The federal estate tax is gone for 2010. But estate planners and political scientists say a crop of uncertainties and unintended consequences have sprung up in its place.

In a move that surprised longtime lobbyists and observers, the U.S. Senate let the federal estate tax — the tax levied on wealth passed on to heirs — lapse on Jan. 1, after failing to compromise around a bill approved by the House of Representatives.

In 2001, President George W. Bush singed a law that lowered the estate tax to 45 percent with a $3.5 million exemption in 2009 and completely repealed the tax for 2010 before it sprang back to 2000 levels — 55 percent with a $1 million exemption — in 2011. But nobody expected Congress to let the 2010 repeal stick.

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