The IRS audited the tax returns of Darryl Strawberry, a former major league outfielder. It contended that, between 1986 and 1990, Strawberry earned $422,250 for autograph signings, appearances, and product endorsements, but he reported only $59,685 of income. Strawberry 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?