Have you ever wondered what an auditor looks for? Or how they look for it? The IRS has a website devoted to how they audit different industries. These are, admittedly, a deep dive. However, it may be worth searching your specific industry to see how auditors would approach an audit of your company.
Check it out here:
https://www.irs.gov/Businesses/Small-Businesses-&-Self-Employed/Audit-Techniques-Guides-ATGs