Carson just wrong.

Ben Carson just called his new plan a 'genuine flat tax.' He's wrong.

By Danny Vinik

On Monday, Ben Carson released his tax plan, which he calls a “genuine flat tax that treats all taxpayers fairly.”

A flat tax is considered the optimal tax system by many conservatives. It would eliminate the current seven tax brackets in favor of one rate for everyone. Flat tax supporters say it would be both fairer and would boost growth.

In calling his tax a “genuine” flat tax, Carson seemed to be distinguishing himself from other Republican candidates, like Sen. Marco Rubio (R-Fla.) and former Florida Governor Jeb Bush, who have proposed tax schemes “flatter” than the current U.S. tax code, but not actually flat; they still retain three tax brackets each.

Only one problem with Carson’s announcement: His tax isn’t actually flat either.

Carson would tax all income at a 14.9 percent rate—so far, so flat. But that rule wouldn’t apply to everyone: He would exempt all income below 150 percent of the federal poverty line. So for a family of four, that means their first $36,375 in income will go untaxed. Instead, they will pay a “de minimis tax payment,” although Carson does not provide any more information about what that payment would be or whether it would vary with income.

In other words, Carson’s plan doesn’t actually require all Americans to pay the same proportion of their income in taxes. So it’s not flat.

In fact, here’s what the average tax rate for a family of four would look like depending on their income level (excluding the “de minimis” tax).

Carson concludes his tax plan by saying that it does not “falsely claim to be a flat tax while still deriving the bulk of its revenues through higher business flat taxes that amount to a European-style value-added tax.”

That’s true—but it still does falsely claim to be a flat tax plan.

It’s also not something else Carson likes to talk about: tithing. Carson often suggests that the U.S. tax code should be based on the Judeo-Christian practice of tithing—everyone paying the same tax rate on all their income.

"When I say tithing, I am talking about the concept of proportionality," Carson said in November. "Everyone should pay the same proportion of what they make. You make $10 billion, you pay $1 billion. You make $10, you pay $1.”

So how would those people make out under Carson’s plan? If you make $10 billion, you’d pay about one and a half billion; if you make $10, you pay more like $0 (plus the unspecified “de minimis” tax). His plan is radical, but it’s actually less radical than he’s claiming, and less extreme a change to the law than “tithing” would be. And his misdirection only shows just how far our childhood definition of “fair,” and the easy-sounding solution of a “flat tax,” is from the real-world challenges of tax policy.