Although the $120 billion payroll tax reduction offers nearly twice the tax savings of the credit it replaces, it will nonetheless lead to higher tax bills for individuals with incomes below $20,000 and families that make less than $40,000. That is because their payroll tax savings are less than the $400 or $800 they will lose from the Making Work Pay credit.

"It will come to a few dollars a week," said Roberton Williams, an analyst at the nonpartisan Tax Policy Center, "but it is an increase."