Employers who reimburse employees on a pre-tax basis for premiums the employees pay on their own individual health insurance policies (whether under an Obamacare Exchange or otherwise) are at risk for a $100 per day per employee excise tax. This is according to a recent IRS Q&A.
There are those that assert such arrangements can be structured through Code §125 to avoid the excise tax.
Employers should tread carefully in this area.
IRA Q&A; See also Notice 2013-54