I did a lot of research on this and thought I would share what I found out. If you are still working when you turn 65 and have employer insurance and work for a company that has more than 20 employees you can keep the employer insurance and completely skip medicare without penalty later. When you finally retire and go on medicare there is a form that the employer has to fill out stating that you were covered by insurance for all the years you didn't sign up for medicare. Then once you sign up for medicare you will also have to get a part D prescript
ion plan as well as a supplement that will cover what medicare parts A & B don't pay.
Note: if you start collecting social security while you are still working you MUST enroll in Part A whether you have employer insurance or not. Part A is the free part. I think you can still delay Part B as long as you are still working and have employer insurance. I didn't check into this too much yet because I plan to delay SS until I am at least 67 .. might hold off until 70 if I am still working.
I called the state Medicare help line, my local medicare help line and Medicare directly. I found the local the most helpful and had the least confidence with the direct Medicare (the woman just read what is on the website). The local site really explained in detail and said when I was ready to sign up to call them because they have a broker that can help me with the supplement policies.
https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/working-past-65