Only 44% of companies have taken steps to comply with new mandates from the Affordable Care Act that take effect in 2014 and later years, according to a survey of more than 4,000 employers by HR consulting company Mercer. Most companies say they were waiting for the Supreme Court's decision before developing strategies to deal with the law's 2014 provisions.

Now that the Supreme Court has upheld most of the law, 40% of companies say they will start taking steps to comply, while 16% plan to wait until after the November elections.

Looking ahead to the requirements they'll be facing in coming years, 28% of companies say the mandate that they provide coverage for those who work an average of 30 hours or more a week poses a significant challenge, while 29% are concerned about the auto-enrollment requirement. And 47% say they're worried about the tax on high-value health plans that will go into effect in 2018.