The US’s tax system is different from some other countries’, because citizens are responsible for disclosing all their taxable income to the government instead of the government telling them what they owe. The IRS calls this “voluntary compliance,” which implies that the 85% of taxpayers who obey tax laws do so of their own free will, out of a sense of duty or because it’s the right thing to do.

It’s the IRS’s good luck that many Americans still seem to believe an army of tax detectives lurks behind every door. In reality the agency has struggled to enforce the law. The chance that an average taxpayer will be audited in any given year is vanishingly small, around 0.4%. For a rough measure of how much tax evaders cost the Treasury, look at the size of the “tax gap.” That’s the difference between what the government is owed and what the IRS is able to collect—mostly a result of taxpayer error or dishonesty. The most recent estimate, from 2022, put the net tax gap at $606 billion.