I understand Part A is free, it covers the hospital. I am wondering about Part B. I honestly don't think I will need Part B for another 5 years, i don't go to the doctor very much, it would be cheaper to pay out of pocket. I don't do the annual tests because I don't agree they are needed. If I wanted to wait until I am 70 years old to sign up for Part B, would I have to pay for the amount I didn't pay since I was 65 years old?