Research-group reviews of the plan have found that most families making $100,000 or less would pay thousands of dollars more each year.

“The larger point is that people don’t really understand what the 9-9-9 plan actually is, and they’re assuming incorrectly that they may not pay one or any of these taxes,” said Joe Rosenberg, a research associate for the Tax Policy Center, a group based in Washington, D.C., that bills itself as a nonpartisan economic research institute…

The Tax Policy Center estimates that the three taxes combined would be the equivalent of a 25.38 percent national sales tax. Because lower-income families spend a larger percentage of their income on tangible goods, they would be affected disproportionately.

The bottom line: A family with an income level of $40,000 to $50,000 would pay $3,407 more a year in taxes, while families making $500,000 to $1 million a year would pay on average $80,315 less, according to the Tax Policy Center.