Less reported is the existence of dormant state estate taxes, ready to return on January 1, 2013 as the federal estate tax reverts to pre-2001 law. Under pre-2001 federal law, any amounts paid under a state estate tax were fully credited against federal estate tax liability; it was essentially free money for states that set up an estate tax, money that would otherwise go to the feds. This “pick up tax” or “sponge tax” structure was changed in 2001-05 to be a deduction, ending the free ride for states.
Source: Tax Foundation; Tax Policy Center; Federation of Tax Administrators.