Your auditor won't check every single invoice — and that's completely normal
Why does the auditor only pull a sample of my invoices instead of reviewing every one of them? Does that mean the final numbers aren't fully reliable?
ISA 530 permits the auditor to rely on a sample of transactions rather than the full population, because checking every single invoice and entry in a company with thousands of transactions isn't practical and wouldn't add real accuracy worth the time and cost. The purpose of an audit is to provide reasonable assurance that the financial statements are free of material misstatement, not an absolute 100% guarantee.
There are two types: statistical sampling, where the sample size and selection method are determined randomly based on predefined risk and materiality levels; and judgmental sampling, where the auditor selects specific items based on professional judgment — high-value transactions, unusual items, or anything carrying a higher risk indicator. Larger or riskier transactions usually get deeper scrutiny, not because they're suspicious, but because their impact on the financial statements would be greater if they contained an error. This is a globally recognized approach, and a core part of the audit methodology RASEEKH applies with its clients.