Cain And Perry

Under the Cain and Perry plans, the family would face tax increases, with Cain charging $8,910 and Perry imposing an $8,200 tax.

Cain's 9-9-9 plan would shift the U.S. from an income tax system and toward a consumption tax system. The analysis for all families considers only the income tax changes under Cain's plan. The business tax, the sales tax and the elimination of the payroll tax would have disparate effects on the families and on wages and prices.

Under Romney's and Huntsman's plans, this family would receive a tax cut. Romney's plan to exempt investment income for most households would result in a $300 tax cut, and Huntsman's lower rates produce an $851 tax cut. The effects of Romney's plan could change depending on how he addresses tax credits for education that were expanded in the 2009 stimulus law and are slated to expire at the end of 2012.

Low-Income Family

Like almost half of U.S. households, the low-income family in the study pays no federal income taxes. Instead, it receives a refund of $2,383 under the current code because of the earned income tax credit, education credits and the child tax credit.

This family earns $30,000 a year in wages plus another $10,000 in disability pay from Social Security, most of which isn't taxed.

The family's future tax bills will turn on how the candidates would treat these refundable credits. Proposals that eliminate those features of the code could cause these families to lose their refunds, and instead pay no tax or some tax.

"To the extent those are lessened or taken away, it's debatable whether you call it a tax increase," Zelenak said. "It's nevertheless harming them in the bottom line and they need to look out for that."

For example, the $12,500 per-person exemption in Perry's flat-tax plan would prevent a low-income family from paying income taxes. Because Perry eliminates refundable credits, this family would take advantage of the option his plan provides to file under the current system. Even if the Bush-era tax cuts expire, the family would receive an $862 refund.

'Simplify Things'

"It looks initially that that should simplify things," Pickering said. "In the onset, it will double the work before it actually simplifies anything."