"What is the policy difference that the administration has suddenly found between qualified dividends and capital gains?" he said. "Why do they get different rates now?"

'Buffett Rule'

The administration also wants to impose a 30 percent minimum tax for individuals with annual income of at least $1 million, known as the "Buffett rule" after billionaire investor Warren Buffett, who originated the idea last year.

That would replace the alternative minimum tax, "which now burdens middle-class Americans rather than stopping the richest Americans from paying too little as was originally intended," the administration said.

Buffett, in a New York Times opinion piece in August, said that in 2010 he paid a lower tax rate -- 17.4 percent -- than "any of the other four people in our office."

The budget proposal doesn't say how much revenue the Buffett rule would generate and it doesn't provide details on how the rule would affect individuals' tax calculations. The U.S. collected $39.1 billion from the alternative minimum tax in 2011, according to projections from the Tax Policy Center, a nonpartisan research organization in Washington.

The AMT, in its current form since 1986, requires taxpayers to compare their tax liability under the regular tax code with their liability under the alternative minimum regime. Because the AMT doesn't allow the full benefits of state and local tax deductions or personal exemptions, people with large families or who live in high-tax states tend to be disproportionately affected.

The exemption levels aren't permanently indexed for inflation so, unless Congress acts to blunt its spread, millions more taxpayers will pay the alternative tax next year. If Congress doesn't act, the number of people paying the AMT will jump from 4.3 million to 31.2 million, according to the Tax Policy Center.

Obama's budget revives calls to allow the 2001 and 2003 tax cuts on income and capital gains to expire at the end of 2012 for families earning more than $250,000 a year and cap itemized deductions and other tax benefits for these families at 28 percent.

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