Senate Democrats are seeking to set the top tax rate on dividends at 23.8 percent, almost 20 percentage points lower than the proposal offered by President Barack Obama in his budget.

That detail, along with a top estate tax rate of 45 percent and a one-year patch to prevent the alternative minimum tax from affecting millions more families, are part of the written version of Senate Democrats' attempt to extend expiring income tax cuts for one year. The core of the proposal would extend the George W. Bush-era cuts through 2013 for 98 percent of households while letting them expire on income above $200,000 for individuals and above $250,000 for married couples.

A Senate Democratic aide, who spoke on condition of anonymity, confirmed the details. Senate Majority Leader Harry Reid, a Nevada Democrat, said last week that the Senate will vote before the August recess.