What are tests of details?
We have reviewed files where the team ran 60 confirmation requests, received replies, filed them neatly, and still missed the misstatement. The confirmations tested existence, but the risk was completeness. Direction matters more than volume, and getting it wrong turns a real procedure into a tick box exercise.
Tests of details are one of two categories of substantive procedure (the other being substantive analytical procedures). They examine individual transactions and account balances to detect material misstatements directly, without relying on the operating effectiveness of the client's internal controls.
ISA 330.18 makes one thing non-negotiable: every material class of transactions and every account balance receives substantive procedures. For significant risks, ISA 330.21 goes further and requires those procedures to be specifically responsive to the identified risk. Tests of details are how you meet that requirement at the individual-item level.
Design starts with the assertion. If you are testing the existence of receivables, you select from the recorded balance and confirm or vouch back to source documents. If you are testing completeness of payables, you work in the opposite direction: from source documents (goods received notes, supplier statements) into the recorded balance. ISA 500 .A14 sets out this directional logic. Getting the direction wrong means the test does not address the assertion it was designed for.
ISA 500.6 defines what counts as sufficient appropriate audit evidence. "Sufficient" is about quantity (enough items tested). "Appropriate" is about relevance (does the evidence address the assertion?) and reliability (is the source credible?). A test that examines 60 invoices but checks only amounts, not counterparties, may be sufficient in volume and completely miss the occurrence assertion.
Key Points
- Tests of details detect misstatements by examining individual items, not by evaluating whether controls worked.
- ISA 330.18 requires substantive procedures for every material account balance and class of transactions, regardless of assessed risk.
- Selecting the wrong population or testing the wrong direction is the fastest route to an ineffective test. ISA 500 .A14 establishes the directional logic.
- External confirmations and vouching are among the most common forms; the choice depends on the assertion.
Why it matters in practice
Worked example: Krüger Maschinenbau GmbH
Client: German precision engineering firm, FY2024, revenue €120M, HGB reporter. Krüger reports trade receivables of €18.4M at year-end. The engagement team identified a significant risk of overstatement because Krüger sells bespoke machinery on long payment terms (90–180 days), and two customers in the automotive sector reported financial difficulty during Q4.
Selecting the assertion and designing the test
Existence is the primary assertion here. Under ISA 505.7 , the team designed a positive confirmation procedure targeting the 15 largest receivable balances (representing €12.1M of the €18.4M total) plus a random sample of 20 balances from the remaining population.
Sending confirmations and evaluating responses
14 of 15 large-balance confirmations returned with no exceptions. One customer (€1.8M) reported a disputed amount of €340K relating to a late delivery penalty. That customer confirmed €1.46M, not the €1.8M recorded. Of the random sample, 18 returned agreed and one did not respond. One reported a €12K timing difference.
Alternative procedures for non-responses
For the non-responding debtor (balance €45K), the team inspected the underlying sales invoice and dispatch documentation, then traced the subsequent cash receipt of €45K received on 14 January 2025. Existence confirmed.
Evaluating the results
Further investigation was needed on the €340K dispute. Krüger had not recorded a provision for the penalty, so the team concluded Krüger should recognise a provision of €340K under HGB §249(1). As for the €12K timing difference, it was a cutoff error that the client corrected. This is the kind of finding that generates the most review notes: a confirmation came back with an exception, and the team needs to chase it through to a conclusion rather than leaving it open on the schedule.
Key standard references
- ISA 330.18 requires substantive procedures for each material class of transactions and account balance.
- ISA 330.21 requires substantive procedures specifically responsive to significant risks. Tests of details are ordinarily more responsive ( ISA 330 .A52).
- ISA 500.6 defines sufficient appropriate audit evidence, covering sufficiency (quantity) and appropriateness (relevance and reliability).
- ISA 500 .A14 establishes directional testing logic. Selecting from the balance tests existence. Selecting from source documents tests completeness.
- ISA 505.7 governs the design and evaluation of external confirmation procedures.
Related terms
Related reading
Frequently asked questions
Are tests of details mandatory on every audit?
Yes. ISA 330.18 requires substantive procedures for every material class of transactions and account balance. For significant risks, ISA 330.21 requires tests of details specifically.
What is directional testing?
Selecting from the recorded balance tests existence/occurrence. Selecting from source documents tests completeness. ISA 500.A14 establishes this logic. Getting the direction wrong means the test doesn't address the intended assertion.