Q.Which of the following is the auditor's most effective method for detecting an 'error of complete omission' — a transaction that has never been entered anywhere in the client's books?

A complete omission leaves no trace inside the books at all, and a Trial Balance still agrees perfectly despite it — so the auditor must look OUTSIDE the books, at external evidence, to catch it.

Why (c) is correct: A complete omission means both the debit and credit aspects of a transaction are equally missing from the books — so re-casting ledger totals, re-balancing accounts, or checking Trial Balance agreement will all show everything is perfectly in order, because nothing internal is out of balance. The only way to catch it is to go outside the books entirely — comparing the client's records against independent external evidence (a supplier's invoice, a bank statement showing a receipt/payment the books don't reflect, correspondence referring to a transaction, or a physical stock count) that reveals a transaction genuinely occurred but was never recorded.

Why the distractors are wrong:

• (a) Re-checking casting/balancing only catches arithmetical mistakes WITHIN entries already made — it cannot reveal a transaction that was never entered at all.
• (b) and (d) both describe checking Trial Balance agreement, which — as covered in the previous section — a complete omission never disturbs in the first place, since both sides are equally absent.

A very common mistake is assuming that if the Trial Balance agrees, the books must be free of errors. Complete omission is the clearest counter-example: the Trial Balance can agree perfectly while a whole transaction is simply missing — only external verification, not internal arithmetic, can catch this.