Some people do not take Part B during their Initial Enrollment Period (IEP) because they or their spouse are still working and they have primary insurance from a current employer. You should talk to your employer when you become eligible for Medicare to see how your employer insurance will work with Medicare.
Your Initial Enrollment Period begins three months before your 65th birthday and ends three months after your 65th birthday. If you or your spouse are still working and you receive health insurance from that current employer, the insurance is primary if there are 20 or more employees at the company where you or your spouse work.
If you are already collecting Social Security you will be automatically enrolled in both Medicare Part A and Part B. If you are thinking about turning down Part B, you should call the Social Security Administration at 800-772-1213 and ask if you can do so without any penalties. When you call Social Security, it is important to write down whom you spoke to, when you spoke to them and what they said.