不需要在一定期限内enroll Medicare Part A，也就是说Part A什么时候加入都行，没有penalty

https://www.medicare.gov/Pubs/pdf/11036-Enrolling-Medicare-Part-A-Part-B.pdf

 

"What's a Part A late enrollment penalty?

If you get Part A for free, you won't have to pay a Part A late enrollment penalty if you decide to enroll after you first become eligible. "

除非没有资格享受免费Part A，也就是SS没交够年份的人。