Hi ,
I have a situation where my employer did not deduct the social security and medical taxes (FICA) but only withheld the federal and state taxes. My understanding was I should need to pay these tax only when I shall receive my green card.

I moved to work for the company in the US in mid 2004 by internal transferring (same company where I worked outside the US) then I moved to work with the same company in the UK in mid 2004 and moved back in mid 2005 to work with the same company again.

I was granted green card in April 2006 and enquire on the FICA tax and I end up with back tax which the company HR asked me to pay from mid 2005 till present (around $13,000). I have the following questions.

1) Should the company responsible for the mistake of not deducting and submitting the FICA tax?
2) What will be the company responsibility in this case?
3) Should I revoke that the FICA tax needs to be paid started from mid 1998?
The total amount will be around $40,000. The company may advance this money and deduct from my salary (same as the amount of $13,000).
4) Will the Social Security Department or IRS find out and come after me later?
Will do I need to pay if, let’s say, I move to work with another company?

Salary from mid 1998-mid 2004 is 52K - 68K.
Salary from mid 2005-present is 77K-80K.

As the FICA will reflect the social security support from government, if this still possible, I kind of think that the FICA tax should be paid start from the beginning as not only my money but also the company need to match that amount.

I do appreciate all answers.

Thanks,

Atlanta05