If you are working for an employer of 20 employees or over, you do not need to sign up for Part B (outpatient) services. Unlike Part A (hospital benefits), there is a premium for Part B. That premium is based on your adjusted gross income filed with your tax return. Also, please remember that Part B is not supplement coverage. Part A and Part B do have copays and Part B will not cover Part A’s copays.
If you work for an employer of 20 employees or more, you can delay your Part B with no penalty until you are ready to leave your employer insurance plan and fully go onto Medicare and one of it options (i.e. a Medicare supplement/medigap policy with a stand alone drug plan /or/ a Medicare Advantage/HMO plan /or/ an Employer Retiree plan).