Employees are not eligible for health insurance premium tax credits under Obamacare if the employer provides a "mimimum value" of "affordable" coverage for employees. In REG-125398-12 the IRS proposes that the employer's share of the health insurance plan costs must be at least 60% in order to qualify for the "minimum value" safe harbor.
For an excellent summary and more details, go to this Journal of Accountancy article: http://www.journalofaccountancy.com/News/20137889.htm
To be continued....