<p>Is it just that internal auditors focus on non publicly traded companies, and that they don’t do taxes?</p>
<p>External auditors will almost without exception be CPAs or on the track to earning the CPA credential, but not all CPAs are external auditors. In fact, most who earn the CPA credential eventually end up doing something other than external audit.</p>
<p>External auditors are by definition not members of the entities that they audit. Their independence is central to their credibility.</p>
<p>Internal auditors often earn the CPA credential, though there are also specific professional credentials for internal auditors. However, no professional credential is required for internal auditors. Some are not even accounting specialists by training.</p>
<p>Internal auditors, again by definition, are members of the entities that they audit, though the function is frequently “outsourced” to specialty consultants. Their function depend on the needs of the entity. They can be corporate cops or they can be efficiency consultants, or some sort of hybrid. It used to be that internal audit was often a type of executive fast track training function, but that is much less common since the Sarbanes-Oxley Act and the importance of SOX 404 compliance. [Sarbanes?Oxley</a> Act - Wikipedia, the free encyclopedia](<a href=“http://en.wikipedia.org/wiki/Sarbanes–Oxley_Act]Sarbanes?Oxley”>Sarbanes–Oxley Act - Wikipedia)</p>
<p>Tax is typically a specialty and there are both internal and external business tax preparation or audit specialists as well as those who do individual taxes or individual tax audit. These people are often CPAs, but there are lots of non-CPAs involved in various aspects of tax.</p>
<p>There are many more categories of accountants and related professionals.</p>
<p>The CPA is a professional credential. It is legally required for a few purposes, but the vast majority of those holding the CPA credential don’t perform any of the functions for which it is required by law.</p>
<p>I see a lot of internal auditors in IT related to SOX who have zero financial knowledge. They are dealing with systems.</p>