As a result, families with an income near the median of $55,000 would owe about $2,700 less in taxes than if the Bush-era cuts had been allowed to expire.

A two-income couple earning $146,000 would owe about $7,000 less than if the tax cuts were allowed to expire, and about $3,400 less than they did in 2009.

The proposal does not include an extension of Mr. Obama’s signature tax cut, the Making Work Pay credit, which provided a credit of up to $400 for individuals and $800 for families of low and moderate income. Instead, the plan creates a one-year reduction in Social Security payroll taxes, which are generally levied on the first $106,800 of income. For an individual earning $110,000, that provision would reduce payroll taxes by $2,136.

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.”

To the wealthiest Americans, however, an assortment of breaks is available.

The plan includes a two-year “patch” for the alternative minimum tax, which is now paid by about 4 million taxpayers with income in the mid- to high six figures. Without the patch, more than 20 million additional taxpayers would have been liable for that tax.

The estate tax  which was allowed to lapse this year and was scheduled to resume at a rate of 55 percent on most assets above $1 million  will be reinstated under less onerous terms. Estates over $5 million will be subject to a 35 percent tax.