@ckwangt @naran79
As mentioned in that answer @ckwangt mentioned and guidelines for Non Resident Alien Spouse , the non-resident alien spouse on F1 or H4 is exempt from Medicare and SSN as follows,
'for Social Security and Medicare tax withholding purposes, the nonresident alien may still be treated as a nonresident alien'.
But guidelines for Alien Employees in the U.S. - Social Security Taxes mentions that,
'The exemption does not apply to nonimmigrants in F-1, J-1, M-1, or Q-1/Q-2 status who become resident aliens for tax purposes'.
So my interpretation says, the spouse on H1 will become resident and have to pay Medicare and SSN for whole year. I still need expert advice on this. This answer mentions 'FICA taxes are just between you, employer and govt, meaning employer takes definite amount from your paycheck and send to govt. If they didnt withhold in your case thats correct. You dont need to worry about it.' So its quite confusing.
In my case, if my spouse on H1 has to pay these FICA taxes from Jan 1 to Sep 30, there is no benefit in filing jointly. It would be better to file separately as Non-residents in that case.
