I have searched everywhere and never got a definitive answer on this topic...
Thanks in advance...

my case:

- on F1 visa.
- student from aug 04 - aug 06 (graduated in aug 06)
- on opt sep 06 - sep 07
- working from nov 07


my questions:

- Do i have to pay SS/medicare for 06. If no do i have to exempt my days of presence as
days in school using 8843?
- For 07, although I will be on OPT, i cant exempt days as I will not be in school. so i will be
considered resident alien correct? do i have to pay SS/ medicare for 07?
- I have already filed taxes for 06. can i still file 8843 and 843 to get a refund from the IRS

You should NOT be paying Social Security or Medicare taxes while you are on a F-1 visa.

Your OPT time is considered an extension of your schooling, so you are still exempt from Social Security and Medicare taxes while on OPT.

You should have filed the Form 8843 with your tax return, which I assume was Form 1040NR or 1040NR-EZ. If you did not, fill it out, sign it and mail it to the same address you sent the tax retrun to in Austin, Texas.

Yes, you CAN file Form 843 to get a refund of Social Security and Medicare taxes. But, FIRST, ask for a refund from the employer.