This applies to all employers, regardless of size, and applies to all employees including seasonal, part-time or full time.
According to Pat Wolff, health care specialist with the American Farm Bureau Federation, employers must distribute a form that tells employees whether or not they have health care coverage and includes information about the state exchanges so that they know where to go to purchase health insurance.
Wolff says employers must distribute the form even if no health care coverage is provided.
AFBF has provided a fact sheet for employers, and a copy of the form for employees (which requires information from the employer.)
You can also learn more from the Department of Labor.