On Jan. 5, after it sunk in that Congress hadn’t reinstated the federal estate tax that lapsed on Dec. 31, Chicago lawyer Thomas Handler sent an e-mail to about 2,000 clients for whom his firm provides estate-planning services.

“This situation is a very real mess, which leaves millions of Americans unnecessarily at risk,” he said in the e-mail. “In the event that anyone does not wish to live with this current risk, a stop-gap provision can be put in place.”