Most people enroll with Medicare at the age of 65. This includes Part A for hospitals and part B for doctors.
If you don’t retire and you have group health insurance from your employer, or from your spouse’s employer, then you can legally delay enrolling in Part B. There will be no penalty as long as you have other coverage from employment.
There is a catch though. You can only delay enrolling in Part B under the above condition if your company employs at least 20 people. In that case, you must enroll in Medicare (both A and B). Also, your employer’s insurance is considered secondary since Medicare will pay claims first.
If you do work for a larger company and can delay enrollment as I mentioned above, then when you do eventually retire you’ll have eight months to enroll in Part B without penalty. This is known as a special enrollment period.