Audit Technique Guides are IRS guidebooks that give detailed insight into various industries IRS auditors may encounter. The guidebooks are written for IRS auditors but are useful for tax pros and business owners too, because the guidebooks provide insight into how the IRS believes tax law applies to different industries.
You can find the full list of ATGs on this page of the IRS website.
The industries covered range from daycare providers to attorneys to the wine industry to the aerospace industry. These guides make for fascinating reading for tax nerds. The key thing to remember when reading an ATG is that this is the IRS’s viewpoint on how tax law applies. If a tax pro is trying to construct a defense for their client, or figure out whether a deduction can be taken, etc., one also needs to consult court cases and review the regulations yourself. But the ATGs are a good, solid resource for typical situations that arise.
For more tax terms with simplified definitions, check out the Glossary page.