Normally, the IRS seeks to prove the requisite willfulness element by using indirect evidence rather than direct evidence—like the taxpayer’s admission or confession—since direct evidence is rarely obtainable. That said, the Supreme Court allowed the willfulness requirement to be inferred from “any conduct, the likely effect of which would be to mislead or to conceal.” Spies v. United States, 317 U.S. 492, 499 (1943).