I am a foreign national and living in overseas. I was in USA from 1988 to 2001/2002 on F1 (student) and H1 (work visa) . I moved out of USA in 2001/2002. During that period I always worked and my previous employers withhold my Social Security and Medicare taxes.

I understand that I can get the refund for social security and Medicare taxes in a lump sump amount since I moved out of USA permanently and not eligible for benefits. How do I go about it? Thanks in advance.