I didn't FICA for 12 weeks

[HexaDash]

I did not pay FICA tax for 12 weeks. I was on an F1 visa when I did not have my Employer deduct FICA from my paycheck. Now my status changed from F1 to Permanent Resident. After my status changed, I had my employer change my tax exemption status and I started paying FICA. But I am afraid that now that I am a permanent resident, I will owe FICA for the whole year (since I and my SO are planning to file joint taxes , SO is US citizen).  Will I get penalized for not paying FICA before my change in status and if so, how do I ensure that I don't get hefty penalties. If I were to pay FICA in the months I was on an F1 visa, I would've paid around $1500 in FICA.

[rjs]

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@HexaDash wrote:

. . . I and my SO are planning to file joint taxes . . .

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I'm not sure about the answer to your FICA question, but if your "SO" is not your spouse, you cannot file jointly. Filing a joint tax return is only allowed for couples who are actually legally married as of the end of the year.

As I said, I'm not sure about the FICA, but generally the employer, not the employee, is responsible for withholding the correct amount of FICA tax, as long as the information that you put on your Form W-4 was correct at the time that you gave it to your employer. If you were properly exempt from FICA for the first 12 weeks of the year, then you don't owe the FICA tax for that period of time. Becoming subject to FICA later on is not going to change the fact that you were exempt earlier in the year. The IRS will not expect you to pay FICA taxes for the time that you were exempt, even if you became subject to FICA later. The determination of whether you have to pay FICA taxes is not a single decision for the entire year. It's determined separately for each job and each paycheck.