Why do certain accounts have to be audited 100 Percent?

Answer 1

Businesses have a level of "materiality" which could alter either the value of the company's financial position or the company's earnings or loss. This level of materiality varies from situation to situation, but you might define it as what a reasonably prudent person would accept.

Certain accounts, because of their nature and value to the company, are material in and by themselves, but may not contain material transactions, in these instances the transactions are sampled to make sure that in total the auditor can rely on the account. An example of this might be a grocery store's sales, where maybe noone buys more than $200 daily, but the store sells $400,000 daily.

Other accounts represent transactions that in and by themselves are material to the company; these transactions will be audited completely. As an example, maybe a heavy equipment company sells $1,000,000 per month, but every contract is for $250,000; the auditor is going to want to look at every transaction. Other accounts are susceptible to fraud or criminal activity, these will be audited completely as well.

Answer 2

You need to be more specific. In most industries every account get audited. In some only certain accounts when they seem excessive or are related directly to taxation.