Hi

I am a resident alien for tax purposes (substantial presence test). My post-completion OPT began in September, '07 and have been employed ever since, as a postdoc in a US University. My employer withheld social security and Medicare from my March salary (but never before).

1. I read that if a person is on F1, that person is exempt from these taxes. To what extent is this true?

2. Do I have to pay the previous months' taxes now?

If yes, I should file a correction for my 2007 tax return, including the fact that I paid social security and medicare, right?

Thanks in advance.

1) Yes, you were exempt while on OPT. You need to ask for a refund of those taxes and, failing that, submit Form 843 to the IRS for a refund.

2) No.

The Social Security and Medicare tax issue is NOT linked to your 2007 return.

However, to claim the refund, you MUST file for 2007 as a non-resident alien (which is the CORRECT way for you to have filed), filing Form 1040NR or 1040NR-EZ.

If you filed Form 1040, you CANNOT claim the Form 843 refund.

So you may need to amend your 2007 return, filing Form 1040X with a properly-prepared Form 1040NR-EZ attached.

If you need professional help doing this, PM me.