Apple already doesn't pay its full share of U.S. taxes, said , a decentralized liberal group formed earlier this year. The company is also a leading voice in the WinAmerica campaign, an effort to return US$1 trillion in earnings by U.S. companies back to the U.S. at a 5 percent tax rate, instead of the normal 35 percent for repatriated earnings.

US Uncut has targeted several U.S. companies for its scorn. "Our rallying cry is, 'we all pay our taxes, and why don't they?'" said Ryan Clayton, a co-founder of US Uncut. "At the same time as we're firing firefighters, teachers and cops, it's just really irresponsible for them to not be paying their fair share of the public burden."

In its fiscal year 2010, ending in September, Apple reported income of $18.5 billion and paid $2.7 billion in income taxes, or about 15 percent.

Apple is not alone. Many U.S. companies report a large percentage of their income as earned overseas, and take advantage of other tax breaks, to reduce their tax rate from the full 35 percent in the U.S., said Mike Lunardoni, tax director with WTP Advisors, a tax advisory firm in White Plains, New York.

US Uncut is focusing recently on Apple, with protests planned outside the vendor's stores Saturday, because of its leadership in WinAmerica, Clayton said. "If [Apple] is going to be the tip of the sword for tax cheaters, then they're going to be the first on our target list," he said. "Engaging in this deceitful, shameful campaign is really sad, because most the time, Apple is a great company that operates in a socially responsible manner."