than the confirmation because it shows when control likely transferred.

The lesson the exam keeps testing is that the same document can be strong or weak evidence depending entirely on which assertion the question names, so always read the assertion first and rank the evidence against it rather than against a fixed mental hierarchy.