Hi,
I was on OPT from Jan 2008 to June 2008 and then on H1B from Oct 2008 -Dec 2008.
My husband has been on H1B for over 6 years and is considered a resident alien.
Since I was on OPT I did not pay Social security and medicare taxes from Jan-Oct 2008, only from Oct - Dec 2008.
My question is : Should I file jointly with my husband ? Or should I file single ? Which would be a better option ? Which forms should I fill?
Please advise
Thanks!

Sorry, I just noticed a mistake on my question, from Oct 2008 -Dec 2008 I was not on H1B, I was working using the employment authorization card obtained from my pending 485 Application to Register Permanent Residence. I am not sure if it does make a difference but just wanted to clarify.

If you elect to file jointly with your husband you will be treated as a resident for the entire year and you will need to pay social security taxes for the entire year. You need to determine how much social security tax would be due if you file jointly and compare that with the tax savings of filing jointly. If the cost of social security exceeds savings of filing jointly, then don't file jointly.

This is confusing... From what I read previously I thought I could file with my husband jointly as a resident and still be treated as a nonresident alien for the purpose of withholding Social Security and Medicare tax.
Please confirm.
Thanks!

No. If you file jointly with your husband, you owe social security tax.

IntlTax:

Your post from 28 Feb 09 is not correct. The IRS still allows the non-resident alien spouse to be exempted from FICA taxes even if they file jointly with their resident spouse. See link below:

Nonresident Spouse Treated as a Resident (http://www.irs.gov/businesses/small/international/article/0,,id=96370,00.html)

I agree. I was mistaken. FICA taxes should not be due.