The IRS enforces this byzantine web of laws and loopholes by auditing people to check if their tax returns match what they actually owe. Thanks to movies, most of us probably picture an IRS audit as a small army of men in suits methodically combing through the records of the ultra-rich. But unfortunately, that's not accurate. The IRS actually audits poor people significantly more than the rich. For example, the most audited county is Humphreys, Mississippi, where more than a third of the population lives below the poverty line. It's audited 51% more than Loudon County, Virginia, which has the highest median income in the country.
On the surface, that doesn't make sense. Surely the IRS should focus their attention on the Jeff Bezoses of the world, given that their tax returns affect the national budget quite a bit more than, say, a struggling comedy writer's. But as it turns out, it's a hell of a lot easier to check for mistakes on a tax return for somebody who makes $20,000 a year than for somebody who makes seven figures. That sort of work can be done by a low-level employee and mostly via mail, whereas auditing the rich requires highly experienced senior auditors working countless hours.
The IRS claims they don't have the budget or time to go after the rich, so they primarily focus their efforts on checking for small discrepancies amongst the poor instead. The modern IRS mostly strives to hold single mothers accountable while allowing many rich people to straight up just not pay taxes. And why doesn't the IRS have more resources, you ask? Because Republicans have been cutting their funding for years. In fact, the IRS plans to eliminate another 2,200 jobs in 2020 to keep in line with budget cuts proposed by the Trump administration, which as we all know is run by a professional rich person. What a strange coincidence!