Most estates -- more than 99.5% -- don't. The federal government imposes estate tax at your death only if your taxable estate is worth more than $5.25 million for deaths in 2013 or $5.34 million for 2014 deaths. Assets left to a surviving spouse (as long as the spouse is a U.S. citizen) pass free of estate tax, no matter what the value. This rule became applicable to same-sex married couples in June 2013, when the U.S. Supreme Court struck down parts of the federal Defense of Marriage Act as unconstitutional. Assets left to a tax-exempt charity are also exempt from estate tax.