Medicare is secondary payer for people under age 65 who are entitled to Medicare because of disability and who are also covered under an employer's group health plan or the health plan of an employed family member. This includes disabled employees who are physically unable to be at work but are considered active because of continued eligibility for company benefits.

This secondary payer provision applies to group health plans of businesses that employ 100 or more people. Employees (and their dependents) of smaller companies may also be covered under certain conditions. Even if you are disabled, your employer or the employer of your spouse or any family member must give you the choice of accepting or rejecting the employer's health care plan as primary insurer.