The IRS audited the tax returns of Darryl Blueberry, a former major league outfielder. It contended that, between $2013$ and $2016,$ Blueberry earned $$800,000$ for autograph signings, appearances, and product endorsements, but he reported only $$60,000$ of income. Blueberry attributed the shortfall to his receipt of cash for autograph sessions and promotional events. He allegedly concealed the cash payments in separate bank accounts of which his CPA was unaware. What tax compliance issues regarding the alleged underreporting are pertinent?