Under the Patient Protection and Affordable Care Act (Obamacare), employers must provide notice to their current employees by October 1st. The Department of Labor has an extensive site discussing the various requirements. The details are explained in its Technical Release.
The law gives three requirements for the notice. First, it must provide information about the applicable health benefit exchange. The term exchange has been replaced to marketplace because it was causing too much confusion. In California, the health insurance marketplace is called Covered California. Second, it should explain that the employee may be eligible for a premium tax credit. Third, it must explain the disadvantages of buying insurance through the marketplace. Namely, it will not be subsidized by their employer and the premiums are not tax deductible.