The “base” of our federal tax system is “income.” And that base functions by capturing the amount of “income” an individual or business earns over the course of a year, then subtracting various deductions, credits, and exemptions from that income, and, finally, applying the applicable rate of tax to the remaining income in order to assess the correct income-tax liability.

The concept might seem simple enough at first glance, but at least three factors make the system massively complex. The first is that the federal tax code consists of more than 4 million words seeking to define and apply the various …