That’s all good and fine about tax professionals, but I’ve found you’ll get different answers from different CPAs. Some are much more conservative than others when telling you what their interpretation of what you can deduct is. Some are way to conservative, some seem pretty fast and loose.
Some of it boils down to how much money we are talking about. They don’t have the resources to chase small change almost always.. Some ex wife might call them to report her ex is bragging about making $5000 selling a car and is sure he didn’t report it, and they’ll basically tell her to go away. They catch word some high earner made 100 grand selling a car and didn’t report the profit, and they’ll throw a bunch of resources at going after the guy.