I agree that small companies would most likely hire an outside contractor to perform an audit if they do not have the resources to do their own internal audit. However, sometimes even larger companies hire independent contractors to perform audits, the reason being that having an outsider looking at your documentation, you are much more likely to catch something than if someone from the company is performing the audit. It is good to get an external perspective on your procedures and documentations. Also, many times these audit contractors are ex-FDA auditors or very familiar with what FDA would be looking for in an audit, so it really helps a company prepare for an FDA audit.